ECT Analyzer/manual TC lockup

[Bruce]

I found this reference to an ECT Analyzer in some Toyota service literature...it looks like it'd be perfect for manually locking up the TC on my `99 Prizm (Corolla clone) rather than having to play games with the accelerator at moderate speeds:

http://www.autoshop101.com/forms/h17.pdf

Anybody know where to get one? Better yet, is there a way to hack what it does, ie. put the TC lockup on a switch?

- Bruce

[CO ZX2]

This is the sort of thought that could benefit many with auto transmissions. Heaven knows they need it. Kudos for bringing attention to the possibilities.

ECT Analyzer referred to is probably only supplied to Toyota. Toyota parts and service may be able to provide a contact.

I do know there are lockup switches available for some transmissions. May turn out to be as simple as splicing a switch into the lockup solenoid wiring. Found this site when looking around. May be of some help or ideas.
http://www.eng-tips.com/viewthread.cfm?qid=59308&page=7

Dig into this well before giving up. You could render a much needed service to others. Let us know what you come up with.

[Bruce]

More like:

http://www.eng-tips.com/viewthread.cfm?qid=59308&page=7 , I guess.

But the result is the same...I'll need a wiring diagram. I can get my hands on a shop manual for free, but I'll need to wait a few months for it.

[TomO]

Click on Drawing 1 in this LINK (http://arrc.epnet.com/autoasp/wireidx2.asp?cid=1&wname=Engine%20Controls&wss=&wopt=&wconf=1.8&sid=2752563&uid=s5531745.remote.autorefctr&ISDN=9306GEO&mk=CHEVROLET&md=PRIZM&yr=1999&Vid=1353608). It shows the TCC ctrl running to pin 21 of the transmission control module as a blu/yel wire. It looks like the module supplies with with a 12V signal since the other side of the solenoid is grounded. Just let me know if the link doesn't work for you and I'll fix it.

I used to control the TCC in my 90 Turbo Grand Prix VIA a switch on the TCC circuit to lock it up sooner. But that was back when I was doing it for acceleration reasons and not FE.

[CO ZX2]

TomO, when I click on LINK takes me to login and password site. Sounds like you are on the right track.

[Bruce]

Yeah, same for me...for subscribers only.

Any indication of a service plug that can be used, like the pictures in the original link for the ECT? I'd rather clip onto a plug than munch up the OEM wiring. Thanks --

[TomO]

Click HERE (http://www.powerlibrary.net/Remote/Remote.asp?ID=meadville) Then enter pl249412345678 in the space where it asks for the barcode number. Click Submit. Then click on Auto Repair Reference Center (near the upper middle of the screen under Auto Repair). Then click on the Auto Repair Center Link that shows up in the next screen. Select you year, make and model, then select the topic you want to cover. In Bruce's case, I chose 1999>Chevrolet>Prism>1.8L>Wiring Diagrams>Engine controls>diagram 1

It's a little work to get through but well worth it.

[Bruce]

Thanks!

[MetroMPG]

Interesting idea. Watching with interest...

[diamondlarry]

It wouldn't let me in. I got the following message.


--------------------------------------------------------------------------------

Important User Information: Remote access to EBSCO's databases is permitted to patrons of subscribing institutions accessing from remote locations for personal, non-commercial use. However, remote access to EBSCO's databases from non-subscribing institutions is not allowed if the purpose of the use is for commercial gain through cost reduction or avoidance for a non-subscribing institution.

[TomO]

Hmm, try once more and let me know.

[diamondlarry]

Still no luck.

[TomO]

weird. What info were you looking for? Maybe I can pull it up and send you a picture of it, or just tell you the info.

[diamondlarry]

As soon as I click on the Auto Repair Reference Center link I get the message I posted earlier.

[omgwtfbyobbq]

Edit- nvm, no cookies enabled.

[CO ZX2]

Still no luck.

Larry, I had the same trouble you are having but finally got thru.

I had to enable cookies for the site and enable Adobe Acro in add-ons, then it worked. CO ZX2

[diamondlarry]

weird. What info were you looking for? Maybe I can pull it up and send you a picture of it, or just tell you the info.

I was trying to see if I could get a pin-out diagram for my '99 Saturn's ECU. Saturn no longer has manuals at the dealer. They have went to an online only system.:(

[TomO]

ok Larry, check out this link HERE (http://www.powerlibrary.net/Remote/MainR.asp?ID=PL2494) and make sure that your browser is setup properly.

In the mean time I'll pull the pinouts for your Saturn and PM them to you.

[diamondlarry]

ok Larry, check out this link HERE (http://www.powerlibrary.net/Remote/MainR.asp?ID=PL2494) and make sure that your browser is setup properly.

In the mean time I'll pull the pinouts for your Saturn and PM them to you.

When I click the "Auto Repair Reference Center" on the page you just sent the link for is when I get the error message. I get sent to this page:
http://search.ebscohost.com/login.aspx?authtype=url&site=autorefctr&return=y Odd. Thanks for looking for the pin-out diagram. I'm specificaly looking for the pin that is responsible for the Keep Alive Memory. When I use my injector kill switch repeatedly the engine begins to idle very fast; sometimes as fast as 3,000 rpm's. If I pull the battery cable for a few minutes, everything goes back to normal. I eventuall want to see if I can't hook that up to the ignition switch so it re-sets everytime I start the engine with the key. Sorry about hijacking the thread.:o

[TomO]

I've PM'ed you about it Larry. And sorry for thread-jacking, I got carried away with helping everyone out.

[diamondlarry]

Actually, I think it was me that was the hijacker.:o Thanks for the help.:thumbup:

[Bruce]

Probably the first step would be to tap off the wiring or connector to an LED to at least have a TCC indicator. This'd be a lot safer than putting it on a switch, because leaving it locked could potentially stall the engine if the brakes are locked up to avoid an accident, and it may also be hard on the car if I put in too much throttle going uphill and the Powertrain Control Module downshifts the transmission. My thought is that I could just run a couple leads out the back of the hood so that a LED rests on the HVAC intake.

How can I locate the PCM? I have several fuse blocks under the hood.

[TomO]

the ECU on Toyotas (which is who actually makes most of the parts for your car) is usually located just about on the floor directly behind the center console. It may be just under the the backside of the center console as well (towards the dash). It's been a year since I've had to pull an ECU out of a Prizm so bear with me.

[Bruce]

Ugh.

If getting at the ECU wiring is anywhere near as bad as replacing a heater core, I'd skip it. Ripping the dash out is a lot of work, and I'd probably screw something up in doing it. (Take it apart, put it back together, figure out what to do with the parts left over.)

For an indicator at least, it sounds like tapping into the transmission end of the harness may be easier, though I'd need help finding that as well.

Thanks!

[Toysrme]

All it takes is a relay to ground the ECU's signal throguh a 10w resistor, and a switch to send 9-12v of current through the other side of the relay when you want / don't want the torque convertor locked up.
This idea would only help restarting the engine via the clutch during pulse & glide, which would be very harsh since it doesn't slip... It's either on, or it's off...

In actuality. This wouldn't help you hardly at all. Via the TCCU logic, in any gear near an overdrive gear (3&4th on a 4 speed, 4 & 5th in the 5-speeds & 4-6 in the 6-speeds.), anytime the VTA signal reads <5% of the previously measured vta signal, the torque convter is locked to begin with, provided the engine is warm.
Not only that, but OEM torque convertors are weak as ****ing piss. You'd have to spend $500-1000 to have your torque convertor custom rebuilt with a sick clutch pack, then swap, or pay it to be swapped out.







This is not something that will pan out. btw, you can build a complete manual controller via a 6-sway rotary switch for about $15 for any of the 4 speed Asian-Warner transmissions in the same manner as described above.




You also get into an unlocked torque convertor has more power loss, but you also have the mechanical benifit of it's flash speed, which has an absolutely gigantic short term impact in torque output when you're on the throttle. In the order of 1.8-2.0x torque output until it has caught up.

[rh77]

I have separate post on this subject and noticed this one...

Basically the TC on my '98 Integra 4-speed is very TPS-specific. I have the shop manual, pinouts, and flow-charts of the TC lockup condition (zero, partial, half, or full) and sensor requirements.

I'm not sure what's going on, but the TC will lock-up at 'full' when over 35% TPS, but as soon as it drops below that at cruise, it unlocks and re-shifts into partial at 20%, for example (I can't hold-on to it with less throttle).

All other conditions are in-place - a specific example today:

Coolant = Full Operating Temp (202F)
VSS reads 55+ MPH
Secondary Lock-Up Sensor is not showing "Hill Logic" override
Transmission Selector in Top Gear: D4
IAT in the high 80s


I don't have the diagram with me right now, but I can't determine if altering the electronic TPS signal will help, or if it's the actual TPS cable to the transmission that needs tightening.

Can anyone shed some light on a possible fix. I'm running down the highway in zero or partial lockup and it's killing my FE!

RH77

[MetroMPG]

RH77, not to rub salt in the wound, but remind me again why you're driving an auto? Is it for the other driver in the house?

[rh77]

RH77, not to rub salt in the wound, but remind me again why you're driving an auto? Is it for the other driver in the house?

Ouch...Salt.

Yes, my wife can't/won't drive a manual. I resolved to driving her old car to save on a car payment and to have 2 autos around the house so it can be driven by either party.

The next solution would be to trade the 'Teg on a different, more fuel-efficient automatic. The problem is that the car holds sentimental value from an untimely death in the family, and is a touchy subject to discuss selling it.

-RH77

[MetroMPG]

Okey dokey. Just wondering. (You probably already mentioned this when I wasn't paying attention.)

[SVOboy]

I have separate post on this subject and noticed this one...

Basically the TC on my '98 Integra 4-speed is very TPS-specific. I have the shop manual, pinouts, and flow-charts of the TC lockup condition (zero, partial, half, or full) and sensor requirements.

I'm not sure what's going on, but the TC will lock-up at 'full' when over 35% TPS, but as soon as it drops below that at cruise, it unlocks and re-shifts into partial at 20%, for example (I can't hold-on to it with less throttle).

All other conditions are in-place - a specific example today:

Coolant = Full Operating Temp (202F)
VSS reads 55+ MPH
Secondary Lock-Up Sensor is not showing "Hill Logic" override
Transmission Selector in Top Gear: D4
IAT in the high 80s


I don't have the diagram with me right now, but I can't determine if altering the electronic TPS signal will help, or if it's the actual TPS cable to the transmission that needs tightening.

Can anyone shed some light on a possible fix. I'm running down the highway in zero or partial lockup and it's killing my FE!

RH77
On the CRX, there is only zero and full lockup, and full lockup can be induced by giving the wire running from the ecu to the solenoid a constant 12V. Meaning, it will lock up when it gets warm if it is getting the 12V, but not otherwise. It's odd that it doesn't stay always locked up, but that's the case. You could attempt through a switch in line with the full lockup wire and a 12v source and seeing if it will activate lockup when you're on the highway. Either that our you could neutral bomb the transmission and swap in a stick, :p

[rh77]

I'd love to find a low-mileage HCH-I/Manual, but ya know... :o

RH77

[rh77]

On the CRX, there is only zero and full lockup, and full lockup can be induced by giving the wire running from the ecu to the solenoid a constant 12V. Meaning, it will lock up when it gets warm if it is getting the 12V, but not otherwise. It's odd that it doesn't stay always locked up, but that's the case. You could attempt through a switch in line with the full lockup wire and a 12v source and seeing if it will activate lockup when you're on the highway. Either that our you could neutral bomb the transmission and swap in a stick, :p

I like the latter idea, wait no... :D

From the shop manual, this isn't like the old Hondas. It actually has 2 lockup solenoids and a series of condidtions for each. The first (A) is straightforward and handles partial and half lockup based on the usual sensory inputs as interpreted by the TCU. The Second (B) handles the "Hill-Logic Control" and engages Full-Lockup when Sensor A is in agreement and enough fluid pressure is available to do so. Each run on a 5V system from the TCU.

It seems to work, but under inefficient and slightly flawed conditions. That magic number of 35-40% TPS kicks it right-in, but lift (even slowly) and it unlocks. That's the rub...

RH77

[SVOboy]

Low mileage is for suckas.

[rh77]

Low mileage is for suckas.

Paint me a sucka -- I don't want the batt-pack failing after a short duration.

I agree though, with gassers and especially Diesels -- mileage schmileage.

RH77

[cfg83]

rh77 -

Ouch...Salt.

Yes, my wife can't/won't drive a manual. I resolved to driving her old car to save on a car payment and to have 2 autos around the house so it can be driven by either party.

The next solution would be to trade the 'Teg on a different, more fuel-efficient automatic. The problem is that the car holds sentimental value from an untimely death in the family, and is a touchy subject to discuss selling it.

-RH77

Ooooof, sorry to hear that. The politics of life. I won't make my wife drive stick, and she won't make me get an automatic, which is fair by me. We have reached transmission-détente.

If there is sentimental value, I would keep the 'Teg and install a stick at the best opportunity. If you bide your time, you should be able to get a manual transmission installed on your terms and at your price. That way, the only sacrifice is inter-driveability.

CarloSW2

[cfg83]

rh77 -

I'd love to find a low-mileage HCH-I/Manual, but ya know... :o

RH77

The ONLY hybrid I would consider owning.

CarloSW2

[rh77]

This was so freakin' simple I'm sick over it.

The throttle cable linkage to the transmission was loose.

It took 5 minutes to tighten.

Test Drive: TC full lockup, 55 mpg at 60 mph on the highway, at 2000 RPM instead of 40 mpg at 3000. I'm cruisin' down streets at 1400 RPM at full lockup. If I only new months ago.

It does need some tweaking: it may be too tight as the shifts are a bit harder and TC stays engaged when I let off of the gas. But it LOCKED UP TIGHT!

Boo-yeah.

RH77

[MetroMPG]

Awesome. Expecting a 15% minimum improvement on your next tank ;)

[rh77]

Awesome. Expecting a 15% minimum improvement on your next tank ;)

Thanks man...

BTW I'm at 1/4 tank with a 104 mile round-trip expected this week. Let's see if I can make it :cool:

Then we'll talk percentages on the next tank :D

Honestly -- if I knew this a year or more ago.

Thanks to Bruce for the post (and Toysrme for resurrecting it)! I looked through the Toyota manual linked in the first post, and it referenced the tightness of the throttle linkage. I thought, "what the heck" and gave it a look-see. Sure enough!

RH77

[cfg83]

rh77 -

This was so freakin' simple I'm sick over it.

The throttle cable linkage to the transmission was loose.

It took 5 minutes to tighten.

Test Drive: TC full lockup, 55 mpg at 60 mph on the highway, at 2000 RPM instead of 40 mpg at 3000. I'm cruisin' down streets at 1400 RPM at full lockup. If I only new months ago.

It does need some tweaking: it may be too tight as the shifts are a bit harder and TC stays engaged when I let off of the gas. But it LOCKED UP TIGHT!

Boo-yeah.

RH77

Sounds like my "tappy valves" that were actually a loose headlight adjustment screw. I'd been driving with heavy 20W50 engine oil for over a year because of that stupid screw.

Screwed by a (loose) screw.

CarloSW2

[Silveredwings]

Oh, Man!! :(

[itjstagame]

We're trying to sell the GFs automatic and she's open to me teaching her to drive stick. But I know that'll cause her to just get confused and crash :-).

[Bruce]

After doing some more thinking and research in my Haynes manual, I located the wire for the TCC solenoid at the transmission end this weekend. To make sure I located the right one, I wired up an LED and pullup resistor to a pin and ground lug, pushed the pin through the wire insulation and routed the LED through an opening in the left fender so it's visible through the windshield.

I finally drove the car this morning, and it worked perfectly -- no harm done, and the LED lights up when the TCC locks up.

I confirmed on the way to work that the TCC unlocks whenever there's no pressure on the gas pedal (it's apparently released by the brake switch on some other cars.) I still need to confirm that the TCC doesn't lock in 3rd, which I'll do on the way home.

The next step would be to splice in a rectifier diode in series with a wire on either side. Upstream of the diode would go to the LED; downstream would go to a momentary-contact switch on the shifter, and from there to 12V. This should allow me to manually lock up in 3rd in the ~27-39 MPH range or 4th in the 39-45 MPH range.

I'll need to confirm that the PCM is sending 12V and not 5V before wiring in the switch; I should be able to do this using the switch lead and a DMM.

Most of the speed limits around here on secondaries are in the 25-35 MPH range, so it should buy at least an extra 1-2 MPG. It'd make the biggest improvement in FE when climbing hills at 30-35 MPH. I also wouldn't need to pulse to 45 MPH to lock up the TCC for cruising at 40, which should reduce the risk of a speeding ticket.

The PCM limits the maximum gear to second and third below water temps of 101°F and 137°F respectively, so using the TCC switch could also help efficiency during warm-up.

The LED upstream of the rectifier would let me know when the PCM is sending a lockup signal so I could let off the switch at highway speeds.

I expect keeping the TCC locked while shifting would be detrimental to the powertrain's reliability, so I'd plan to limit the speed, throttle and gear selection to make a shift unlikely while the TCC is locked. Putting the switch on the gearshift should help avoid an accidental shift in lockup, since I'll need to let it go to change gears.

I'm looking forward to installing this and trying this out. It should add a whole new dimension of hypermiling fun to my commute, while still leaving the car driveable for anybody else.

[2TonJellyBean]

Bruce - perfect!!!

I wish I had both the skills to do that as well. :-/

[MetroMPG]

I'm impressed. Good work Bruce. Looking forward to the next update.

[Bruce]

I'm impressed. Good work Bruce. Looking forward to the next update.

Thanks, but this is peanuts compared to the stuff you're doing. :D

[MetroMPG]

Not really. I'm macro, you're micro. I had to look up "pullup resistor" :)

EDIT: and by that, I mean I bet you've got a finer understanding of these things than I have.

[Bruce]

I tried keeping it in 3rd up to 45MPH on the way home last night...the PCM locked the TCC around 42 MPH, maybe 1-2 MPH less than when it'd normally lock up in 4th. The PCM lockup signal appears to be a function of engine load (at a given RPM) and speed, regardless of the gear selection -- I've occasionally gotten it to lock up in 4th at 42 MPH when I really feather the accelerator.

It would definitely benefit from manual control. I have a friend with a Saturn sedan; his AT locks up in 3rd at low speeds when 3rd is manually selected, so it should be okay on this car.

Given csrmel's thread on the Chrysler a604, I'll definitely need to check the voltage/current output with a DMM before I start hooking up an override switch.

[Bruce]

I finally hacked into the wiring last night. I hated to splice into the OEM harness, especially given it's location, but it's the only way I had to accomplish what I wanted. It's my car, darn it, and the warranty is long gone anyway.

The connector for the TCC wire is right behind a gap between the splash guard and left fender, forward of the front wheel -- perfect for getting hosed down with water. :( I cut the wire, spliced a long piece of ~12 AWG speaker cable onto the ends (to minimize added impedance), shrunk some heatshrink over the solder joints, ziptied the speaker cable to the harness and wrapped everything with electrical tape. Hopefully, it'll be good enough. I may go back later and dab some RTV onto the ends of the heatshrink to ensure they're sealed, but I don't want to redo the solder joints -- there's not much free wire on the harness to work with, and it's in a tight location.

For now, I've routed the speaker cable along the fender, through a gap between the fender and door pillar, along the rocker panel and under the driver's seat to the passenger side. I'll probably eventually route it under the dash to the shifter instead.

I twisted the ends of the speaker cable together, hooked up an analog voltmeter and the TCC LED from last week to the joint, and connected the LED and voltmeter to ground.

As of this morning's commute, everything is still working as expected. At lockup, the LED comes on and the voltmeter is indicating alternator voltage (~12-15V), so everything is still working and now I can see that the computer is feeding 12V. Whew. :o Now that I have the wiring remoted to the interior, it'll be a lot easier to play around with it.

Unfortunately, this morning's was another commute that would've been perfect for a lockup switch -- I was following somebody uphill at 35 MPH and getting 22 MPG instead of 30 because the converter was unlocked. :(

When I got to work, I hooked up a DMM inline on the 10A range; I'll check out the current draw on the way home.

After that, I can check the impedance of the solenoid; on Thursday's drive, I'll check for any AC waveforms in the lockup signal with an amplified speaker. So far, it just looks like a simple 12V will work for an override switch, but I want to be absolutely sure.

[Bruce]

Current draw is ~1.0±.03 Amps DC. I'll set up the speaker tonight to check for AC waveforms.

The cable I used appears to be 16 AWG (26/30); at a current draw of 1 Amp, 20 feet would come to a voltage drop of about 90 mV. If I'd used the 22 AWG used in the harness instead, the drop would be more like .3 V, which is starting to get significant -- especially if I wind up using a .6-1V diode in series as well.

The scary part will be the current draw from the solenoid when breaking the circuit -- it should easily be several amps. :eek:

[rh77]

Great thread. Keep us updated on the progress :thumbup:

If I ever take the plunge into hacking the TCU, the voltage drop and wire gauge considerations are good tips. So far, I haven't had to consider this aspect -- just supplying juice to various applications has been easy.

I too, look forward to the progress. (I'm also envious of the single-wire lockup command). :o

RH77

[MetroMPG]

Bruce: thorough work. The suspense is killing me. :D

[MetroMPG]

The scary part will be the current draw from the solenoid when breaking the circuit -- it should easily be several amps. :eek:

Is it Hallowe'en scary? What is your concern there?

[Bruce]

Is it Hallowe'en scary? What is your concern there?

Frying switches, maybe burning fingers. I found a couple of 12V relays in my parts bins, so I should be able to use those for breaking the circuit instead. I should be able to use these for a crude but safe logical "or" of the PCM and external switch signals by putting the switch ends of the relays in parallel between a 12V source and the TCC solenoid.

I finally "listened in" on the converter lockup signal this morning. (I've been biking quite a bit more lately, so it can be a while between experiments.) I took an old earphone, soldered a 1KOhm resistor in series and hooked it up to TCC and ground. A pop at engagement and faint, noisy whine while engaged. The noise sounds exactly like the noise you get on the AM band -- it rises and falls with engine RPM -- so I have to assume it's just plain old noisy 12-15V from the alternator, nothing fancy. So, it appears okay to feed it straight 12 Volts.

Next will be finding a line to tap for 12V, ~1.5A. The cigarette lighter should be a good candidate if I can get at the back of it, since it's already pretty close to the shifter.

I need to find a cleaner way of routing the wire to the interior. Quite a bit of it is exposed along the hinge area of the driver's door when the door is open.

[Bruce]

Duh! How about plugging into the lighter socket instead of tapping 12V permanently? Hmmm....

I could connectorize the TCC cable and run it up through the ashtray. Put the relays, switch and some LEDs (for power, PCM lock signal and manual lock signal) into a small project box with a couple of pigtails for the TCC cable and 12V lighter plug. Velcro the box anywhere it's convenient to use.

If I make up a jumper for the TCC connector, I could then just unplug and remove the box, plug in the jumper and tuck in the connector end whenever I need to lend the car to somebody else (usually my wife). Voila, the car is stock again with no mystery buttons.

I like it. It's a solution I can visualize, and it should be relatively easy to implement.

[Bruce]

I didn't have time to wire up a couple of relays, so I wired up a simpler circuit last night: a Schottky diode (.525V forward drop) between the PCM lead and the TCC lead, and a heavy-duty switch between the positive on a cigarette lighter plug and the TCC lead. I also left the LED and pullup resistor between the PCM lead and ground.

Just to make sure everything had power, I measured the current of the solenoid with ignition on across the switch leads. 1 Amp, as it should be, and the coil inductance made nice sparks when disconnecting.

I drove to work this morning; I never used the switch. I coasted down to the end of the street, as usual, fired up the engine and the CEL stayed on.

After coasting to a stop, I restored the wiring to its previous configuration, and went for another burn. The CEL stayed on, so I pulled into a parking lot to check and clear codes. The code was for Transmission Shift Solenoid E, of course.

I drove to work without further incident. Everything still works fine.

My best guess is that the PCM is checking for opens/shorts on the TCC solenoid by using a voltage divider. It probably leaves a high-value resistance between the TCC output and +12V; if the TCC output is greater than a certain threshold (say, 0.1V), then it throws a code. Apparently, the 0.525V added by the diode isn't low enough.

I can probably get around this by using a big, low-value resistor to ground in series with a relay coil for switching the TCC. Unfortunately, that means drawing an additional 12 Watts from the alternator over the stock configuration when the PCM normally switches the coil, e.g. above 45 MPH. I'm not sure how much impact this would have on FE, but it certainly won't help.

I guess the first step will be to find out how much resistance (how little power) I can use between the PCM output and ground without throwing a code. With any luck, I may be able to keep it down to a Watt or two.

I'm hoping the PCM will throw codes without starting the engine so I don't have to idle while trying different resistance values.

[Bruce]

I'm hoping the PCM will throw codes without starting the engine so I don't have to idle while trying different resistance values.

No such luck, unfortunately. After work, I pulled apart the PCM output and TCC lead, turned to IG-II and put it in drive. No codes without starting the engine.

I'll hook the relays up this weekend and put a 12 Volt, 11 Watt lamp between the PCM output and ground to spoof the PCM. If that works, I also have 7 Watt and 4 Watt bulbs for the same fixture that I can try.

A resistor will have better long-term reliability, but the bulbs are easier for testing.

[Bruce]

I wired up a circuit today with a couple of relays, a couple of resistors, an indicator LED, the 12V light, a momentary-contact pushbutton switch, a cigarette lighter plug and some leads for the PCM input and TCC output. I tested everything on the bench before hooking it up.

It appears to work properly. It definitely lowers the engine speed in second and third at lower speeds and applying more gas doesn't raise it immediately. The TCC locks up normally at ~44 MPH as usual, and the light comes on.

The only problem is that I'm not sure it's gaining me any FE. I think it's a matter of using it judiciously and learning the speed ranges where it'll help. There's a large speed band in the 35-45 MPH range where it's probably better to leave it unlocked in 4th than locked in 3rd as long as I'm not going uphill.

I only got 33 MPG on a short drive this evening (8.3 miles), but it's only around 40°F or so. The car didn't have much of a chance to warm up.

I need to move the pushbutton to the shifter so it's more convenient to use.

[Bruce]

I unplugged the lamp on the way home Sunday morning. No codes. The PCM appears to be happy with a 450 Ohm resistor and the relay coil in parallel.

Surprisingly, it's looking like I'm better off not using the switch during warmup. The couple of times I've tried it, overall FE seems to be worse and I've watched the instantaneous MPG go down when the TCC is locked up. I guess the engine gets slightly better FE at higher RPMs when it's cold.

It is nice for cruising, though. I can keep it locked at 35 MPH in 4th at low throttle, which is great for most roads around here. If I need to accelerate up a hill at 30-35 MPH, I can throw it in third and lock it up. It's also nice for accelerating in 4th, since I can lock it up right away and not need to back off to get the PCM to engage the TCC.

Acceleration with it locked feels much stronger, although there's a fine line between strong acceleration and lugging the engine at low RPMs. I've learned to not lock it up unless the engine is turning at least 1500 RPM under light load; otherwise, I'll lug the engine.

But, hey, it's possible to lug the engine -- what more could a FE nut want with an auto besides bump starting? :D

[Dust]

I can't access it right now, but the Australia Hilu Surf Owner's site has alot of info about lockup switches for the 3.0L diesels and trans.

[dkjones96]

If my engine and transmission computers were seperate like my old car I'd try to do to it what I did in my old Toyota Cressida. At idle the ECT would get no TPS signal so if you disconnected that input it assumed idle all the time. It would shift so early you'd be in overdrive with a locked torque converter by 35mph turning 1250rpm regardless of the throttle position if you just went into drive.

Was okay for that car since the L6 pulled just fine between 1000-2000 rpm, I don't think these little 4 bangers would like that.

Worked wonders for in-city fuel economy but since it never got told TPS you couldn't just floor the car on the freeway and expect her to get out of her own way. You could manually shift the car which I usually preferred but it got old after a while.