CEL 48 issue on 1992 Civic VX

[Reborn996]

Okay, I have had this CEL since I bought the car a month ago. In trouble shooting it I have replaced the O2 sensor with a new 5-wire version and swapped out the CA ECU for a Fed ECU. No change... according to the Helm manual once these two items are replaced the only other way to get the code is a wiring issue between the O2 sensor and the ECU. Does anyone have an extra wire harness they can give me or even sell to me? I need to get rid of this CEL in order to smog the car...

Monroe, thanks for your help by the way! The ECU came in yesterday but the CEL is still there.

David

[jadziasman]

True, you could have a wiring harness issue. Did you follow the troubleshooting procedures for the open and short checks? This is the most likely source of your problem. If these checks came out OK, then it makes no sense to replace the wiring.

Code 48 indicates the LAF sensor is reading out of its normal operating range for some reason. It's possible you have an exhaust leak at the manifold or cracked manifold that is allowing air to enter close to the LAF. It's also possible that you have a misfiring issue. You could also have a fuel injection problem. And so on and so on.

Too bad it's not OBD2. The diagnostics are much better and make it easier for the mechanic to pinpoint the root cause of DTC's. In your case, it might be necessary to find a mechanic who has a digital storage oscilloscope (DSO) and exhaust gas analyzer (EGA). You need the DSO to check several of the sensors and the fuel injector pulse width. The EGA will help determine how lean or rich the engine is running currently.

[Reborn996]

Hmm, the helms manual does not state CEL 48 as a out of range reading but of a circuit or LAF connection issue... all of the troubleshooting is for wiring connections or faulty LAF/ECU. Nothing is said of misfire, exhaust, or injector issues which my car does not seem to exhibit anyways.

My problem with using the Helms wiring troubleshooting is it requires the test harness from Honda which is major expense. Is there a way to follow the Helms suggestions without the Honda test harness?

David

[Reborn996]

Fiddled with the connectors in the engine bay and it looks like the wiring harness connector from the ECU to the O2 sensor harness from the engine might be bad (the ones that connect on the passenger side shock tower by the battery). The sockets on the ECU harness side look bent up... tried to straighten it out and try again... but the CEL 48 is still there and now I also have a CEL 41 to go with it. Makes me think the ECU to Engine wiring harness might be the issue.

David

[Reborn996]

Oh, one more thing.... With the replacement Federal P07 ECU connected the cruise control light in the dash starts flashing randomly. My car never had cruise control to begin with and I do not think it was an option on any VX model. Another annoyance - why me......

David

[Reborn996]

Okay, problem fixed!!! It was a bad connection on the ECU harness where it connects to the engine harness by the battery. Played with the pins a little and cleaned up the sockets and now no CEL and I am getting lean burn!

Found out about the cruise control light as well... ends up the Federal P07 ECU supports a shift indicator light which my instrument cluster does not have. Guess I will be looking for a proper VX federal instrument cluster next.

By the way, I will be listing a barely used O2 sensor (5-wire) on the classifieds section. LOL

David