I have a 1991 Volvo 940 Turbo. Great car to drive and still in good condition, however, I need to figure out how to clear the check engine light in order to smog. I ran OBD and got two codes - 1-2-3 and 2-2-4 indicating a ground fault problem and ECT sensor. Code 2-2-4 causes hard cold starting. I've replaced the ECT sensor but to no avail. It still gives me the same code. I have noticed other items that may cause the check engine to light to come on. I noticed the fuel gauge and speedometer not working properly as well as ****ty radio wiring. The shift indicator is also illuminated constanly. I replaced the fuel filter and rewired the fuel gauge light. fuel gauge working excellent now. I found a cheap ECM and replaced that as well. I still need to work on the speedometer sensor. Crank engine sensor and battery are working well. Can anyone please throw in any suggestions? The pros now is that the check engine light can now be resetted compared to prior - at least briefly.

 

Just disconnect the battery for 20 minutes. This will clear the CEL providing all is well with the systems. If not, it may pop up again pretty quick. By the sound of it, you may have a bad Circuit Board behind the instrument panel OR bad ground.

 

Thank you Lev. This problem has been on going for almost two months. I have been only disconnecting the battery for 2 seconds after installing the new ECM. I will try to disconnect it for 20 or more. The ignition system module behind the brake/acclerator pedal is my next suspision if this doesn't work. Any suggestions on this.

Thank you for your post. It is much appreciated.

 

I see you're in Colorado? Most states do not require the CEL to be off except for 96+ cars with OBD II. Are you certain it needs to be off in your state? For your era vehicle, you could simply remove the light bulb from the cluster...it isn't as if the computers are as sophisticated as later OBD II cars. Both those codes lead to the ecs. You're right; when it fails, it will either tell the ecu it's about 60 below and it will run pig rich or it will default to normal and just be difficult to start when cold. Be advised, rich running engines kill O2 sensors and catalytic converters quickly! If you search, you'll find several recent threads on replacing the ecs.

 

Thanks for the reply. Sorry about my late reply. I still have the cold start and check engine light problem. I switched the ecm but still got the same problem. I do notice the speedometer jumping around quite a bit. Could this be related to the grounding problem? I'm just throwing things out there at this point. Any advice will do. I was thinking about replacing and rewiring the ignition system or engine harness. I suspect the ground problem is causing my check engine to light up as well as the hard start when cold issue.

 

Make sure it isn't something funny in your instruments....I have an intermittent issue with mine....some information and power goes through the cluster...I'd examine that if nothing else seems to be fixing the problem