Solid check engine light

[Mike Kelly]

Need some guidance:

6/91 stock with just y-pipe. 300K +.

A solid check engine appeared yesterday. Cars starts and runs fine. I tried pulling the codes but got just solid light . The test made the normal sounds during the test. Disconnected the battery to reset no gain.

I changed the Ecu, maf, tps, ccrm, coil pack and air temp sensor with good working stock parts from my supply. No change to solid light but still starts and runs good.

Thanks Mike

 

[luigisho]

I assume you have been around and have the correct pic/diagram for correctly jumpering the plugs for fault codes. You are not using a store bought OBDI code reader correct? If you are using paperclip method, have you double checked your jumper slots to make sure they are the correct ones?

 

[Mike Kelly]

I assume you have been around and have the correct pic/diagram for correctly jumpering the plugs for fault codes. You are not using a store bought OBDI code reader correct? If you are using paperclip method, have you double checked your jumper slots to make sure they are the correct ones?

Yes Sir. Correct.

 

[luigisho]

Well that is difficult.

First guess--wiring short somewhere. I remember O2 sensor fault with solid light post over a decade ago. Maybe had an O2 ground wire issue. Also remember someone opening the harness and finding a faulted wire that gave a solid light without codes. This is all a long time ago and I can't recall the details. I hate electrical issues like this.

I think there have also been electrical issues with the instrument cluster printed circuits but this is all hazy spitballing and I don't have a high degree of confidence that solid MIL light was the issue surrounding that failure. Hopefully rubydist or someone has a good starting point here.

 

[Mike Kelly]

After all theses years with many Gen 1's this a new one for me. I also am leaning towards something electrical maybe harness somewhere. I just finished cleaning the upper grounds but nothing changed. The car is on stands I will change the o2 sensors just for good measure, can't hurt. Thanks Mike

 

[luigisho]

Just to be clear- I don't recall if the sensor, the sensor pigtail, or the wiring to the sensor had an issue. All the years gone by this stuff gets real fuzzy for low repeated problems.

 

[Mike Kelly]

I understand. Im replacing the sensors just because and also checking for any exterior wiring issues on anything I can see or reach. Thanks