Hello,

After driving my truck for 15 min the CEL comes on. No loss in power or any other indicator there is an issue. I have replaced all the vacuum lines, new O2 sensor and just about checked every damn connection i could find. If i turn off the ignition key and restart the CEL is off and will not return until another 15 min or so. Bad gas cap?? Only thing i can think of at this point.

I have tried to diagnose this with the diagnostic box code but no faults.

 

Replaced the fuel cap to OEM and still after driving 15 or so minutes the CEL comes on. I am at a loss. I ddo have an after market exhaust with aftermarket o2 sensor so maybe thats my next hurdle. Any input would be nice. thanks

 

The next time the CEL comes on, leave the truck running and jump the diagnostic ports. There should be a numerical code that will blink out.

 

Checked with the engine running so the CEL stays on (always turns off when i restart the car and then appears after 15 min)

I get code 12 engine revolution signal missing

I have new NGK wires, plugs, new distributor, checcked the grounds ar the ECM and still light wants to appear after driving for 15 or so min.

No loss in power, no issues at all. The truck runs like a top but that damn CEL bothers me everytime it appears.

Any thoughts?

 

A service manual is going to point you in the right direction. It’s likely a wiring, distributor or igniter issue. Maybe even the ECU itself.