This morning while warming up the truck before hauling my trailer the CEL came on and the truck started to idle really rough. The engine continued to run very rough as throttle was applied. I checked the codes and there are none but the CEL is on. At first it would run smooth for a moment, CEL would go off and then it would come back on and run rough again. My Pyrometer was pegged in the red or jumping all over the place while the truck ran rough. After starting the truck several times and cleaning codes the batteries would not turn over the truck so I replaced the batteries as they are 5 years old and I figured it was time and that could be the problem. After replacing the batteries I have the same issue with the CEL but the Pyrometer was no longer acting up. Pulled a code P0603 because the batteries were out, cleared the codes and tried replacing the CPS with the same results. Next I pulled the chip out of the PCM and had the same results. Checked all the connections under the hood and I am still getting the same results. Truck starts, CEL comes on a few seconds after starting and runs REALLY rough.

I am at a loss on what to check next. Anyone run into this situation and have a suggestion on where to look next for this problem?

Thanks!

 

Did you check your valve cover gasket harnesses for melting?

 

There should be a code present if you are getting a CEL. I'd start checking the UVC wiring and pigtails on the harness.

 

I went through all the valve cover gasket connections on the outside. No melting at the plugs. I have not pulled the valve covers and looked at the underside yet.

 

There should be a code present if I am getting a CEL but there isn't! That is what is so strange.

 

Thats crazy, mine did the same thing this week. CEL but no codes. You know Daniel B. in Gunnison?

 

That means your code reader isn't compatible with your truck, if that CEL turn on even if it turns off you will have a code.

 

My code reader is compatible with my truck. As I've been using it for 15 years. After pulling and replacing the batteries it gave a P0603 KAM code and when I first checked it after the CEL went on I had the P0236 MAP Sensor code that I always get since the truck came out of the factory. I have never encountered this problem or seen a CEL not leave a code. After clearing the codes and starting the truck again CEL comes on and the only code stored is the P1111 code saying everything passes...

 

There is a stupid fuel sensor on the driver side head. Cost about $140


Un plug the wire from that thing and see if it changes the engine idle any.


ReBill came down here and checked my truck and that is one thing he did before hooking up his computer to it.
His computer program showed that it was the problem....I bought Mine from Riffraff


I am sorry I can not remember the name of that thing.....I can look back into my post from last fall and see the name of it

 

Icp is what youre looking for I believe.

 

The ICP sensor was replaced not too long ago - it threw a code when it went bad last time and made the truck surge not run like it was missing. It was one of the first things I checked along with the CPS.

Just ran a BUZZ Test on the injectors. They all sound great - no problems there. After the BUZZ Test the scanner that ran the test did come up with a P0264 error code. Before the BUZZ Test the other scanner came up with the same P1111 code.

 

Do a buzz test then scan for stored codes without starting the engine.

 

When we did that it came up with the P0264 error code.

 

IDM stores codes for injector related codes. After a buzz test the IDM will report any detected issues on the CID line to the PCM, a single communications line between the PCM and IDM. In this case P0264, injector #2 low - shorted to ground, or at least the IDM thinks so. The IDM will shut that cylinder down to protect itself.

 

Thanks, that's helpful. It does seem to be running like it is missing a cylinder. I was starting to think it was a bad injector. I will pull the wiring harness at the IDM and test the resistance in the wiring for injector #2. #2 buzzed fine during the test but I wonder if there isn't something mechanically wrong with it or it is simply worn out/broken after 312,000 miles.