i have a 94 chevy k1500 i replaced the engine and now i have 2 problems, 1st is that i cannot communicate with the ecm, 2nd is at an idle and in gear the engine surges. Its only 50-100 rpm surge but once the egine is warm it is very noticeable. Any pointers on what to look at, replace would be appreciated. I have replaced egr valve, driver module, and all 3 solenoids on the left rear of the engine, along with the lift pump and filter.

 

What do you mean "can't communicate with the PCM"

No diagnostic mode when you short the pins or are you trying to use a real time scanner?

Figuring that out is step one....

 

when trying communicate with a scanner, solace, genesis, or even a newer matco scanner, none of them are able to access the ecm. I was able to run a jumper wire into the the dlc which brought up a code for the optical eye malfunction however, i have not been able to find anyone that can point me in the right direction to correct the issue.

 

Optical sensor is in the top of the ip.

Check to see if there an "optical filter" installed in the line. They have been known to fail. You can unplug it and plug the harness directly into the ip connector.

Check for filth and corruption on the optical sensor pins.


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hey, i found the issue with this truck, it was a fuel shut-off solenoid. i was looking at my other ip and decided to start switching a few parts well, it only took the one. thanks for the info