knock and purge control valve codes
 

Anyone ever have these two codes keep popping up even though the wires check out fine and the sensors as well? I built the engine and dropped it in, got the codes and got tired of diagnosing it so I took the harness out and stripped it right back to the ecu, replaced any and all broken or crusty wires and clips. Tested it for continuity re installed it and the car ran fine for the entire day. Then the customer comes to get it and the code came back.I've replaced the knock sensor with one that I tested and is known to be good, (even though the old tested fine as well)I clear the code and drive the car for 10min then all of a sudden the code comes back and it goes into limp mode. So then I installed a pfc and hooked it to the laptop and it shows the knock sensor is working just fine. The car runs and drives beautifully with the pfc. I even tried another stock ecu after and same codes came back. Is it just that the stock ecu is sensitive to resistance in the harness? Any input would be much appreciated. The customer really doesn't want to purchase a pfc at this time.

Brent

I had a code for a bad fuel pump relay and everything checked out fine except the ECU had gone bad. Did you swap with the exact same model? Every year had changes in the ECU.

The car is a 94 and I tried a 93 ecu and got the same codes. I even connected a knock sensor an inch from the ecu and tested the wire for contunuity, grounded the sensor and plugged the ecu in, still the same thing. I thought it was the ecu as well but to get the same code with a different ecu seems unlikely.