How to diagnose problem. Truck runs and sounds ok but ECM derates to 1500. What? where? to look. I know 331 refers to #2 cylinder injector harness low or insufficient voltage. Thanks for any advice.
Ok. Before I did any work. My motor had an intermittent miss. I had this happen before and that is when I changed (july) the 5 and 6 pass thru and injector harness. Couple days ago coming home the motor felt like it would not accelerate into full power. BUT it did not show any codes. This is why I thought changing the pass thru and injector harness on the 1 and 2 cylinder because that fixed it last time. I just finished putting the old harness that worked(the plastic connector broke is why I changed the injector harness inside motor) It still gives the same code. Of course I can not start motor as it is apart. Does just disconnecting motor reset codes? How can I test injector harness to make sure it has the correct amount of voltage or amps? After I did this work. The motor sounded fine. No misses, smooth idle and acceleration Up to 1500 rpm. Thanks
There is no test for voltage or amps, you would disconnect the injector harness at the ECM, and then disconnect at the pass through and measure the wiring for continuity and for shorts to ground or other circuits. A good test to check the strength of the wiring is supply power through it and connect the other end to a head light bulb and then ground the headlight. If the wiring can supply enough power to brightly light a headlight bulb, then it will carry enough amps to run an injector no problem. Then, once the light bulb is lit, you wiggle the harness inch by inch to make sure there are no broken or weak spots inside the harness. After that, to confirm a bad injector, you can simply take out #1 and #2 injectors and then reinstall the #1 injector into cylinder #2 and put injector 2 into cylinder #1 and retest. If your code changes to #1 circuit, now you know the injector is bad, if the code stays the same it is wiring or the ECM itself.
I have to pay someone to do overhead. I lack the confidence/knowledge and experience to do this myself. I got a new injector. Installed it in the 2 cylinder. Waiting until tomorrow to have overhead done. Question? When I key on again the same code is still coming up. I have disconnected the power supply for about 20 minutes. Reconnected but until the overhead tomorrow I can't try to start. Does disconnecting batteries or just with key on reset the codes without actually trying to start the motor? Or do I have to connect to the insite program to reset. Does the new injector have to be registered in to the ECM. ECM was changed about 6 monthes ago. Rebuilt from Cummins. Thanks
When you run engine and ecm is satisfied that proper repair is made, the check engine light will go out, but the code will remain in memory until it is erased with insite. It may take 10-30 seconds.
Thanks for the advice. What a depressing 30 seconds until the yellow CEL turned off, after starting motor. I changed the injector and now when I "mash the gas" there is no hesitation or misfire. Before this repair I had to be real nimble with the go pedal. Slower than slow acceleration to prevent the misfire. Not having a code show on the dash, made it difficult for me to figure out what the problem was. I guess after changing the pass thru let the ECM see the bad injector solenoid. Hopefully no more questions until I overhaul the motor this summer. Thanks again.
