I’ve been having hell with my ‘99, it’s a 2500 4x4 with an automatic trans. 130,000 miles all stock except for a few cosmetic things. One day out of the blue the trans went into limp mode, I hooked up my scan tool and I didn’t have any communication with the transmission. I started checking wiring harnesses and senors on the transmission. Found the output shaft speed sensor was bad so I replaced it and now the truck shifts 1-3 but has no O/D. It’s not my daily driver so I let it sit for a few days and came back to it when I had some time and I noticed it wasn’t charging the batteries and the A/C wasn’t working either. I wanted to verify that the it wasn’t each system failing at the same time and I jumped the a/c clutch relay and the a/c began cooling. The alternator tested fine so I put an external voltage regulator in the alternator and it began charging. I added a switch to the trans relay and the O/D solenoid engages. I was leaning towards the PCM being failed so I checked the power and ground to the PCM and it had both and no communication with the pcm and no codes so I ordered a rebuilt one ($600) and when I installed it, I still have the same issues. I’m at a loss here, how does the PCM know to turn accessories on? I was told that the CKP sensor is how the PCM knows the engine is running and turns everything on. I had an intermittent No start, and no tach issue with codes for the CKP sensor so I replaced it with an eichlin part. The engine starts and runs so the CKP sensor has to be good right? I also have replaced the APPS after a no throttle response issue and fixed that. I checked my 5v reference on the ECT and it was fine, that means the 5v on the pcm is fine, correct? Is there a way to check the CKP sensor without a Scope? I had a industry friend tell me that it could possibly be my batteries are toast (optima red tops). They’re old but the truck starts fine. Any help is appreciated, thanks guys.
I’ve been having hell with my ‘99, it’s a 2500 4x4 with an automatic trans. 130,000 miles all stock except for a few cosmetic things. One day out of the blue the trans went into limp mode, I hooked up my scan tool and I didn’t have any communication with the transmission. I started checking wiring harnesses and senors on the transmission. Found the output shaft speed sensor was bad so I replaced it and now the truck shifts 1-3 but has no O/D. It’s not my daily driver so I let it sit for a few days and came back to it when I had some time and I noticed it wasn’t charging the batteries and the A/C wasn’t working either. I wanted to verify that the it wasn’t each system failing at the same time and I jumped the a/c clutch relay and the a/c began cooling. The alternator tested fine so I put an external voltage regulator in the alternator and it began charging. I added a switch to the trans relay and the O/D solenoid engages. I was leaning towards the PCM being failed so I checked the power and ground to the PCM and it had both and no communication with the pcm and no codes so I ordered a rebuilt one ($600) and when I installed it, I still have the same issues. I’m at a loss here, how does the PCM know to turn accessories on? I was told that the CKP sensor is how the PCM knows the engine is running and turns everything on. I had an intermittent No start, and no tach issue with codes for the CKP sensor so I replaced it with an eichlin part. The engine starts and runs so the CKP sensor has to be good right? I also have replaced the APPS after a no throttle response issue and fixed that. I checked my 5v reference on the ECT and it was fine, that means the 5v on the pcm is fine, correct? Is there a way to check the CKP sensor without a Scope? I had a industry friend tell me that it could possibly be my batteries are toast (optima red tops). They’re old but the truck starts fine. Any help is appreciated, thanks guys.