My 1993 Dodge Dakota quits running at any time, from right after start-up to going down the road. It wont start running again until the check engine light comes on when the ignition is turned on. I can sit there from a few seconds to five minutes before the check engine light comes on. I have cycled the key three times to check for a code, but there are none. I have checked much of the wiring to the relays and some to the PCM, but have found nothing wrong. This truck did the same thing with the two previous owners, and had the PCM replaced, to no avail. Any help would be appreciated.
" I have checked much of the wiring to the relays and some to the PCM"
That’s going to lead to 50 questions and “yep, I checked that” followed by 50 more questions about “how did you check it”
I’ll start - squirrelly ignition switch or ASD relay.
I have checked all the wiring to the ASD and fuel pump relays. It is the negative side which is controlled by the PCM that is causing the relays to turn off. Since the CEL does not come on, I have decided to concentrate on the power going to the PCM and the 3 wires going from the PCM to ground. I have a factory shop manual for this vehicle which has very good wiring diagrams. I have eliminated the switch and the ASD relay because all the instrument panel lights come on with the switch, except the CEL. I have installed temporary wiring from the relays to the inside of the cab so I could immediately turn the ASD and fuel pump relay on. I am thinking that there is a loose/bad connection or even a wire broken inside the insulation. My real problem is the narrow window of time to find the fault when the engine quits.
Finding all of the ground points and cleaning them up is a good idea if you haven’t done that. At this point, I wonder whether or not it might make sense to just replace the main wiring harnesses altogether.
Thanks, cigroller, I am in doing that next. One of the PCM grounds is near the left headlight. I am seriously considering adding a ground at the PCM and going directly to the negative post on the battery. I thought about a new harness, but believe it’s the circuit which “wakes up” the PCM when turned on. So far, every factory splice has been flawless. Looks like very high pressure is applied to the wires, but every individual wire that I have peeled apart from the splice has had shiny copper exposed.
A note about JTEC controlers; if the 5.0 volt feed to the engine sensors is shorted the PCM with shut down. Your scan tool will show no response and the check engine light will be off. If it comes back to life a check for fault codes will show none and “zero starts since erased”.
Power and gound should to the PCM should be verified, next measure the voltage of the 5 volt feed at the TPS (when the problem occurs). If the voltage is zero disconnect the crank position sensor, distributor pick-up, MAP and TPS one at a time while monitoring the volt meter or the check engine light for a reaction.
My guess is the crank position sensor is shorting. Manual or automatic transmission?
Thanks, Nevada, I keep a volt meter in the truck, and I’ll try that next time it quits. It’s an automatic transmission.