GregH Posted June 5, 2014 Share Posted June 5, 2014 I'm working on this for the local shop. Someone else put an engine in it, and it wouldn't run after that. Codes for ECT and TPS high input. PIDs show -40F ECT and 100% TPS. Unplugged sensors and grounded the signal return, I can make the signals change. VREF is holding at 5.0V Sensor ground, though (BK/LB wire) is showing 5V... I would have expected 0V. I supplied an auxillary ground on the sensor ground wire, and my sensor readings came back into line. Load test power and ground to PCM - lit a turn signal bulb just fine. The harness was in a bad way. Dirty, broken connectors, pierced wiring. I took the harness off and am cleaning it up on a table. With a restored harness, if I still read 5V on the sensor ground wire, am I looking at a failed PCM? Do these PCMs fail often? I know with Ford, if the pinpoint test leads to a PCM, I'd better go back and redo the test - it's never a bad PCM. Is it this way with Dodge? Thanks for the help! Quote Link to comment Share on other sites More sharing options...
mchan68 Posted June 5, 2014 Share Posted June 5, 2014 Just throwing my 2 cents out there, but I vaguely recall seeing someone attempt to boost start one, that fried the PCM when the polarity was accidentally reversed. There are also two small grounds, each adjacent to the headlight assembly secured to the rad support. If I recall correctly, if one of them is disconnected, the fuel pump won't run and if there is an issue with the other ground, the corresponding headlight and signal light won't work. Not sure how much if any, this helps. Can you still retrieve codes with these, by cycling the ignition between OFF and RUN three times? Quote Link to comment Share on other sites More sharing options...
8WA Sman Posted June 5, 2014 Share Posted June 5, 2014 I would start be unhooking the other 5 volt sensors one @ a time, think Ford DPFE with the metal case shorted to 5 volt ref. I would prob start with the cam & crank sensors. If you can't find any sensor issues back that terminal out of the PCM connector and recheck,it you have 5 volts on the PCM side and not the harness side, I would say bad PCM. Did you happen to notice if CEL came on in bulb check? If you end up needing a PCM let me know as I have a Mopar reman upstairs that did not fix one years ago that I would donate.(I now avoid some Mopar stuff like the plague, the Neon being @ the top of the list Quote Link to comment Share on other sites More sharing options...
Fredsvt Posted June 7, 2014 Share Posted June 7, 2014 A bad Chrysler PCM, no it can't be! Is the engine out of a 2001? Those years of Chryslers changed PCM types, as well as the way the ckp/cmp patterns read, you can't just swap in a used or reman motor. Years 2001, 2002, and 2003 and up of the 2.0 are all different. Quote Link to comment Share on other sites More sharing options...
GregH Posted June 7, 2014 Author Share Posted June 7, 2014 A bad Chrysler PCM, no it can't be! Is the engine out of a 2001? Those years of Chryslers changed PCM types, as well as the way the ckp/cmp patterns read, you can't just swap in a used or reman motor. Years 2001, 2002, and 2003 and up of the 2.0 are all different. You're right about that! I researched a bit before diving in, and found this out. Big differences in sync patterns! Quote Link to comment Share on other sites More sharing options...
GregH Posted June 12, 2014 Author Share Posted June 12, 2014 Ok, went through the wiring harness, found a few faults and fixed those. Reconnected to the PCM, and found no ground present on the sensor ground wire. Supplied a ground on that circuit, and all my sensors came back and read properly. My automatic shutdown relay turns on for one second when I turn on the key, then turns off. It supplies power to injectors and coil for that one second, then cuts the power. During cranking, the shutdown relay remains off - so the engine will not even try to start. I jumped the coil side to ground to force the relay on, and the engine still will not start with power to the injectors and coil. Check the ground signals from the PCM to the injectors and coil. The PCM is not triggering the injectors or coil. So, my question, if the PCM cannot read engine speed or sync on the engine, from a faulty CKP, CMP, or a wrong year model engine, will the PCM keep the automatic shutdown relay open? Does the PCM wait to turn on power to the injectors and coil until it sees the engine cranking? Thanks for the help! Quote Link to comment Share on other sites More sharing options...
8WA Sman Posted June 12, 2014 Share Posted June 12, 2014 Are you able to see the ASD relay, ignition sense, sync & maybe another 12 volt pid on the scan tool. SI states....The sensor return circuit provides a low electrical noise ground reference for all of the systems sensors. The sensor return circuit connects to internal ground circuits within the PCM . If you have no low Ref and all powers and grounds to PCM are good, I would load test them....Then I call bad PCM :hammer: Quote Link to comment Share on other sites More sharing options...
Bruce Amacker Posted June 12, 2014 Share Posted June 12, 2014 So, my question, if the PCM cannot read engine speed or sync on the engine, from a faulty CKP, CMP, or a wrong year model engine, will the PCM keep the automatic shutdown relay open? Does the PCM wait to turn on power to the injectors and coil until it sees the engine cranking? From what I remember, yes. The ASD closes for a few seconds at KOEO and then opens, it does not close again until the PCM sees a crank signal from the CKP. I'm thinking bad PCM also. Good Luck! Quote Link to comment Share on other sites More sharing options...
sneakypete Posted June 14, 2014 Share Posted June 14, 2014 Bruce is right. The pcm won't ground the ASD relay until it sees a valid crank signal. Quote Link to comment Share on other sites More sharing options...
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