QuestionQUESTION: I have a 1995 Chrysler Concorde with a 3.5L and it will crank but not start. I used a multimeter to see if there was power going to the crankshaft position sensor and it only read 0.03 DCV after the key was turned on. After I checked that, I went and checked the ground to it and there is not a good ground going to it. I read in my repair manual that the ground comes from the PCM. Is there a way to test the PCM or would the PCM be the cause of the no start?
ANSWER: Hi Mark,
The orange wire should show 8v, the black/light blue is grounded at pin 4 of the pcm.
The signal wire is light blue/dark blue to pin 24 of the pcm. You need 8v on the orange wire or there will be no signal from the sensor. So check those connections.
I would try the ignition switch: "on-off-on-off-on and leave on", doing that in 5 seconds or less and then watch the flash, pause flashing of the check engine light and tell me the flash counts in order of appearance.
I doubt the issue is the PCM unless you don't have 8v on the orange wire and the wire isn't by chance shorted to ground.
Roland
---------- FOLLOW-UP ----------
QUESTION: Thank you for getting back to me. The codes I received are 12 and 55. I had to replace the battery recently which is probably why code 12 appears. I checked the voltage at the orange wire and it was only showing 0.03 DCV. Should I trace the wiring to make sure that the wires have not melted together somewhere?
ANSWER: Hi Mark,
I am surprised there isn't a code 11 or 54 which say there is not crank and cam signals respectively because without an 8v on the orange wire you will also get no sensor signals.
So yes, check what the resistance to ground is on the orange wires, with the pcm 60-pin plug removed, to be sure that the orange is showing infinite reading to ground. Besides the two rotational sensors the 8v does go to the fuel tank as part of fuel level sensor so the short could be alongthat pathway if indeed it does show 0 ohms to ground.
Roland
---------- FOLLOW-UP ----------
QUESTION: I checked the resistance between the PCM connector to ground and it showed 2.8 ohms. What should be my next step?
AnswerHi Mark,
The 2.8 ohms is too close to 0 to conclude that the orange wire is or is not shorted to ground as it stands, because the wire also goes to the fuel tank where it is in the fuel level sensor circuit. But, if you will remove the rear seat and look at the floor in the middle you will see a harness with a black 8-wire disconnect which has the orange wire. Open up the disconnect and measure the resistance to ground of the orange wire on both sides of the disconnect. If you indeed have the 60-pin plug of the pcm also unplugged then the orange wire coming into the disconnect from the front of the car should show infinite to ground (also assuming that you have the plugs at the crank and cam sensors also removed).
If you show a low ohmmage then that orange wire is shorted to ground somewhere between the pcm plug pin 7 and either the sensors or the fuel tank disconnect and you will have to look for damaged insulation.
If you show infinite ohms then plug the 60-pin back into the PCM and turn on the ignition and see if you now show 8 on the orange wires at the rotational sensors and at the fuel tank disconnect. If so, then the crank and cam sensors should then work and the engine will run. If you don't have 8V then that would suggest that the PCM has gone bad in that it no longer is supplying a 8v output necessary to run the sensors.
I hope this makes sense.
Roland
