Chrysler Repair: 93 3.3L wont start, is it the PCM?, position sensors, voyager 3

Question
QUESTION: Hi Roland,

I have a 1993 Pymouth Voyager 3.3L. I recently rebuilt the engine, and everything seemed to be OK- ran fine. (I replaced both the camshaft and crankshaft position sensors at the time of overhaul. Several years ago the PCM and fuel pump were replaced.) Recently I began to have intermittent starting problems. After some checking, I decided to replace the PCM with a refurbished one from MOPAR. After installation of the 'new' PCM, the engine does not start at all. I have checked the ASD and fuel pump relays- they are fine. The fuel pump is OK. I have checked all the wiring to the position sensors; all OK. When I turn the key to the ignition position, the fuel pump comes on briefly and then stops, as it should
do. When I crank the engine I get no voltage at pin 51 of the PCM, so the ASD and fuel pump relays do not pick up. I believe that the two aforementioned position sensors are
OK. The only codes I am getting are 12 and 55, which are nothing. I then disconnected both cam and crank sensors and cranked the engine. I rechecked the codes, and still I only see 12 and 55- no 11, as I would have expected.
Does this possibly mean a bad PCM? Shouldn't I get a code 11 with either or both position sensors unplugged?

Thanks much,
Frank


ANSWER: Hi Frank,
I would think that you should get a code 11 and or 54 with the two sensors disconnected. Did you try it for long enough to set the code? I am not sure what the threshold is for that.
On your analysis, the proper response of the PCM at pin 51 is to ground one end of the ASD relay coil as the other end of the coil always has 12V on it when the ignition switch is in the run or start position. You might try checking the dark blue wire at the ASD socket as that is the one that puts 12V on the coil. It is possible that the ignition switch is bad in that it will put power on that wire in the run position, but not the start position.
The other possibility is as you say that the PCM is bad, but I would first verify that the dark blue/yellow wire at the ASD (which is connecter to pin 51) is indeed not being GROUNDED when you are trying to start the van. You can see how it reads when you first turn the ignition switch to run, and then how it reads after 1 second when the ASD is disconnected as per design. Then see how it behaves in the start position. I am not sure whether it floats or has 12V on it to open the ASD, either one would do it. But it definitely should be grounded in the start position and while the engine is running, and for 1 second when you first turn the switch to "run" position
Lets not deal with the lack of codes yet.
Roland
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---------- FOLLOW-UP ----------

QUESTION: Hi Roland,

I see that I was looking at the wiring diagram incorrectly. Anyhow, I have +12V at the ASD dk. blue wire terminal, both when in the Ignition and Start positions. By this I assume the Ignition Switch is probably OK. I have 12V across the coil of the ASD for 1 sec after putting the Ignition SW on, then nothing. By this I assume that the PCM is grounding thru term 51 for one sec; then the ground is removed. I didn't check the voltage at the blu/yel wire terminal of the ASD (pin 51 of PCM), but assume it would have shown 0V when the ASD was energized and +12V when it wasn't. I also checked the codes again and still have only 12 and 55. I cranked the engine repeatedly (for at least 30s) with the camshaft position sensor unplugged, and still get only 12 and 55. I'll probably try to test lamp the two position sensors outputs next- wish I had a o'scope...

Thanks for your help.

Frank

Answer
Hi Frank,
OK, focus on the sensors. See if you have 9V on the orange wires, then measure voltage between the black/light blue ground and the third wire each sensor which is the signal wire while you turn the crank pulley bolt by hand. You should see the voltage oscillate between 5V and 0.3V several times per revolution (different number of times for the two sensors). That will show if you have good sensors. The final thing would be to check the wiring to the PCM plug of all the sensor wires.
Roland