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Chrysler Repair/1994 LHS: no start no spark, no 8V


QUESTION: im down to pcm pin 7 that is not out putting power to crank and cam shaft sensor.  i have good continuity from pcm to wire harness on both.

how can i test power going into pcm and grounds on pcm so i know if it needs to be replaced or if its a connection causing issue.

ANSWER: Hi Russell,
The power to the pcm is 12V on pin 3 direct from the battery, and the pcm is grounded at pins 5,11,12 of the plug. Other than disconnecting the plugs at the sensors, if this is a flex fuel engine then that would be the only other item which utilizes the 8 volt supply wire and that could be shorting out the voltage. Check that the wire on pin 7 of the plug is not grounded after unplugging the sensors. The 8v is generated internally by the pcm.

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QUESTION: Thanks for the respose

This is not a flex fuel auto.

I have power at pins 3 and 9.

Can i use test light attached to pos on battery to check grounds on 5 11 12 as well as pin 7 for any grounds as well?

If all is well can i conclude that pcm is not internally out putting 8 volts to pin and need to be replaced?


ANSWER: Hi Russell,
Yes testing 5,11,12 that way should show them to be grounded and then check 7 the same way but have the plugs disconnected at the two sensors so as to check those wires are NOT grounded.
By the way, have you done a fault code readout using the ignition switch: "on-off-on-off-on and leave on" doing that in 5 seconds or less. Then watch the check engine light to see it begin to flash, pause, flash, etc. Count the number of flashes before each pause. Then repeat to be sure of an accurate set of flash counts. Let me know what you learn.

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QUESTION: Flash codes none I've disconnected battery so many times pretty sure pcm has been reset or its not sending any signal.

With pcm harness unplugged and plugged I got test light to light on 5 11 and 12.  This was with test clamp on positive of battery and tip of probe touching back probe on each wire to harness.

With pcm harness unplugged and both cam and crank sensors unplugged no light and good continuity checked with dmm.


Aloha from hawaii

Hi Russell,
With no 8v on pin 7 and the wires connected to that pin not being shorted to ground, and with verified 12v on pins 3 and 9, and grounded on pins 5,11,12 it would appear to indicate that the pcm has failed. Also no 'check engine' light function corroborates. Next step would be to find a used pcm that was installed on a '94 LX-body car with the same size (L) engine.

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Roland Finston


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