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No response from the PCM

Tiny
95SPRTCPEDRVR
  • MEMBER
  • 1995 DODGE NEON
  • 212 MILES
I have read into this posting; http://www.2carpros.com/questions/1995-dodge-neon-faulty-pcm

Driving along and the car dies, no CEL, tach and speedo gauge needles drop to nil and i can't hear the fuel pump running.

It turns over, NO CEL, no response from the tach and no noise from the fuel pump. I checked for voltage at the PDC for always on and key on circuits that checked out, Fuses and relays have been cleared and I initially thought it was the fuel pump and replaced that, no luck there.

I also updated the ckps, cmps and vss for the new connector style. I have ran redundant grounding at the connection points for the pcm to the (-) battery post.

There is no designated time, operating temp or driving conditions to trace what might be the problem.It just happens out of the blue and with NO warning.

Plus the PCM never shows a code.

I also checked the condition of the wires running underneath the exhaust manifold, around the egr valve and there were no signs of physical damage from heat other than the wire insulation sicking to each other.

I have a couple of videos posted here. http://forums.neons.org/viewtopic.php?f=1&t=389292&p=3275197#p3275197
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Wednesday, March 14th, 2012 AT 6:57 AM

13 Replies

Tiny
RIVERMIKERAT
  • MECHANIC
  • 6,110 POSTS
Check for spark. Check the timing belt. Make sure the fuel pump is getting power. Make sure the fuel injectors are getting power and being pulsed.
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Wednesday, March 14th, 2012 AT 7:56 AM
Tiny
95SPRTCPEDRVR
  • MEMBER
  • 7 POSTS
Timing has been checked; fuel pump, injectors and spark is there when the pcm is active and not when the pcm is shut down. Something is causing the pcm to shut down.
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Wednesday, March 14th, 2012 AT 7:48 PM
Tiny
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  • MECHANIC
  • 6,110 POSTS
Check the power and ground to the PCM. Clean the contacts.
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Wednesday, March 14th, 2012 AT 9:33 PM
Tiny
95SPRTCPEDRVR
  • MEMBER
  • 7 POSTS
I've already cleaned and checked the contacts. I have continuity to every point in the wire harness and PDC.
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Thursday, March 15th, 2012 AT 5:37 AM
Tiny
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  • MECHANIC
  • 6,110 POSTS
Check power and ground when the problem occurs. Check for power to the fuel pump and injectors, as well as injector pulsing when the problem occurs. Check fuel pressure when the problem occurs. Check for spark, when the problem is occurring.
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Thursday, March 15th, 2012 AT 5:50 AM
Tiny
95SPRTCPEDRVR
  • MEMBER
  • 7 POSTS
AS stated earlier; "Timing has been checked; fuel pump, injectors and spark is there when the pcm is active and NOT when the pcm is shut down(when the problem has occurred). Something is causing the pcm to shut down."
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Thursday, March 15th, 2012 AT 6:02 AM
Tiny
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  • MECHANIC
  • 6,110 POSTS
Do you have access to an analog voltmeter? You can check for codes. My guess (without codes) is that you're going to lose your PCM fairly soon.
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Thursday, March 15th, 2012 AT 6:49 AM
Tiny
95SPRTCPEDRVR
  • MEMBER
  • 7 POSTS
I have a digital multimeter is all and I've been trying to borrow a Fluke w/oscilloscope but no luck getting it between jobs. True the PCM is showing no codes even if I leave the battery connected after it has shut down. It eventually comes back on but there is no time limit on when it would come on. Usually I've had to wait at least overnight. You have stated my fear that the pcm is toasted, but I'm afraid what the cause might be and I don't want it to happen again if I get another pcm.
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Thursday, March 15th, 2012 AT 9:33 PM
Tiny
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It could be age. If you've ever had it jump started, that could contribute to it.

A digital meter won't work to check codes. They don't respond fast enough. The scope might work.
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Friday, March 16th, 2012 AT 2:26 AM
Tiny
95SPRTCPEDRVR
  • MEMBER
  • 7 POSTS
I'm presently in the search for a PCM now. I will take it in hopefully when I can to get it scoped unless I can get my hands on that fluke sooner. I have the profiles for the cam and crank sensors signals, do you have any other recommended signals I should check? I have an OBD reader if that what you mean by checking codes and there are no codes other than a battery disconnect within 50 cycles which is what I expected.
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Friday, March 16th, 2012 AT 4:43 PM
Tiny
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Yes, the OBD scanner works fine. You can use the digital meter to check continuity across the cam and crank sensors when hot, by manually turning the engine over. Using the start would probably be too quick for the meter to respond.
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Friday, March 16th, 2012 AT 9:17 PM
Tiny
95SPRTCPEDRVR
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  • 7 POSTS
Thank you for your input, it turns out that it was the PCM. I replaced it and problem has been solved. No problems for at least a week.
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Friday, March 30th, 2012 AT 5:27 PM
Tiny
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Glad to hear it and have been able to help.
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Saturday, March 31st, 2012 AT 7:28 PM

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