Mechanics

NO RESPONSE FROM THE PCM

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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95sprtcpedrvr
March 14, 2012.




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.

Rivermikerat
Mar 14, 2012.
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.

Tiny
95sprtcpedrvr
Mar 14, 2012.
Check the power and ground to the PCM. Clean the contacts.

Rivermikerat
Mar 14, 2012.
I've already cleaned and checked the contacts. I have continuity to every point in the wire harness and PDC.
AD

Tiny
95sprtcpedrvr
Mar 15, 2012.
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.

Rivermikerat
Mar 15, 2012.
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."

Tiny
95sprtcpedrvr
Mar 15, 2012.
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.

Rivermikerat
Mar 15, 2012.
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.

Tiny
95sprtcpedrvr
Mar 15, 2012.
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.

Rivermikerat
Mar 16, 2012.
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.

Tiny
95sprtcpedrvr
Mar 16, 2012.

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