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General discussion

96 Jeep Cherokee With 4L

Mar 16, 2008 9:32AM PDT

What causes the ECM to have and intermittent connection to the ignition. It is not the wires pluged in to the ECM. When you push on the ECM the connection stays connected and is not intermittent.

Discussion is locked

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Ignition failures
Mar 16, 2008 8:58PM PDT

What causes the ECM/PCM (same part) to have and intermittent connection to the ignition??? Check/replace ASD relay and F8 fuse in enging fuse box and verify door security system is working.
Cat5

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Note Askywards responded to me and I'm sending on to you.
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It's the PCM
by askyward - 3/15/08 3:56 PM

Let me put the bottom line first: Its the PCM.

Now for the long story.
Regarding Ignition Coil Driver Fault P0351:
An ignition coil driver is the signal that comes OUT (key word "out") of your PCM at pin A7. The "A" plug is the Black plug nearest your engine that goes into the PCM. So, Pin A7 tells your coil what to do. So it can't be the coil... its the command "to" the coil originating inside the PCM.

Guess what goes "in" at pin A8? The input signal from your crankshaft sensor. And just above it is pin A18 the camshaft sensor input. These inputs are critical so its no suprize that everyone is running around replacing them even though they don't solve the problem. Anyway, one more item before I deliver the punchline.

The main symptom we all have is that the car dies (DTC P0351). Another problem is very low idle; at a stop sign for instance. Trying to make it home by gunning the throttle while riding the brake. Sound familier?? Guess what signal comes out of pin A10, A11, A19, A20? The Idle Air Control signal to the Idle Air Control Valve that is bolted to your throttle body. (Of the 3 sensors on the TB, its the one closest to the valve cover and it controls the idle of your engine).

All of these pins reside together in an area about 1/4" square.

Punchline/Bottom Line: I strongly believe that... The circuit board behind these pins is faulty, either totally or intermitantly.

Is it any wonder that the miracle TORX screw fix that started this blog is indeed a miracle??? That screw is less than an inch from these group of pins...it is either eleviating or illiminating the short/fault.

I urge you all to go to jeepforum.com and start at post 31.
http://www.jeepforum.com/forum/showthread.php?t=522719&page=3

I re-read a few key paragraphs in the Jeep Haynes Repair Manual (that green book #50025) and it was like duh... stop throwing money at things and go back to basics... there are inputs to the PCM, and there are signals out of the PCM (page 6-5). Read Page 5-5, middle of the page "All Models". The rest of Chp 5 and 6 on checking engine sensors was an easy guide to confirm that the 5 volt DC power, and the ground connecting the sensors to the PCM were good. And finally the Wiring diagrams that start on page 12-40 (1 thru 6).

I share your pain in this, and so I share my conclusions of trying to take the mystery out of sensors, TORX screws, and DRB codes.

Good luck, d
1996 JGCL. 4.0L, I6, Auto, 4x4, 185,000 miles. All new sensors. rebuilt engine 1 year ago, E22 recall Nov 07... PCM pain Dec 07.

PS: This post is pretty much at the microscopic level, but if you have DTC # P0351, I would tend to agree that you need a new PCM. How to get a PCM and the pain that will bring is stated better at the jeepforum link posted above.

PSS: I still am paranoid and cynical enough to believe that Jeep Recall E22, that reprogramed the PCM to detect a Catalytic Converter failure is part of this problem, and that is for another day. So I extoll my short circuit theory unable to prove a programming/software glitch like we see on our PCs all the time. Anyone else out there have this PCM pain shortly after going to the dealer for E22 and a free/refund on your CAT????

Post 159 of 160 of......... Jeep Fixed

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Ok... But?
Mar 17, 2008 6:28AM PDT

I Know its the ECM internaly but is there anything that causes this to fail so I don't fry the new ECM.

Thanks Much!

- Trip -

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response
Mar 17, 2008 11:58AM PDT

Timer150... I'm not a mechanic... read and ask Askyward above... His post was #159 of 160 when that was written on the other forum Ignitions, I think?... Reply to him and ask...ok.

To remind you that to disconnect the battery any time you are replacing PCM/ECM, Relays, Fuses... anything electrical. if you have not done so to read all posts and take notes!!!

Good luck!