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Unread 05-27-2013, 07:04 PM   #1
primo382
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2005 TJ 2.4L No Power to PCM

My compliments to the forum admins and the contributors. I could tell after reading just a few threads that this was the knowledge base I needed to track down the issue. Thank you in advance for your help.

Brief (HA!) vehicle history including diagnostic steps already taken:

Purchased the vehicle from a long time friend who bought it new in 2006. He had a brief period of stalling issues immediately followed by a no crank/no start condition. Vehicle was taken to a Chrysler dealership for diagnosis where he was told to repair a windshield leak causing a "No Bus" condition before any further diagnoses could be done ($160). Vehicle was then diagnosed by a "Automotive Wiring" shop where a diagnosis of "I was not able to find the issue but I think you need a new computer" ($250). I was able to talk him out of replacing the PCM until further diagnosis could be performed. He promptly purchased a new Jeep and this rig sat parked in his garage for over a year, When it was delivered it still had the year old tire shine from his last car wash.

I bought the vehicle with the intent of repairing, driving briefly, then selling. The asking price was too good to pass up.

I received the vehicle 3 days ago and began diagnosis. Initially I noticed no starter relay activity, no fuel pump/relay activity, no gauges (cluster indicator lights active).

Not having the correct PCM diagram (Haynes is not applicable for this vehicles PCM) I began by jumping ground to ASD and Starter relays and the starter was now working with the key but no start as fuel pump was still not running and there was no ignition spark to all 4 cylinders.

After finding the correct PCM diagram I was able to verify that the ground to the PCM was intact. Upon checking the Fused B+ line to Pin 30 (PCM Connector C1 Black) I found no voltage. I was however unable to find the source of this line in the Power Distribution Center (PDC). All fuses removed and tested with an OHM meter, all tested successfully.

Interesting note, when testing continuity from PCM Module Connector C1 Pin 30 (Fused B+) with my multimeter set to audible I initially get a "beep" for 1-2 seconds followed by a "squelch" and no sound. If I remove the leads and retest the result is the same, no matter how many times I attempt it with the connector attached to the PCM and removed.

Can anyone tell me where the line to PCM C1 Pin 30 Fused B+ is supplied from or any other components it may pass through in it's circuit? I'm beginning to feel that I am going to begin unsheathing the harness and find a failed wire but I would like to exhaust my efforts prior to this.

Thanks again for reading.

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Unread 05-28-2013, 01:50 AM   #2
Rubi4MyMrs
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The power source to C1 pin 30 is the start contacts in the ignition switch. It is not B+, it is “ignition switch output (start)” that goes to pin 30, the B+ is pin 29. That is the same wire that goes to the starter relay. That is probably why it wouldn’t engage the starter either. What did you do to get the starter relay to close & engage the starter? The wire is pink/orange & pin 6 in the ignition switch connector. The red wire at pin 1 (there are 2 red wires in that connector) supplies the power for those contacts (from fuse 22 in the PDC). That red wire also powers the cluster, radio, turn signals, fuel pump & ASD relays, & the SKIM module if you have the gray SKIM key & maybe a couple other things from the ignition switch so start there. If that red wire has power the actuator pin may be cracked or broken causing the key not to turn the switch far enough to make that contact. That pin is not dealer supplied but Dorman makes a replacement #924-704, I think. There is a u-tube video on replacing the pin & it is a somewhat common problem. You will need a security T-10 Torx bit to remove the assembly as noted in the video.

Here is a link with the video & photo of the switch & broken actuator pin.

http://www.jeepforum.com/forum/f9/ig...column-887383/
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Unread 05-28-2013, 09:55 AM   #3
primo382
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Thank you very much for the information. You are absolutely right, I was testing C1 Pin 29 B+ but reported it as Pin 30. The source of Pin 29 B+ was the correct question I should have been asking.

That is very valuable information pertaining to the ignition switch input/output and I will begin testing again after work today. In order to get the starter to engage I supplied a new ground directly to the starter relay, which allowed cranking using the ignition switch. However that was just for testing purposes after reading that the PCM supplies the ground to the starter relay.

The vehicle came with a new ignition switch that was still in the box, sitting in the center console. In speaking with the previous owner he said the ignition switch was plugged in and with the key in the run position the ignition switch was turned with a screwdriver, but no change in the condition. I replicated his test briefly when I found the switch and indeed found no change.

I will test Pin 1 at the ignition switch harness to verify 12V and voltage to Pin 6 with the key in the start position and report the results.

Thank you for your help.
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Unread 05-28-2013, 11:46 AM   #4
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OK pin 29 is the B+ red wire from fuse #9 in the PDC which also powers ASD relay (terminal 30) which is red/yellow.

Yes, the PCM grounds the starter relay coil. That happens when the clutch safety switch is closed (possibly other conditions but I don’t think so). Of course the PCM probably needs proper power for that to happen as well.


Lacking power to pin 29 makes more sense & probably eliminates the ignition switch/actuator pin as probable problem areas.
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Unread 05-28-2013, 03:07 PM   #5
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Thank you for the info. I've downloaded the FSM for my model year and the diagram shows PDC Fuse 9 as the supply for the ASD relay and C1 Pin 29 B+ at PCM. Once I unsheath the looms I should be able to see the factory splice or whether the two wires are joined at the Fuse 9 pin. From there it should be fairly easy to determine where the power terminates.
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Unread 05-28-2013, 06:47 PM   #6
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I think it looks like a double crimp at the fuse (under the PDC). Those crimps are known to be bad & the wires have a break right at the crimp. Sometimes there is corrosion too. Check there, it is easier than splitting the harness. Does the ASD have power as it should or are they both dead? You also have a connector (C-104 for the 2.4) up on the firewall area above the engine, it looks like (page 8W-97-27 in the FSM), if it’s only dead at the PCM.
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Unread 05-31-2013, 08:57 AM   #7
primo382
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After not having any free time the past few nights I made some interesting/encouraging progress last night where I was able to establish two (what I feel are) distinct issues causing my no crank/no run condition.

Issue #1
I was able to trace the line R/Y from fuse #9 in the PDC through harness behind the engine where it makes a U-turn and goes through connector C-104 (Pin 1) where it comes out solid Red and ties directly to C1 Pin 29 FUSED B(+) at the PCM. The wire has power all the way through the connector but in the last 12" of the wire it loses connectivity. A jumper wire from the latter half of connector C-104 remedied my no power condition at C1 Pin 29.

Issue #2
PCM connector C1 Pin 11 FUSED IGNITION SWITCH OUTPUT (RUN-START) also did not have voltage present. Once the jumper wire was in place at C1 Pin 29 I was able to connect power directly to C1 Pin 11 to simulate ignition switch in the run position which promptly engaged a plethora of relay coils. I was able to turn the key to the start position and the vehicle fired up after what seemed like a single rotation of the engine (after having sat for over 1 year). Of course the ignition switch was rendered useless after that point because the only way to shut the vehicle down was to remove the jumper wire to C1 Pin 11. However I was encouraged that I was able to find the issue.

My next course of action will be to determine the point in which C1 Pin 11 supply from the ignition switch terminates and that failure should be resolved. My feeling is that there will be a distinct spot within the loom that both of the wires were affected (maybe/maybe not). Since it was too dark to continue last night I will resume this evening.

I think I can rule out a faulty PCM at this point since all PCM functions seem present once power was supplied to the PCM.

But the one thing I do find odd is that to my knowledge there are only two common threads to both wires. Both are power wires for the PCM (one constant, one supplied by ignition switch) and the other is that they share the same loom. It is difficult to understand how both wires could fail simultaneously since neither can exist without the other during running condition as I tested the removal of the jumper from C104 Pin 1 to C1 Pin 29. Maybe once I open up the the loom I will have a better understanding of why this occurred.

Thanks again for all your help thus far Rubi! I feel like it's 1st and Goal on the 2 yard line and I'm very excited (especially that is has not cost me anything other than a few hours of diagnostics to this point).
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Unread 05-31-2013, 02:46 PM   #8
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Wow, that is good progress. Power to C1-11 comes from the ignition switch as you know. But if the cluster comes alive when you turn the key on then the supply power to the switch is good & power to the fuse block behind the glove box is also good (fuses 9, 10, 11, & 12). That should take you to the fuse block. Fuse 10 is for the cluster. Fuse 12 is the one that powers C1-11 as well as the ASD & FP relay coils. Make sure fuse 12 has power to it & is good. Then the pink/white wire goes to connector C301 pin 8 & on to the relays first then back to the PCM through C103. There is a 2nd wire from the fuse for the SKIM if equipped but that shouldn’t come into play here. Worth noting is that when you powered C1-11 & heard the relays closing that indicated the power was getting from the PCM back to the PDC to the relays so it seems like either fuse 12 is bad or the open point is between the fuse & the PDC (& rules out C103). Always a good place to go is the connectors & probe both sides.
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Unread 06-02-2013, 11:36 AM   #9
primo382
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Fuse 12 in the glove box fuse box was bad. Now that I think about it more than a year ago while crudely testing the ignition switch I vaguely remember sparking one of the ignition switch connector wires with the leads. This could be the possible cause of Fuse 12 being blown. Once the fused was replaced the vehicle stayed running for over an hour while driving it around the neighborhood and parked idling, until I shut it off.

I was trying to see if any of the wires became warm after an extended run-time because what peaks my interest now is still the fact that with the key in the OFF position, C1 Pin 11 IGNITION SWITCH OUTPUT (RUN-START) causes the test light to turn on with the clamp end on the Battery + Terminal and probe end on C1 Pin 11. I tried removing the ignition switch connector from the switch and testing again with the same result (lit up test light). I also tried removing connector C1 from the PCM and testing, same result. However with the key in the RUN position there is no light when performing the same test. I am curious as to what causes this circuit to be a grounding circuit with the key in the OFF position and power circuit with the key in the RUN position. I feel like I have ruled out the ignition switch and PCM with the connectors removed while testing.
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Unread 06-02-2013, 12:52 PM   #10
4banged
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If anyone knows it will be rubi4mymrs...he's helped me and many others with electrical issues...I don't even understand half of what he tells me but its always right;-)
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Unread 06-02-2013, 01:11 PM   #11
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If I understand how you are doing this you are probing the C1-11 wire with the connector off the PCM & connector off the ignition switch & getting a ground path. That is to be expected because you are probing back through that entire circuit including fuses 9, 10, 11, as well as 12. It will light the test light if anything in that circuit has a ground path (& it should). For example if any of the 3 relay coils or anything in the cluster like lights or gauges has a ground path, the test light lights. That just means there would be a normal power draw in that circuit when the key is on even if you unplug the PCM C1 connector. Not necessarily a short to ground just normal power consumption. The test light doesn't show the amperage draw, only a meter would do that to tell if there was a direct short to ground.

I think if you pull the ASD & FP relays & fuses 9, 10, &11 you will have no ground. Anyway it all sounds normal to me as long as the new fuse doesn't blow.


So other than the open wire from fuse 9 to the PCM everything is working as it should? That was the only original problem? It starts & runs with the key now with a new fuse in #12?


Thanks 4banged, I was just finishing as you posted.
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Unread 06-03-2013, 10:07 AM   #12
primo382
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Yes, everything operted normally once the broken wire to C-1 Pin 29 was repaired and Fuse 12 in the cab fuse box was replaced. They vehicle has been operating normally for over a day now. I thank you again for your help. I knew immediately after reading your first post that I was speaking to the right person regarding the issue. I have much respect for your immense knowledge.

Here is what I found when opening the harness between Connectors C-104 and PCM C-1. This was the cause of C-1 Pin 29 not having power from Fuse #9.
jeepbrokenwire1.jpg   jeepbrokenwire2.jpg  
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Unread 06-03-2013, 10:45 AM   #13
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So that wire was broken there in the middle of the wrapped harness with no other wires damaged & no sign of physical damage to the harness? That’s a bit strange it’s more likely to happen at a crimp for a terminal or at a splice.

Thank you for the kind words but you did all the work. Anyway, good job & I’m glad to see you got it fixed. Have you told your friend, the previous owner what you found?
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Unread 06-03-2013, 11:49 AM   #14
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Looks like the wire corroded from the inside out. That happens quite frequently when people probe a wire by just stabbing a test light or MM lead through the insulation and don't cover the hole when thay are done. I like to use a dab of "brush on electrical tape" to cover the hole in a wire if I am forced to probe one like that.
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Unread 07-01-2014, 12:04 PM   #15
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Bingo! This is what I'm dealing with...

In the countless threads that I've scoured, and the fixes I've attempted this feels like the right lead. My 2005 2.4l problems started intermittently (no gauges, SKIS lighton, no turn/start at all), as my old battery blew (electrode short, spilling everywhere) I replaced it and assumed that was it. Then when the problem came back, I took the cue from the SKIS light and had an expensive SentryKey spare made (had only one at that point). That _seemed_ to do the trick as I hadn't had problems since, until now...

Now the problem is 98% repeatable: no gauges, SKIS light on, no turn/start, cluster diagnostic messages buS b60 + buS b68. I have checked all fuses in the interior fuse block, a few obvious(?) & relays in the PDC. Had checked the ignition pin, and even wasted $60 on a new ignition switch. Having bought the car used, the original owner had a remote starter/alarm installed, and having ripped it out of the harness under the steering wheel I roughly inspected those taped up solder joints there.

(One, and only once in the last few weeks, did the gauges / cluster report normal on turning ignition to ON. Then when I turned it to START, ALL the power cut out, pause, a few of the needles jumped before going back to the current state.)

... I will investigate the wiring first (before finding replacement PCM, ?!), but have run into a simple problem. The electronic (PDF) format of the 2004 TJ manual I have does not seem to have the PIN outs for the latest PCM connectors. The manual has only one diagram for a 32-way / 3 row C1-C3 connectors, not matching the PINs you've described, nor the 4-row connectors that's actually on my '05 SE.

primo382, where did you find the correct wiring diagrams / connector pin-outs reference?

THANKS for documenting all of this so well guys
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