2006 Liberty - No crank, no OBD2 communication

ourobos · **Posted:** Fri Dec 16, 2022 3:54 pm

Hi, new member, was sent here from another Jeep forum for some insight into an issue I've been chasing a few weeks.

I have a 2006 Jeep Liberty Limited that just recently will not crank. Was running great, no real issues. Let me give you the long version :

I bought this for my daughter and did many things to get it road worthy, no issues other than the TPMS lights were on. My trusted local shop diagnosed it and said the WCM was not receiving signal from the TPMS and that it was a pain to replace and configure. So we let it go, I don't really care about TPMS, as I monitor tire pressure and maintain the Jeep meticulously. FWIW, the keyless entry has always worked, as well ask the SKREEM security system.

A few weeks ago, the jeep cranked 2 revolutions, then wouldn't start. It will not crank at all. The immobilizer light flashes on then off, then comes on solid. I replaced the ignition actuator pin, as that's the most common failure, with no luck. I replaced the electronic ignition as well with no luck. One oddity is that the Check Engine Light does not illuminate with key on - it did before this no start / no communication issue occurred. I had pulled codes many times. It will not illuminate key on and I feel it's in relation to the inability to pull codes. I have done MUCH troubleshooting. I can jumper the starter relay, and it cranks. I NEVER get the fuel pump on. I had jumpered the ASD relay, and it will not power the fuel pump or the starter. My initial thoughts, due to the TPMS original issue was that the WCM needed to be replaced and reprogrammed. BUT I also discovered at the time the no start happened, I also lost the ability for my simple code scanner to connect via the OBD2 port. It gets power, but says it can't communicate. I have ground at the two ground pins, but only .5v at pin 16 for battery voltage. The fuse is good, the fuse powers the OBD2 and the WCM, was really hoping that was the issue. I traced pin 16 all the way to the fuse panel, and found no breaks, continuity the whole way. This white/red wire also runs to the WCM and has 12v there, just not at the OBD2 port. I jumpered 12v from battery to pin 16 on the OBD2 but still no comm or start. Due to the OBD2 comm issue, I thought the ECU was bad. To make sure it wasn't the ECU and the WCM, I ordered an ECU from AllComputerResources, programmed to my VIN with the security disabled. I removed the WCM, plugged in the new ECU, and have the same thing - no crank and no comm at the OBD2. I am now leaning on an issue with the BCM / fuse panel or an issue somewhere in the CAN BUS connection, which I have no idea where to look for nor do I have an oscilloscope. Ground below the PCM tests good, both grounds on back of the heads test good. How can I check PCM grounding specifically on the harness, and where else does it ground? I feel there is something PCI bus related causing this.
I need help on these troubleshooting steps if possible. Any ideas are appreciated.

Thank you

WWDiesel · **Posted:** Sat Dec 17, 2022 12:17 am

This may be of help for you?
Factory Service Manuals are available for reading or downloading at:> http://www.colorado4wheel.com/manuals/Jeep/KJ/
The manuals have trouble shooting sections and full wiring diagrams.

Sounds like you have some loss of power or grounds in your system?

ourobos · **Posted:** Sat Dec 17, 2022 12:19 am

Thanks - I do have that and have the pertinent pages printed out to trace down. Still tracing wires. Any specific circuit insight is appreciated as well. Will get the probes back on it tomorrow.

ourobos · **Posted:** Thu Dec 29, 2022 9:05 pm

So, my scanner has proper 12v and ground at the OBDII port. Still won't communicate with the PCM. The MIL does not illuminate with the key on. Sentry light on solid. Tracing today, I have found the ASD relay pin 86 has 12v with the key off, if I'm reading correctly, this should only be with key on. I'd like to focus in that area, am I down to tracing this wire from the PDB? If so, any ideas on wire path and likely culprits at body edges etc?

WWDiesel · **Posted:** Fri Dec 30, 2022 2:10 am

ourobos wrote:

So, my scanner has proper 12v and ground at the OBDII port. Still won't communicate with the PCM. The MIL does not illuminate with the key on. Sentry light on solid. Tracing today, I have found the ASD relay pin 86 has 12v with the key off, if I'm reading correctly, this should only be with key on. I'd like to focus in that area, am I down to tracing this wire from the PDB? If so, any ideas on wire path and likely culprits at body edges etc?

Pin 86 & 30 on the ASD relay should test 12v+ on at all times. Power comes straight from the battery through fuse No. 6. See wiring diagram.
The ECM grounds pin 85 to energize the relay when it is satisfied with all inputs when you turn the key to the run/start position.
You could jumper pins 30 to 87 with a fused jumper to see if that powers up the ECM and network.
Security light on at all times is a problem, means the SKIM is not happy with the key chip.
Have you tried a different scanner, communication should still function unless the network is being pulled down due to a short somewhere.
You could start disconnecting each sensor one at a time while watching the scanner to see if it starts communicating with the ECM to see if one of them is pulling down the 5v network.

ourobos · **Posted:** Fri Dec 30, 2022 2:30 am

Thanks for the clarification on the circuit. I will continue diagnosing it tomorrow.

I do have a PCM I ordered to this VIN that deletes the SKREEM module, I tried it (didn't plug in the module), but same thing. I'm thinking my old PCM may be good, am working with it now with the SKREEM plugged in, if I make any progress but still have the sentry light, I will try the reprogrammed PCM without the WCM connected. Will update, thanks again.

ourobos · **Posted:** Fri Dec 30, 2022 8:23 pm

Today, I had my daughter cycle the key on while test light was hook to 12v and probing ASD socket 85. I'm reading when the key is cycled on, there should be ground there for 2-3 seconds (I'd assume to prime the fuel pump and make the immobilizer happy?). I am getting no ground here. I've checked continuity between 85 at the ASD relay socket and C3/3 (ASD Relay Control) at the PCM harness, and I have continuity there. This make me think the sentry is the culprit, and not allowing the ECU to supply ground to the ASD. Without the OBDII port communicating, I can't have a locksmith come see if it's a bad key (I only have one), or even program a brand new WCM if it's the issue. I also have a new VIN programmed PCM with sentry removed, it was no different (skreem not connected so it doesn't try to associate with it), I am going to reinstall it and see if it was a fluke. Any further ideas appreciated.

ourobos · **Posted:** Fri Dec 30, 2022 9:19 pm

I do not have B+ 12v at pin 29 C1 harness (18 gauge red) at the PCM. I am going to I am not sure where this runs from, but at every other A209 circuit I have found, I do have 12v. So my issue is my PCM isn't powering up, explains the lack of comm to the OBD2 port and inability to supply ground to the ASD. Going to trace some more, possibly supply 12v to this part of the circuit and see if I can get the ECU to wake up (requires 10v minimum, I have 0.5v).

ourobos · **Posted:** Fri Dec 30, 2022 10:10 pm

I ran a jumper wire on circuit a209 to PCM C1 #29 and it fired right up and the ECU connected. The PCM was not powering up due to this wire lacking voltage. I'm not sure where the break is, any idea where this wire runs FROM the PCM, looks like through the firewall. I'm going to monitor the battery for parasitic loss, removing the negative terminal and checking amps across it and the negative post shows no amps, so I'm hoping it was a clean break. Problem resolved hopefully.

WWDiesel · **Posted:** Sat Dec 31, 2022 12:00 am

ourobos wrote:

I ran a jumper wire on circuit a209 to PCM C1 #29 and it fired right up and the ECU connected. The PCM was not powering up due to this wire lacking voltage. I'm not sure where the break is, any idea where this wire runs FROM the PCM, looks like through the firewall. I'm going to monitor the battery for parasitic loss, removing the negative terminal and checking amps across it and the negative post shows no amps, so I'm hoping it was a clean break. Problem resolved hopefully.

I forgot yours is a gas version, my bad! :banghead:

After studying the wiring diagrams, the cavity #29 on the C1 PCM connector comes from the battery 12v. It is powered from fuse #24 (20 amp) in the Power Distribution Center (TIPM) in the engine compartment. It is an 18 gauge Red wire and goes through the C105 connector #5 pin.
Notes of interest, fuse #24 also supplies power to the fuel pump.
First I would check fuse #24 with a 12v test light to ensure you have 12v on both sides of the fuse. You cannot look at a fuse and ensure that it is good, only testing with a 12v test light or voltmeter will ensure that it is good.

If it is good, I would then pull the fuse and look at the female connectors that it plugs into and make sure there is a good tight connection on both sides with NO green crusties (corrosion).
According to the wiring diagram, the 18 ga. Red wire leaves the Power Dist. Center and runs directly to and through bulk connector C105 and then leaves there and runs directly to the PCM pin #29.

If you have power on both sides of the #24 fuse and good connection, I would probe both sides of the C105 connector pin #5 and see if 12v is present on both sides.
C105 is on the passengers side of the engine compartment according to the FSM.
I suspect your loss of power is in the C105 connector, if that is not the case, then you have a broke wire somewhere in the harness and it will be time to open up the harness and start probing the red wire every so often to locate the break.
If you need any help with the wiring diagrams, let me know. PM me your email address and I can send you wiring diagrams with the circuits highlighted.
Good luck and keep us posted.

:POPCORN:

ourobos · **Posted:** Sat Dec 31, 2022 12:28 am

Thanks much. Raining here now so can't check the fuse, but I DID check C105 on both sides and both sides have 12v. I cannot PM you due to being new, but will post my 'spam' email if you could send the wire diagrams there?

WWDiesel · **Posted:** Sat Dec 31, 2022 1:27 am

ourobos wrote:

Thanks much. Raining here now so can't check the fuse, but I DID check C105 on both sides and both sides have 12v. I cannot PM you due to being new, but will post my 'spam' email if you could send the wire diagrams there?

Fixed you "New" status, you can PM now.
I will send your an email.
FYI, you can pull up and view or download the Factory Service Manual including the wiring diagrams at:> http://www.colorado4wheel.com/manuals/Jeep/KJ/
Click on the link: 2006-KJ-SM.pdf to open the PDF, or simply download it to your computer for personal use.
If you need any help figuring out the wiring diagrams, let me know, the manual is kinda quirky, but I have years of experience with it.

So, if you have 12v on both sides of the C105 connector, then your loss of power (wire break) is between the C105 connector and the PCM.
Try piercing into the wire after the C105 and see if it has 12v. Then check it every so often in the wiring harness until you find where it has no power to find your break.
Be sure and paint the wire piercing with some liquid tape to seal up the holes to prevent any future corrosion. :wink:

2006 Liberty - No crank, no OBD2 communication

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