2006 Liberty 3.7; No communication with PCM after engine replacement

[Natecroix]

Hi all, I just replaced the engine with a reman longblock in my 2006 Liberty.

Currently experiencing a no crank/no-start condition & my snap-on scan tool cannot communicate with the engine module.

No Fuel Pump Prime on Key-On
ASD relay is tested good
Starter relay is tested good

ASD relay does not click with Key-On or start


BCM codes: PCM Messages Not Received, VIN Message Not Received

SKREEM codes: PCM Status Failure

ABS codes: Lost communication with ECM/PCM; Lost Communication with TCM; Implausible data; Implausible vehicle configuration; Original VIN mismatch / Missing

I have pinned out the OBD Pin 2 to the engine harness and there is continuity.

All grounds on PCM harness are good.

PCM is receiving 12v in start/run

The starter turns when starter relay is jumped with wire

The PCM worked great before swapping the motor; it is the original PCM.

Only thing I can think of that could have caused a pcm failure is re-connecting the battery when the engine was out in order to roll up the drivers window.

Has anyone had experience with this issue and found a common problem (and hopefully solution!)

Thanks!

 

[rjkj2005]

My guess is that the engine you received is a pre 04 . They have different reluctor rings on the crank and cams. If so you will need to swap them from your old engine to the new one. This will require disassembly of the engine.
Look up Using newer 3.7 engine in older liberty. There will be a video that pops up that will explain it in detail.

Sent from my XT1585 using Tapatalk

 

[TwoBobsKJ]

My guess is that the engine you received is a pre 04 . They have different reluctor rings on the crank and cams. If so you will need to swap them from your old engine to the new one. This will require disassembly of the engine.
Look up Using newer 3.7 engine in older liberty. There will be a video that pops up that will explain it in detail.

Sent from my XT1585 using Tapatalk

But the engine would still crank - but it won't fire up and run if the timing sprocket/reluctor ring are wrong.

There's something out of whack electrically though I'm poor when it comes to electrical issues so sorry to say I'm not much help there :blah:

@Billwill is the man on here to answer the question - he's a wiz when it comes to electrical gremlins. He's in South Africa so on the other side of the clock from us North Americans but I'm sure he'll check in soon :waytogo:


Bob

 

[Natecroix]

But the engine would still crank - but it won't fire up and run if the timing sprocket/reluctor ring are wrong.

There's something out of whack electrically though I'm poor when it comes to electrical issues so sorry to say I'm not much help there :blah:

@Billwill is the man on here to answer the question - he's a wiz when it comes to electrical gremlins. He's in South Africa so on the other side of the clock from us North Americans but I'm sure he'll check in soon :waytogo:


Bob

Thanks for the responses!

I wound up finding the problem.

Battery + (B+) circuit A209 was only at 8 volts on my DVM @ pin 29 C-1 ECU connector. The factory service manual instructs to use a test light to check this pin for power, my test light lit up which was confusing... Glad I brought out the multimeter! The ECU needs at least 10v to "wake up".

I added a new fused circuit @ under hood fuse box and ran a new wire along the firewall harness to the C105 black connector near coolant resivour on passenger firewall to get solid voltage all along the A209 circuit.

ECU now gets 12.6v and it starts & works like a charm.

From the looks of it, someone had done some shoddy diagnostics on this jeep before and had left some wires exposed / not taped back up, the wire likely corroded and frayed internally when jimmying the harness around during removal / installation of the engine.

I wound up finding he FSM with all the electrical diagrams and pinouts with this fourm, thanks search feature!




The first thing I did upon receiving the replacement motor was pop the valve cover and check reluctor rings prior to starting any work whatsoever.

The old longblock looks to have had an oil pump failure, and one of the timing tensioners (passenger side) is shot. I am looking to rebuild it with this kit from rockauto:

DNJ ENGINE COMPONENTS EK1106M Engine Rebuild Kit | RockAuto

 

[TwoBobsKJ]

Great diagnostics! Glad you're up and running :waytogo:


Bob