02 Liberty at wits end

[Macdaddy]

Any help out there would be appreciated...My Liberty will start and run for a couple minutes, then die...lost ac compressor bearing prior to this, after replacing compressor, had problem...getting code 1391 for intermittent loss of cps signal...replaced sensor (genuine mopar), cam sensor (mopar)...checked wiring, connector plug, still won't run...after dying hard to start acts out of time...after sits for hour or more will start again and idles fine for few minutes til dying and acting out of time...possibly thinking I have damage to chain or chains, or tensioners...or broke key on sprocket somewhere in timing ...has 128,000 miles...any ideas?

 

[ltd02]

I'm not much of a help but still sounds like a sensor issue or wiring. I'd have to say that if it were really out of time due to damaged jumped chain or crank keyway it would never idle fine even briefly.

 

[Macdaddy]

I'm hoping so...I just can't seem to find anything else wrong with wiring or connectors...I can clear code, then reappears with engine light. First thought had some thermal problem with wiring but can't find any melted or damaged wire.very strange deal...pretty nice jeep been sitting for 5 mo. I even replaced cpu and tps...

 

[Billwill]

You will need to trace the wiring for the CPS sensor in greater detail...the wiring for the KJs tends to go all around the engine bay....does not take the shortest route point to point!

This means that the leads for the CPS sensor will go through several connectors and several places where the insulation wears down and the copper touches chassis occasionally.

First disconnect the battery and check the connectors on the PCM...re-plug the connectors a few times to clean the contacts off.

Then go through the wiring diagrams to see where the relevant wires goes through connectors and re-plug those connectors. The wiring diagrams have a section that shows where the connectors are located.

Worse case scenario is that you need to unplug the sensor and the corresponding PCM connector and then with a digital multi meter set to Ohms trace each wiring for continuity from point to point while shaking the connectors and harness around to see if you lose contact. Also with both ends of the wire disconnected check for leakage to chassis with your meter as you shake the wiring around....should be infinite resistance!

The trouble with the wiring is that it usually becomes part of a thick harness with other wires and somewhere along the way your relevant wires could rub through onto other random wires....I had about 7 occurances of this happening on my 2002 Export CRD after a front end collision caused damage to the harness under the radiator. The only way to fix these problems was to cut off both ends of the suspect wire...including cutting off any splices....so that the wiring was completely isolated. Then I would replace the wiring with new sections while taking the shortest point to point route.

If you do not have the 2002 KJ Wiring diagrams download the 2002 KJ Service Manual here...I will have a look through them as well.

Service manuals: Index of /manuals/Jeep/KJ

Update: Having a quick look at page 8Wa-30-9 of the 2002 KJ Service Manual...the Camshaft Position Sensor has a Tan/Yellow wire going from pin 3 of the CPS sensor through to pin 18 of Connector C1 on the PCM. This wire goes via connector C110...use the Connector Location section to find this connector C110 and re-plug it.

C101 supplies ground to this sensor via a Black/Light Blue wire but this also supplies the Crankshaft Position Sensor so if this was faulty you should expect CEL codes for this sensor as well.

Unfortunately lots of splices in the circuitry but these are common once again to the Crank sensor so unlikely the fault is in this area.

With battery disconnected and Cam Sensor unplugged and PCM connector C1 unplugged the Tan/Yellow wire should show good connectivity end to end and no leakage to chassis/engine. If this is not the case then you need to cut both ends of this Tan/Yellow wire off and replace it with a new wire going direct from the Cam sensor to the PCM connector C1 pin 18 position.

 

[JasonJ]

^ That ought to do it.

Bill, as always providing accurate and excellent diagnostic information.

 

[Macdaddy]

Thank u very much...sounds like good plan...it is all such a strange deal being good for a minute or two then, act up...appreciate your input ,will get started with diagrams...and start looking

 

[JasonJ]

Thank u very much...sounds like good plan...it is all such a strange deal being good for a minute or two then, act up...appreciate your input ,will get started with diagrams...and start looking

Might be worth borrowing one, or finding a friend with one, but a diagnostic scantool that can show live sensor readouts would be helpful to see what and where the signals are going awry.

I bought an Innova 3160d on Amazon for about $160.. I bought it to scan ABS and SRS codes, but it does live sensor and freeze frame data as well. That would indicate what sensor is throwing the goofy signal and/or what circuit you at least need to focus on.

 

[Billwill]

Yep a good scan tool would be a great help to check which sensor is really causing the problem.

Unfortunately for me here in SA the 2002 Export CRD Bosch ECM cannot even be read by the local Bosch Agents....have to take it to the Dealers and they are pretty useless so I have taught myself pretty well as regards electrical fault finding on my Jeep!

The PCI bus on these early KJs are also difficult to read with most scanners available here.

 

[Macdaddy]

Thanks for the input!! Helps me try to figure this weird mess out!

 

[tjkj2002]

Might be worth borrowing one, or finding a friend with one, but a diagnostic scantool that can show live sensor readouts would be helpful to see what and where the signals are going awry.

I bought an Innova 3160d on Amazon for about $160.. I bought it to scan ABS and SRS codes, but it does live sensor and freeze frame data as well. That would indicate what sensor is throwing the goofy signal and/or what circuit you at least need to focus on.

Very basic code puller and not a scan tool,there is a difference and a huge on at that trying to compare that to a actual scan tool.

 

[JasonJ]

Very basic code puller and not a scan tool,there is a difference and a huge on at that trying to compare that to a actual scan tool.

Oh for sure, big difference between diagnostic tools costing thousands and everything else.

I'd hesitate to classify what I have as a "very basic code puller", as it does much more than just display DTC's. Certainly in no league with the pro tools from Snap-On, or what is equipped in a dealer garage.

 

[Macdaddy]

Well ...spent another day on the ol Liberty...bypassed the loom on the gry w/blk wire for crank sensor and the tan w/ylw wire for cam sensor on pins #8 and #18 respectively. ..spliced in at plugs as far as possible to eliminated all wire....still no help....I have found I can kill engine most times by shaking wiring behind motor and toward computer..but can't seem to zero in on it...I guess my next move is to bypass the ground side on each sensor and see if there is a bad section...it really seems to be thermal problem as it will restart and run for awhile every time it cools some...pulled most of my hair out...but still looking...thanks for the advice I think I might be on right track...