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Old 06-09-2019, 05:56 PM   #1 (permalink)
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Jeep TJ not starting

My '06 Jeep TJ Rubicon with manual 6spd has been giving me problems for awhile now. One day it started cutting out and stalling on the way home. It will stop doing it and run great for awhile, then start again. Sometimes just the gauge cluster goes out, other times the engine dies. I'll pull it over, shut it off for a few seconds, then restart and it runs great. Tonight it just wanted to be a total pain in the ass and run for a few seconds and die. Every time I started it. I finally gave up and called a wrecker. I've replaced the battery cable ends, the battery and the ignition switch. I've checked all wiring that includes power and ground for both the cluster and the ECM, but it all looks good.

I've come to the conclusion that it's likely the ECM. I'm working on finding one, just afraid Rubicon might run a different ECM than a regular I6 manual Wrangler. I know the Chrysler dealer will program a fresh one for me, but they're going to want way more than a pull-n-save for an ECM.

The final question I have is if maybe it might be a "Theft Locking Engine Immobilizer"-issue. Like a weak key or controller. Would a non-responding key cause the engine to only run for a few seconds?
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Old 06-09-2019, 05:59 PM   #2 (permalink)
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Cps
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Old 06-09-2019, 06:10 PM   #3 (permalink)
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Did you check the fuel filter? Fuel pump?

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Old 06-09-2019, 06:11 PM   #4 (permalink)
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that doesn't make any sense

Why would a crank sensor cause my whole gauge cluster to die while the engine continues to run fine?
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Old 06-09-2019, 06:17 PM   #5 (permalink)
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Everything you described makes me think all diagnostic work will need to be done in person while the problem is present.
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Old 06-09-2019, 06:21 PM   #6 (permalink)
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Why would a crank sensor cause my whole gauge cluster to die while the engine continues to run fine?
Everything you describe screams cps. Especially if it restarts after sitting.

When the ecm can’t read the cps it gets pissed.

If the cluster is failing, it’s probably a separate issue. When mine did that, I’d push on the cluster and it would come back to life.
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Old 06-09-2019, 06:28 PM   #7 (permalink)
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If someone could just explain if the immobilizer lets the engine run a few seconds before killing it or just won't let it hit, that could eliminate the immobilizer.

Or if someone could tell me that there's no difference between a Rubicon manual ECM and a Wrangler manual I6 ECM that could make finding one cheap much easier.

This is an intermittent problem that is killing both the cluster and the engine. That rules out fuel pump, fuel filter and crank sensor unless there's a secondary issue.

It runs awesome the rest of the time. A bad ECM would kill the cluster at the same time as it stalls the engine. A bad ground or power would kill the cluster and the engine at the same time. The engine dying and not restarting, but restarting when left off fora few seconds says ECM. I can't find a wiring problem.
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Old 06-09-2019, 06:28 PM   #8 (permalink)
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Everything you describe screams cps. Especially if it restarts after sitting.

When the ecm canít read the cps it gets pissed.

If the cluster is failing, itís probably a separate issue. When mine did that, Iíd push on the cluster and it would come back to life.
This was also my thoughts.
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Old 06-09-2019, 06:31 PM   #9 (permalink)
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Quote:
Originally Posted by Fear View Post
If someone could just explain if the immobilizer lets the engine run a few seconds before killing it or just won't let it hit, that could eliminate the immobilizer.

Or if someone could tell me that there's no difference between a Rubicon manual ECM and a Wrangler manual I6 ECM that could make finding one cheap much easier.

This is an intermittent problem that is killing both the cluster and the engine. That rules out fuel pump, fuel filter and crank sensor unless there's a secondary issue.

It runs awesome the rest of the time. A bad ECM would kill the cluster at the same time as it stalls the engine. A bad ground or power would kill the cluster and the engine at the same time. The engine dying and not restarting, but restarting when left off fora few seconds says ECM. I can't find a wiring problem.
Sounds like youíve got it figured out. Not sure why you started this thread.


Iím with beat95yj cps. If it isnít you'll have a spare for when it does go out.
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Old 06-09-2019, 06:32 PM   #10 (permalink)
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If someone could just explain if the immobilizer lets the engine run a few seconds before killing it or just won't let it hit, that could eliminate the immobilizer.

Or if someone could tell me that there's no difference between a Rubicon manual ECM and a Wrangler manual I6 ECM that could make finding one cheap much easier.

This is an intermittent problem that is killing both the cluster and the engine. That rules out fuel pump, fuel filter and crank sensor unless there's a secondary issue.

It runs awesome the rest of the time. A bad ECM would kill the cluster at the same time as it stalls the engine. A bad ground or power would kill the cluster and the engine at the same time. The engine dying and not restarting, but restarting when left off fora few seconds says ECM. I can't find a wiring problem.
You are ASSUMING that the cluster AND the engine are the same problem. On a 13 year old vehicle, it could easily be the same issue, but, it could also be two separate issues. If the engine continues to run normally with the gauges 'off', then I'd be more inclined to think bad gauges, and only after swapping in a known good cluster be willing to think bad 'source' info (ECM)
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Old 06-09-2019, 06:47 PM   #11 (permalink)
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I’m with beat95yj cps. If it isn’t you'll have a spare for when it does go out.
110% of all 4.0 engine stalling/won’t start issues are cps.

I have a tech in chit chat thread where I just went through this with my SIL’s TJ.
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Old 06-09-2019, 06:53 PM   #12 (permalink)
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https://www.pirate4x4.com/forum/gene...l-problem.html
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Old 06-11-2019, 05:26 PM   #13 (permalink)
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I had posted because I wanted answers to two questions:

1) Does the theft system disable the engine after a few seconds of running?

2) Can I swap an ECM from a non Rubicon with standard and I6 and get it to play right without reprogramming?

I just gave a little background to show context.

I'm used to looking at schematics and finding problems in electrical systems. When I'm unsure of something that can't be answered by schematics, I ask simple questions to other A-techs who might have run across information I could use a that moment.

I believe the cluster is related to the engine dying because it's an intermittent problem that might not show for weeks, but when it does, it usually includes the cluster and the engine crapping out at the same time. Just not always.

I've been an A-tech most of my life. I was just wanting answers to two simple questions.

If we must make it a dick-measuring competition, I can show copies of my factory and ASE certifications. I would be very surprised if someone here had more.

I'm not a rookie or backyard hack. I'm just wanting answers to two questions. I hear people who don't know a damn thing about me insulting me, none have even tried to answer either question.
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Old 06-12-2019, 06:55 AM   #14 (permalink)
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You're the only one turning it into a pissing match. If you know what's wrong with it, fix it. If not, listen to the folks here with lots of experience with your specific issue.
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Old 06-12-2019, 07:03 AM   #15 (permalink)
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1) Does the theft system disable the engine after a few seconds of running?
.
Google says yes;
Quote:
"this does not sound like an antitheft problem. the SKIS systems in the jeeps will allow the truck to start, but it will turn off again after 5 seconds.

FYI if your jeep key is gray, it has the SKIS system. if it is a black key, it does not.
quote stolen from interwebnet source. no personal experience

edit; since it's your own personal rig, read the owners manual. should have a nice section specifically about the operation of the anti-theft. Also, call the local jeep dealer, and ask about the ECM. they should show interchanges/part numbers per model (just an idea)
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Old 06-12-2019, 08:09 AM   #16 (permalink)
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shit, pull the codes already
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Old 06-12-2019, 10:15 AM   #17 (permalink)
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shit, pull the codes already
I realize that the OP has ruled out the CPS, but often a failing CPS will not throw a code.
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Old 06-12-2019, 10:20 AM   #18 (permalink)
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I realize that the OP has ruled out the CPS, but often a failing CPS will not throw a code.
hmm. mine did
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Old 06-12-2019, 04:37 PM   #19 (permalink)
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I've been scanning it all along with my old Genisys. I've been chasing schematics. I figured that was kind of clear. I wouldn't be at this point if I wasn't reading codes. I was just asking about the theft module to rule out a key issue (or not).

Thank you.
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Old 06-12-2019, 06:20 PM   #20 (permalink)
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I've been scanning it all along with my old Genisys. I've been chasing schematics. I figured that was kind of clear. I wouldn't be at this point if I wasn't reading codes. I was just asking about the theft module to rule out a key issue (or not).

Thank you.
Asked and answered. Is your key Grey or Black?
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Old 06-13-2019, 10:39 AM   #21 (permalink)
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Theft fuel shut off is easily read using a scan tool. It will show as "Not Allowed" or "Off". Also, there's usually a security light in the cluster that will flash. Theft fuel will not activate while you are driving the jeep, it only prevents it from starting.

AFAIK, PCMs are not different part numbers between theft and no theft, Rubicon/non Rubicon. The SKIM function in the PCM is a learned feature. Rubicon Clusters may be different, to control the lockers, Can't remember off hand.

You cannot swap PCMs, unless both are non-skim. Two SKIM equipped PCMs will not swap as the security coding will differ. Might work, though, if you also swap the matching SKIM module and matching SKIM key.

If there are no codes, and the cluster is dying while the engine stalls, Suspect that the 5 Volt reference voltage to the 3 wire sensors is shorting to ground. The PCM will shut down if the 5V reference is shorted, the number of starts since code set/erased count will be zero, too. No codes will store. The cluster on these gets most of the gauge functions through the BUS from the PCM, if it dies, no info, so the gauges die. A short in the BUS wires will also kill the gauges, engine should still run though.

Very common for the wiring harness to get chafed on the driver's side rear cylinder head stud and also near the coil connector on the passenger side of the head. Wiggle them around while the engine is running, might cause it to stall. Also, take the wrapping off the harness in those areas and inspect the wiring for damage.

Last edited by Marty, SoCal; 06-13-2019 at 10:42 AM.
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Old 06-13-2019, 11:58 AM   #22 (permalink)
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Anyone said OEM CPS yet?
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Old 06-14-2019, 03:26 PM   #23 (permalink)
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Easy to see if you have RPM signal (CPS working or not) with a scan tool or even the cheapest code readers. Cam signal, too. Might even be able to see the tach move if there is a good signal.

If you have no communications to the PCM, suspect the shorted 5V reference, too.
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Old 06-14-2019, 06:25 PM   #24 (permalink)
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Theft fuel shut off is easily read using a scan tool. It will show as "Not Allowed" or "Off". Also, there's usually a security light in the cluster that will flash. Theft fuel will not activate while you are driving the jeep, it only prevents it from starting.

AFAIK, PCMs are not different part numbers between theft and no theft, Rubicon/non Rubicon. The SKIM function in the PCM is a learned feature. Rubicon Clusters may be different, to control the lockers, Can't remember off hand.

You cannot swap PCMs, unless both are non-skim. Two SKIM equipped PCMs will not swap as the security coding will differ. Might work, though, if you also swap the matching SKIM module and matching SKIM key.

If there are no codes, and the cluster is dying while the engine stalls, Suspect that the 5 Volt reference voltage to the 3 wire sensors is shorting to ground. The PCM will shut down if the 5V reference is shorted, the number of starts since code set/erased count will be zero, too. No codes will store. The cluster on these gets most of the gauge functions through the BUS from the PCM, if it dies, no info, so the gauges die. A short in the BUS wires will also kill the gauges, engine should still run though.

Very common for the wiring harness to get chafed on the driver's side rear cylinder head stud and also near the coil connector on the passenger side of the head. Wiggle them around while the engine is running, might cause it to stall. Also, take the wrapping off the harness in those areas and inspect the wiring for damage.
^Solid tech right there^, thanks for posting. Gonna keep that one in my back pocket for the future.
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Old 06-15-2019, 07:20 AM   #25 (permalink)
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On '06 TJ's, the 5V supply wire is Pink, with a yellow tracer at the CPS connector. Black w/Dark Green is the sensor ground. Brown with the Light Blue tracer is the sensor signal to the PCM.

Testing the CPS or other 3 wire Hall Effect sensors like the cam sensor and three wire vehicle speed sensor:
If you have a digital multimeter and some sewing "T" pins, you can test the signal. Leave the connector connected. Slip the sewing pins into the connector from the harness side, along the wire so it touches the metal terminal inside the connector (Without pricking the wire insulation) Make the connection to the ground and the sensor signal wires. Crank over the engine, you should see a fluctuating voltage as the sensor makes it's output. It's putting out a square wave 0-5 Volts if you have a scope handy.

https://www.youtube.com/watch?v=QM_nVQy3-kA
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