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2005 TJ died and now it won't start


2005LJU

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2005 LJ 79K miles, 42RLE auto. Today was driving down a dirt road and the jeep just died..stopped running. Now I have a no start/no crank issue. Electrical power is good to everything else. Lights, dash, radio, winch (had to winch it on the trailer).

Here's what I know so far:

It Will now not communicate/connect with my scan gauge at the OBD2 port.
I tried cycling the shift lever and trying to start it at the same time to see if it was some type of safety switch lockout issue.
When I turn the ignition to ON, I don't hear the fuel pump running/priming like it should before the start.
Under normal operation the CEL light will come on briefly before engine start when the key is placed in the ON position. Now, when key is turned to the on position, the CEL will not illuminate.

Am I looking at a dead ECM/PCM? ..or are there some other things that I should be looking at. I've checked all connections/fuses/etc. Truly at a loss right now and would like to get some input before I start shotgunning parts on it.

Thank you...
 
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2005LJU

2005LJU

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I failed to mention that there was no CEL/no codes/no pending codes before this occurred. I live in an emissions testing area and just recently passed a successful test. I also just performed Service Bulletin 25-003-13 for the wiring fix the readiness issue prior to emissions testing.
 
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ItchyDong

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Being that the fuel pump/no crank/dying issue showed up at the same time, I'd suspect something fruity with either your ignition switch or your ASD relay if all of your fuses are good.
 
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2005LJU

2005LJU

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Being that the fuel pump/no crank/dying issue showed up at the same time, I'd suspect something fruity with either your ignition switch or your ASD relay if all of your fuses are good.

It all happened at once while driving. All fuses are good. Have not been able to check power/ground at ECU yet.
 
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In my experience working on Toyotas for over 30 years. If you have power and ground at ECU and no CEL. I would start looking at the ECU itself. There may be other things that are common to Jeeps that I am not aware of. I am new to Jeeps. Bought my first on earlier this year.
 
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CharlesHS

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Remove the four 32 pin harness connectors from the ECU and check for oxidation on the pins and clips; firmly snap the connectors back into the ECU receptacles. Has communications been restored ?
Check the voltage at the battery terminals; then check the cable clamps and battery terminals for oxidation and ensure the clamps a snugged onto the battery terminals. IF the battery has the proper voltage 12.5+ and the cables going to the PDC (fuse block) are tight; then there is a good chance your ECU is fried. IF there isn't at least 12.0; then the question is WHY ? Alternator or ECU ?
Contact @Wranglerfix who is the resident ECU repair technician...
 
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2005LJU

2005LJU

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Remove the four 32 pin harness connectors from the ECU and check for oxidation on the pins and clips; firmly snap the connectors back into the ECU receptacles. Has communications been restored ?
Check the voltage at the battery terminals; then check the cable clamps and battery terminals for oxidation and ensure the clamps a snugged onto the battery terminals. IF the battery has the proper voltage 12.5+ and the cables going to the PDC (fuse block) are tight; then there is a good chance your ECU is fried. IF there isn't at least 12.0; then the question is WHY ? Alternator or ECU ?
Contact @Wranglerfix who is the resident ECU repair technician...
I did all the above today. Batt voltage checked good, cleaned terminals/connectors, checked/cleaned grounds, removed and inspected all four 32 pin harness connectors and reseated. Also checked wiring harness as best I could. Also completely Disconnected the only aftermarket electrical item which is the winch. Still no luck. Tried to test for power going to the ECU but I'm not sure I was doing it correctly.

I reached out to @Wranglerfix today. Said I could send him my ECU for a test. That"s probably going to be my next step.
 
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2005LJU

2005LJU

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Update:

Still trying to troubleshoot this headache. Been testing for power in the 32 pin connectors at the ECU. I'm getting 5v power at the ORANGE C2 plug (female end) but I don't seem to be getting 5V power at the BLACK C1 plug, pin 27 (female). I do believe that I have a good ground at the C1 plug however.

I'm really still at a loss for this. Any suggestions before I start ripping into the wiring harness? Could a faulty relay be causing this?

Any suggestions are appreciated.
 

ItchyDong

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You're testing for 5 volts with the connector unplugged from the PCM? Just go pull the plug off of any number of sensors (TPS, MAF, Speed Sensor, Cam, Crank, etc.) and see if 5 volts is present. That'll tell you if the PCM is providing 5V.
 
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2005LJU

2005LJU

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There one pin labeled 5V supply in the black C1 plug and orange C2 plug. I was getting 5V at the pin in the orange plug but nothing at the pin in the Black C1 plug. i.e. power going into the PCM
 

ItchyDong

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The PCM doesn't receive 5 volts. It takes in battery voltage and turns it into 5 volts to supply the sensors with a supply voltage. Then the sensor manipulates the voltage and sends it back to the PCM for interpretation via a signal wire. Unplugging the connectors at the PCM and stabbing the female pin is not how you check for 5 volt supply. Check for 5 volts at the Crankshaft position sensor and the TPS. That'll cover both PCM supply sources.
 

Jodh

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I had the same issue and mine turned out to be the main wire harness connector in theiddle along the firewall. The tabs holding it together broke and it seperated just enough to lose connection. I found it by chance and zip tied it back together.
 
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2005LJU

2005LJU

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The PCM doesn't receive 5 volts. It takes in battery voltage and turns it into 5 volts to supply the sensors with a supply voltage. Then the sensor manipulates the voltage and sends it back to the PCM for interpretation via a signal wire. Unplugging the connectors at the PCM and stabbing the female pin is not how you check for 5 volt supply. Check for 5 volts at the Crankshaft position sensor and the TPS. That'll cover both PCM supply sources.
Thank you for the clarification. I'll continue troubleshooting.
 
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2005LJU

2005LJU

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The PCM doesn't receive 5 volts. It takes in battery voltage and turns it into 5 volts to supply the sensors with a supply voltage. Then the sensor manipulates the voltage and sends it back to the PCM for interpretation via a signal wire. Unplugging the connectors at the PCM and stabbing the female pin is not how you check for 5 volt supply. Check for 5 volts at the Crankshaft position sensor and the TPS. That'll cover both PCM supply sources.
How can you check battery voltage going into the PCM?
 

ItchyDong

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How can you check battery voltage going into the PCM?
Listen. Plug those connectors back in. Test for 5 volts at the Crankshaft sensor and the TPS. If you have 5 volts there, then you have 12 volts feeding the PCM. Can't have one without the other.

Did you ever swap your ASD relay?
 
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2005LJU

2005LJU

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Still unable to pinpoint this issue. I installed a new ECM from wranglerfix with no change. No crank/no start, no fuel pump prime, no fuel gauge or voltmeter. I have power to the lights and accessories as well. I'm not seeing 5V power at TPS, CPS, or MAP sensors.
Did a tremendous amount of troubleshooting with the help of another member on the forum. Still coming up short.

Battery is good..powers and grounds have been checked. No apparent damage to the wiring harness that I can see anywhere.


I'm curious about SKIM issues. my build sheet does not list SKIM on the build and I have black keys. However there is a 10A fuse in the spot labeled SKIM in the fuse block behind the glovebox. I also haven't seen a skim light on the cluster.

I'm truly at a loss with this issue right now.
 
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You say you have no 5v referance at the various sensors which require this voltage to operate. I've seen on Toyota's that one of the components that receive the 5v power can short internally causing no referance voltage. You might try unplugging the components one at a time and if this is the problem when you unplug the shorted component the 5v referance voltage will return. I hope this helps. I know your frustration as have dealt with similar issues over the years.
 
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