No crank, no start.

105

Asked by Jan 02, 2017 at 08:05 AM about the 2006 Jeep Wrangler X

Question type: Maintenance & Repair

At my wits end. 2006 Wrangler, 4.0L, manual trans.  Known good battery, replaced all cables to battery and starter, inlcuding ground cables, verified good continuity with voltmeter/ohmmeter. Known good new starter. Known good relays, no blown fuses. New ignition switch.

Jumping ground to the control side of the starter motor relay will allow the vehicle to crank great, but won't start, assuming due to no instructions from the PCM to supply fire/fuel.

What else can I check before I spend $$$ on a new PCM + programming?

12 Answers

75,485

When cranking on the starter need to verify that there is power running down threw the small wire, when the key is engaged to start. The ignition switch may be bad.

1 of 1 people found this helpful.
75,485

I see a new ignition switch, is it adjustable? Never the less you need to see if power is running threw the small wire to the starter solenoid.

105

Not adjustable. Jumping ground to the control side of the starter motor relay allows it to crank when I turn the key to start, so wouldn't that rule out any problem with the ignition switch?

75,485

Yes. So you are talking the relay in a fuse box? The starter relay? I know you say it is good. Seems something is not grounded. I have seen before in my days that sometimes the starter itself is not grounded because of some four-en matter on the mounting surfaces. You would think tightening up the bolts would then make a ground circuit, but sometimes it doesn't. Try re grounding the starter, somehow the circuit is not complete.

105

Yeah, relay in the fuse box. I cleaned up the starter mounting area when I replaced it with the new one, so I know the issue isn't there either. I know the PCM supplies/controls the ground side of basically everything that the motor needs to run via the fuse box, injectors, spark, etc...so I'm confident it's a ground issue, just trying to make sure I'm not missing anything before I have to drop around $500 on a PCM, like there's not some other ground for the PCM that I'm missing or could even bypass without having to buy new.

75,485

A new PCM would have to be programmed, all spendy. I think I would try another starter relay first, just not dig-gin the PCM idea.

105

The 5 relays in the box are all the same part number, I've swapped out the horn and the ASD relays with the starter relay and nothing changes. Horn still works with the other relay, etc. The control side of the starter relay is just never getting grounded, which is controlled by the PCM. I don't know what else it could be. Probably going to end up having it towed to the nearest Jeep dealer to have them spend a couple hours to confirm my suspicion.

75,485

So for total understanding, because I have an idea, one of the contacts that is suppose to be ground when you plug in the relay is not grounding. When you plug in the relay is it out some so you can ground it? Is it possible that the wire is not making any contact at the connector in the fuse box? If you had a test light or a digital multi-meter could you test from the ground terminal to a power source? To verify that grounding point? Then check the grounding wire by pulling the fuse box to get in behind it to check? I only say because I have only ran across 1 bad PCM and it was in a Pontiac. Just trying to save you some $$$.

105

For the ground wire I ran, I tapped in a splice connector to the back side of the fuse box, so I know the connection to the fuse box is ok. From there, I ran it straight to the negative post on the battery. Doing this, the starter will crank great. I still have no signal to the injectors, verified with a DMM. I did not check to see if there was spark, but based on no injector signal, there's probably no spark either, because both are controlled through the PCM.

1 of 1 people found this helpful.
75,485

I did not know about the injectors, so yes thats what it is look to be.

105

For whatever it's worth, the problem was indeed the PCM. Pricey fix, but I got it done.

1 of 1 people found this helpful.
75,485

Thanks for letting me know. Glad you got it fixed.

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