2003 Jeep TJ 4.0 will not turn over

Bane

New Member
Joined
Apr 3, 2020
Messages
20
Location
Texas
I know, I know, I know. There's a million of these but I'm stumped man.

One day I fire up my Jeep to go to Church, ease out of the driveway, and it dies in the street. Push it back in the driveway. Gauge cluster says wrong key, no fuel (I know it had gas in it), gas gauge and batt gauge don't read, gauges don't flicker or react in any way to movements of the key or attempts to start it. Actuator pin and all the physical ignition switch stuff is good, so I presume SKIM module. Send my PCM off to get the SKIM deleted, unplug my SKIM module from the ignition system under the column and discard of it, just like the company I sent it to said to. Get my PCM back, giddy as a little boy in Legoland, reinstall, still nothing. I'm super bummed, and ignore it for a while, opting to focus on other projects.

I've come back to it recently. I have since pulled the SKIM fuse in the glove box fuse block, which I either overlooked on the company website or was not told to do, and NOW, it clicks when I turn the key to start and the gauges flicker for a moment, but still nothing. But it did perhaps seem to help. DOES NOT TURN. It also seems to have developed a mysterious battery drain while it sat, which irritates me. I've replaced every fuse in the fuse block under the hood and a few in the glove box for good measure. I've tested the Crank Position sensor and the Cam Position sensor, but am paranoid that perhaps I did it wrong? I seemed to get a different readings everytime and every guide on how to check them that I see says something slightly different. Some people say that a bad CPS will only cause a no-start condition and won't even cause a no-crank condition so I don't even know if it's a possible cause. Radio and in car lights come on. Turn signals and headlights work just fine and dandy. And now the speedo and tach "jump" sometimes when I turn it to crank and get the single click, but the gas and volt gauges still are absolutely dormant. Note that I have been hooking the Jeep up to a big ol' battery charger on a 10-40 amp charge when I'm testing, and a 200 amp charge when attempting to start, so even if it's a bad battery I believe it should still work under these conditions. Could a bad battery still be possible? I have two keys for it, one that I use frequently and one that I barely use and when it initially died in the street that one lovely Sunday morning the first thing I did was try the other one and have since then been alternating between both in my tests, so the keys themselves are not to blame on either a transponder nor mechanical level.

Also my one question about testing the crank and cam sensors, when using a multimeter: which lead goes to which post inside them? I have an '03 so the Crank Position sensor is the flat layout, "A B C" style connnector as opposed to the older round " B " style connector (that "ABC" explanation probably won't make sense if you're on a phone).
A C

Does the pos or neg lead from the multimeter go to the B or C post? Should I incorporate the A post? Should I be looking for infinite or finite resistance as a sign of a faulty or functional sensor? Is it even worth my time testing the Cam sensor with these symptoms? Is my PCM flatout trashed? I don't even know if any of these things would cause a failure of just the two little gas and batt gauges.

Also, if you're going to explain the multimeter testing question to me (or likely any of this for that matter), explain it to me like I'm a complete moron, because the moment computers and sensors enter the equation I turn into one. I can rebuild a Holley in an hour, but I can't for the life of me figure out this PCM stuff. All the oldheads don't know what to do with me because I'm an energetic whippersnapper who can't comprehend technology any newer than a decade before I was born. I have been using my multimeter varying between 2k and 20k ohms so I think at least I'm doing that part right.

Thanks fellas. This Jeep was my daily for years on end and I'm going stir crazy having to drive automatics everywhere.
 
Check the battery cables for corrosion and check the grounds. It could also be a bad battery, but probably not likely with the 200 A boost.

Have you verified the ignition switch is working correctly? It sounds like it's at least working for ACC since the radio works.

You can pull up the FSM for your year under Resources on this forum.

Also, have you checked the clutch safety switch? You can bypass it with a fuse as well.
 
Also my one question about testing the crank and cam sensors, when using a multimeter: which lead goes to which post inside them? I have an '03 so the Crank Position sensor is the flat layout, "A B C" style connnector as opposed to the older round " B " style connector (that "ABC" explanation probably won't make sense if you're on a phone).
A C

Does the pos or neg lead from the multimeter go to the B or C post? Should I incorporate the A post? Should I be looking for infinite or finite resistance as a sign of a faulty or functional sensor? Is it even worth my time testing the Cam sensor with these symptoms? Is my PCM flatout trashed? I don't even know if any of these things would cause a failure of just the two little gas and batt gauges.

Also, if you're going to explain the multimeter testing question to me (or likely any of this for that matter), explain it to me like I'm a complete moron, because the moment computers and sensors enter the equation I turn into one. I can rebuild a Holley in an hour, but I can't for the life of me figure out this PCM stuff. All the oldheads don't know what to do with me because I'm an energetic whippersnapper who can't comprehend technology any newer than a decade before I was born. I have been using my multimeter varying between 2k and 20k ohms so I think at least I'm doing that part right.

Thanks fellas. This Jeep was my daily for years on end and I'm going stir crazy having to drive automatics everywhere.

You're in luck, I've been documenting a bunch of this sort of stuff to aid in troubleshooting sensor problems. For your 2003 the connector looks like this, remembering that this is the connector on the harness, not the connector at the sensor. You'll have to exercise your spatial reasoning to make sure you've got the correct pin or cavity depending on which piece of the connector you're looking at.


Camshaft position sensor tests:
https://wranglertjforum.com/threads/how-to-test-your-camshaft-position-sensor.68487/

Those same tests work for the crank position sensor, but since you have a 2003 you have the extra challenge of the wiring & connector being different depending on your engine/trans combo.

QULJ5ptehqR9Iedjih-qbcLHkJcNNDMPbvFe0EMcK1j_umV6WQ.png


Utl4RTuv2dmKjUId-BJ7FM3iU99ysC5LAwZJyI4AyO8nZ4wcQw.png



I know you said to explain like you're a complete moron... I think I wrote them pretty simple to understand but what's simple for one person is complicated for another. While I'm typing this I'm listening to a youtube on the Raft Consensus Algorithm, which is pretty complex. I'm happy to explain any of the testing process that doesn't make sense.
 
You're in luck, I've been documenting a bunch of this sort of stuff to aid in troubleshooting sensor problems. For your 2003 the connector looks like this, remembering that this is the connector on the harness, not the connector at the sensor. You'll have to exercise your spatial reasoning to make sure you've got the correct pin or cavity depending on which piece of the connector you're looking at.


Camshaft position sensor tests:
https://wranglertjforum.com/threads/how-to-test-your-camshaft-position-sensor.68487/

Those same tests work for the crank position sensor, but since you have a 2003 you have the extra challenge of the wiring & connector being different depending on your engine/trans combo.

View attachment 405906

View attachment 405907


I know you said to explain like you're a complete moron... I think I wrote them pretty simple to understand but what's simple for one person is complicated for another. While I'm typing this I'm listening to a youtube on the Raft Consensus Algorithm, which is pretty complex. I'm happy to explain any of the testing process that doesn't make sense.

Awesome, man. Up until now I've only heard different takes on which multimeter lead goes to which cavity, but haven't actually been told which cavity serves which purpose. I've got a 4.0 standard so that's no biggie.

And just to make sure, I should use a 5V power supply to test the sensor itself, and use the battery with the key on to test continuity between the harness-side and the PCM connection? In the video he uses a screwdriver to interrupt the magnet in the cam sensor to see if it reads. How should I replicate this with the crank sensor?

With any luck, I'll find that one or both of my sensors is trashed and I don't have to drop 1,200 Hopes and Dreams on a new PCM.
 
Check the battery cables for corrosion and check the grounds. It could also be a bad battery, but probably not likely with the 200 A boost.

Have you verified the ignition switch is working correctly? It sounds like it's at least working for ACC since the radio works.

You can pull up the FSM for your year under Resources on this forum.

Also, have you checked the clutch safety switch? You can bypass it with a fuse as well.

I can't find any reason to suspect the ignition switch and the clicking hen I turn it to start suggests to me that it is communicating with the starter, I believe.

I have already bypassed the clutch safety.

I'll check battery for the heck of it.
 
Alright I got an update for y'all with some new information.

The good news: Things are happening.

The bad news: The things that are happening.

So after fidgeting with some stuff I went to try to start it and it gave me rapid clicks instead of a single one, which I know in Jeeps is a starter/power to starter issue. So I cleaned the battery terminals (again) and whacked the starter with a rubber mallet. Back to single click.

So I decide to test the starter out. This is where it gets weird.

You can do a very basic test to determine battery/starter integrity by turning on the headlights and attempting to start to check if they dim.

And the headlights won't turn on.

But the running lights (indicators) DO come on.

Weird, but for the sake of the test I choose to ignore it, so I'll just switch on the brights to see them.

When I pull back the turn signal stalk to flash the brights they come on just fine, but when I pull it back further to click on the high beams, they don't stay on.

Did the test manually holding the brights on and the lights did flicker when turning the key.

So now, even with the headlights on, the high beam switch acts as if they're off, but the running lights still come on. (with headlights off, the high beam switch doesn't do anything except flash the brights and hold the high beam setting for when you do turn the headlights on. Not sure if those controls work different on older TJs). And in the position when the headlight switch only turns on the indicators, it doesn't turn them on until I turn it to the headlight position, and than one click back to the indicator position. And if I turn the headlight switch all the way off, it repeats that.

All the in car controls have gone totally wackadoo and I'm at a freakin loss y'all. This really is starting to smell of a massive computer failure as far as I can tell.

What sucks even more is for computers from somewhere like Wranglerfix, which I've heard good things about so far, their ECMs aren't compatible with tuners or superchargers (which sucks because I hope to have a blown 4.6 stroker in this rig eventually).

And it's a pricey fix.

And my tests were rudimentary (I don't have a good 5V power source for testing atm. One's coming in tomorrow) but from just continuity tests with a multimeter, the results make no sense. When I connect the leads to the posts with alligator clips, sometimes it reads infinite, and sometimes it reads finite, but the numbers flash across the digital screen so fast it's hard to read them, and they're wildly inconsistent.

I'm lost fellas.


OKAY WELP

I went outside to verify something before posting this and in a "why not" sort of moment stuck my battery charger to 200 again and it cranked, but still no start. And still no gauges and still funky controls.

I'm gonna let the battery charge more I guess, but at this point the cause of the issue is playing hopscotch at ever corner of the car and I can't figure out how this many things went wrong all at once one fateful Sunday morning, but now it does turn over.

I'm gonna speculate bad starter and/or battery and/or connection from batter to starter + bad sensor + bad SKIM = my problems but I can't verify the sensors until tomorrow when that little USB port with alligator clips comes in. Fingers crossed for then.
 
The light weirdness is probably the multifunction switch on the column going out.

The fact that it was just clicking and then cranked is a battery, cables, or ground issue. Once you get that squared away, if you still have a crank, no start, time to start looking at the sensors, PCM. Sometimes, they will not run with a weak battery, bad cables even though they will crank. If you have another battery that you can jumper to it, I would try that as well.

No tach during cranking could be the crank sensor,

You can run the gauge cluster test by holding down the odo reset button and then turning the key to ON. Release the odo reset and all the gauges and lights will run through self test.

You can see if the PCM has stored any codes by turning the key ON OFF ON OFF ON very quickly and they PCM will display the codes in the odometer.
 
The light weirdness is probably the multifunction switch on the column going out.

The fact that it was just clicking and then cranked is a battery, cables, or ground issue. Once you get that squared away, if you still have a crank, no start, time to start looking at the sensors, PCM. Sometimes, they will not run with a weak battery, bad cables even though they will crank. If you have another battery that you can jumper to it, I would try that as well.

No tach during cranking could be the crank sensor,

You can run the gauge cluster test by holding down the odo reset button and then turning the key to ON. Release the odo reset and all the gauges and lights will run through self test.

You can see if the PCM has stored any codes by turning the key ON OFF ON OFF ON very quickly and they PCM will display the codes in the odometer.

The PCM has been giving me a P0445 EVAP code for a while now, but ever since this started happening it won't give me anything when I go on, off, etc. It won't even give me the text it gives when there's no codes to read. (It will usually say something about no codes)

I'm hoping crank or cam sensor as that would be significantly cheaper.
Will check grounds and cables etc. as well as gauge cluster test.

Thanks, man.

EDIT: Also it's worth mentioning that the multifunction switch has worked flawlessly in the years I've owned this Jeep, so I'm suspicious of the sudden timing of this failure.
 
The PCM not responding points to the PCM, assuming it's getting power. You should get "done" when it's finished.

If you know anyone with a code reader you can try connecting to the OBDII port directly. You may be able to borrow one from a parts store as well.
 
So your starter is not cranking when you're turning the key to start?

The starter circuit and headlight controls are simple electric circuits that do not interact with the PCM or SKIM. Sounds like you might have a bad ground or damaged harness. I would follow the wiring diagrams in the factory service manual and start tracing out these circuits.
 
So your starter is not cranking when you're turning the key to start?

The starter circuit and headlight controls are simple electric circuits that do not interact with the PCM or SKIM. Sounds like you might have a bad ground or damaged harness. I would follow the wiring diagrams in the factory service manual and start tracing out these circuits.

This has been quite a rollercoaster, and the symptoms have been erratic, so to be clear: It has now turned into a crank, no start, no gauges condition. And the headlight switch also apparently happens to be broken which is some nice organic pink himalayan salt in the wound. So the starter is now working sometimes.
 
Battery tested bad, so new one in and it now cranks without a 200 amp gun to its head. Still no start. Cam sensor checks out, and starter's all good. Still no idea what's wrong with the lights, but I was able to check the crank sensor by hooking up the 5V cord up to it, hook up the multimeter to both the sensor and the 5V cord, and have someone spin the motor (now that it cranks) and can confirm that the CPS is giving no voltage drop at all when the motor spins. Thus finally explaining it (hopefully)

At the very least, I do know that it's bad. It doesn't explain why the car wouldn't let me even crank it, or why it was throwing a no key light at me, but who knows? Maybe the SKIM and CPS failed at EXACTLY the same time. I'm sure weirding things have happened. Or maybe it was just the battery doing the key light. I really don't know. Still worried about the lack of gauges. I did do the odo reset on them and that didn't seem to change anything.

Thanks for your help, fellas. Can't believe this whole time it was the default answer that didn't seem to apply to me at all at first.
 
Well I'm not sure if anyone is still watching this thread, but I hooked up the new crank position sensor and no change. No gauges, no start. Relays check out, battery and starter are good, fuses look good. Crank and cam sensors are good. I don't know why it won't start.

I'm gonna get the voltmeter out and check the crank sensor again. If it's still not reading then I'm lost.

Got the neg terminal unhooked and am letting the computer reset just because, but at this point I think something else is the problem. I'm out of ideas y'all. The old sensor tested bad, which is weird to me, but it did need replacing so maybe when I hook the battery back up it'll fire up no problem but I'm totally at a loss. If anyone has any info to provide please let me know.
 
Maybe you are experiencing the same thing I had. The connector in the steering column had melted and caused all sorts of strange electrical gremlins.

The electrical issues were intermittent and frustrating to diagnose. It’s worth checking at the very least. Good luck.
A38CA056-8212-4ED9-B670-1FE81E4FB250.jpeg
 
Awesome, man. Up until now I've only heard different takes on which multimeter lead goes to which cavity, but haven't actually been told which cavity serves which purpose. I've got a 4.0 standard so that's no biggie.

And just to make sure, I should use a 5V power supply to test the sensor itself, and use the battery with the key on to test continuity between the harness-side and the PCM connection? In the video he uses a screwdriver to interrupt the magnet in the cam sensor to see if it reads. How should I replicate this with the crank sensor?

With any luck, I'll find that one or both of my sensors is trashed and I don't have to drop 1,200 Hopes and Dreams on a new PCM.

Sorry I missed this earlier, sounds like you got past these questions but I'll answer for posterity. I used an external 5V supply because I wanted to be able to bench test away from a vehicle. And also because I thought it was cool to use a phone charger for this purpose....and helped me realize that in a pinch I could use a phone charger to fix a 5V supply problem on the trail or something. But you could absolutely use the 5V supply from the PCM to test the sensor if you wanted to.

And to your comment about nobody telling you what the wires do...yeah, that's part of how the shroud of auto electronics remains in place. It's lots of "just probe the chartreuse wire with the sage trace" or " touch your voltmeter to pin 1" without any indication of why you're doing it or what you should expect. With the variations in wiring across the years, to me it just makes more sense to describe the steps in terms of purpose & goal: "probe the 5V supply from the PCM" which is much more clear on what to do, with the tradeoff of you now have to understand the pinout/cavity map of the connector. But if you start to understand that piece by piece, the mystery slowly evaporates. Also if you were testing the cam sensor on a 97, the 5V & sensor signal are reverse from later years... but if you blindly just stick the probe in cavity 1 you might get a misleading result. I could talk about this long past the point where you'd be bored (like now, for instance).
 
  • Like
Reactions: Bane
Maybe you are experiencing the same thing I had. The connector in the steering column had melted and caused all sorts of strange electrical gremlins.

The electrical issues were intermittent and frustrating to diagnose. It’s worth checking at the very least. Good luck.
View attachment 407992
Well son of a gun.

I've had the multifunction assembly out two or three times now and never noticed the connector going back in, but sure enough it looks just like yours.
What all does that particular connector communicate with and how hard is the replacement? Do all those wires go into a harness somewhere else that I replace as a whole unit, or do I have to splice all new ones in?
 
Well son of a gun.

I've had the multifunction assembly out two or three times now and never noticed the connector going back in, but sure enough it looks just like yours.
What all does that particular connector communicate with and how hard is the replacement? Do all those wires go into a harness somewhere else that I replace as a whole unit, or do I have to splice all new ones in?

The old plug pretty much fell apart in my hand. There is a “kit” I found that supplies a new one. The kit came with a wiring harness that I didn’t use.

Just replace one wire at a time and it’s super easy. See the attached photo for the wiring diagram to see what wire powers what.

48FBE94F-E631-444D-899C-13E882371FC9.jpeg
 
  • Like
Reactions: Bane
The old plug pretty much fell apart in my hand. There is a “kit” I found that supplies a new one. The kit came with a wiring harness that I didn’t use.

Just replace one wire at a time and it’s super easy. See the attached photo for the wiring diagram to see what wire powers what.

View attachment 408099

You have a hard copy of the FSM?!