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Jeep died while driving

C

ChuckstrPT

NAXJA Member #791
Location
Birmingham, Alabama
So, '01 Sport 4.0 AW4 231, driving it down my street and it dies. It had just run 20 min on the highway. Just died. It'll turn over, but no starting. I think I saw "no bus" on the odometer in the middle of all the excitement. I've checked all the major fuses under the hood and they all tested good, looked for loose connectors and found none, unplugged the computer and that all looked good. It turns over fine, but won't fire. Any help is much appreciated! I'm off to the FSM :)
 
Fuel Pump? Any CEL? Crank/Cam Sensor?

I would start with the major "3"........Is it getting AIR, SPARK, FUEL....then work your way into more detail from there. I usually can narrow any non-start issue using that simple method.
 
How do you remove the CPS?? It's an '01. I can barely reach it with on hand, and the pigtail goes down and back alongside the tranny?? Can't really reach it from below.
 
You'll need 2-3 long extensions with a wobbly and a 11mm socket and go from behind the front d/s tire and b/t the tranny and front driveshaft to get to it. There are two bolts holding it in. There's a plastic surround that is loosely snapped into place that the CKP drops into. Don't let it move and don't drop the bolts in the bellhousing if it moves.
 
Last edited:
gradon said:
You'll need 2-3 long extensions with a wobbly and a 11mm socket and go from behind the front d/s tire and b/t the tranny and front driveshaft to get to it. There are two bolts holding it in. There's a plastic surround that is loosely snapped into place that the CKP drops into. Don't let it move and don't drop the bolts in the bellhousing if it moves.
Click to expand...

This. I used a magnet to catch these bolts.
 
I have looked at my 01 CPS and I would probably try to attack the mounting bolt/nut from above thru the engine bay.
As for the connectors, they are attached to a bracket which is attached to the left front side of the transmission , which I would attack from underneath the Jeep... either way it don't look easy.
 
gradon said:
You'll need 2-3 long extensions with a wobbly and a 11mm socket and go from behind the front d/s tire and b/t the tranny and front driveshaft to get to it. There are two bolts holding it in. There's a plastic surround that is loosely snapped into place that the CKP drops into. Don't let it move and don't drop the bolts in the bellhousing if it moves.
Click to expand...

So, if I'm underneath, and 2-3 extensions away from the bolts, how do you not let them move, or avoid dropping the bolts?
 
Here's a good start for removing the CPS: http://www.cherokeeforum.com/f51/jeep-cherokee-2000-4-0l-replace-crankshaft-position-sensor-17310/

Did you test the CPS before deciding to replace it? There's a few things that could cause the problems you described, the CPS is the most common but not the only culprit and most people can't afford to throw $70 parts at their Jeeps until the problem is solved. Here's one CPS test method:

  1. Backprobe with a high impedance ohmmeter between the CKP sensor connector middle terminal and battery ground.
  2. Verify that the resistance is less than 5 ohms. If the resistance is not as specified, repair or replace the wiring as necessary and continue the test.
  3. With the ignition ON and the engine OFF, backprobe with a high impedance voltmeter between the sensor connector middle terminal and either of the end terminals.
  4. Verify that a 5 volt or greater signal is present at one of the two terminals. If not as specified, repair or replace the wiring as necessary and continue the test.
  5. With the ignition ON and the engine OFF, backprobe with a high impedance voltmeter between the sensor connector middle terminal and the end terminal that did not have the 5 volt or greater signal.
  6. Crank the engine and verify that the voltage reading alternates between 0.0 and 5.0 volts or verify that the voltage reading is 2.5 volts (averaging voltmeters only).
  7. If the voltage readings are not as specified, the sensor may be faulty


    Hope this helps.
 
Sounds like a classic CPS failure. Check the SEC thread as I outlined how I removed the CPS.
 
morelia1976 said:
Here's a good start for removing the CPS: http://www.cherokeeforum.com/f51/jeep-cherokee-2000-4-0l-replace-crankshaft-position-sensor-17310/

Did you test the CPS before deciding to replace it? There's a few things that could cause the problems you described, the CPS is the most common but not the only culprit and most people can't afford to throw $70 parts at their Jeeps until the problem is solved. Here's one CPS test method:

  1. Backprobe with a high impedance ohmmeter between the CKP sensor connector middle terminal and battery ground.
  2. Verify that the resistance is less than 5 ohms. If the resistance is not as specified, repair or replace the wiring as necessary and continue the test.
  3. With the ignition ON and the engine OFF, backprobe with a high impedance voltmeter between the sensor connector middle terminal and either of the end terminals.
  4. Verify that a 5 volt or greater signal is present at one of the two terminals. If not as specified, repair or replace the wiring as necessary and continue the test.
  5. With the ignition ON and the engine OFF, backprobe with a high impedance voltmeter between the sensor connector middle terminal and the end terminal that did not have the 5 volt or greater signal.
  6. Crank the engine and verify that the voltage reading alternates between 0.0 and 5.0 volts or verify that the voltage reading is 2.5 volts (averaging voltmeters only).
  7. If the voltage readings are not as specified, the sensor may be faulty


    Hope this helps.
Click to expand...

Unfortunately, it doesn't look like I can test it without taking it out. The wire is too far up. I can only reach it with one hand. So, I'm thinking, if I've got to take it out, might as well have a new part on hand, and replace it. Although, if I can't get it moving early tomorrow, there won't be any urgency, as my DD will be back from the mechanic... blowing cold air in my face again! The jeep died doing Back Up duties!
Thanks for the input!
 
So, just replaced CPS. Thank you for the suggestions to drop the tranny crossmember. That made all the difference in working room in there! But, still no go. It cranks fine, but won't start. The odometer is telling me "no bus"? Any idea where that points me?
Thank you!
 
From some online searching, here is a long, long discussion:

http://www.justanswer.com/jeep/5sxub-jeep-cherokee-2001-jeep-cherokee-sport-no-bus-no-start-4.html

It does suggest disconnecting all the varioius modules one at a time with the key on. If you disconnect a module and the BUS error goes away...that points toward the area at fault (maybe the module).

Also suggested is to look at the inhibitor switch (neutral safety/back up lamp switch). I know mine will fault and throw a code every now and then. There is a cleaning how-to on this site somewhere....
 
Check Fuse #11 in the passenger side kick panel.
Junctionblock.png
Junctionblock.png

JtecPinout.png

Also Check Pins A2 (switched from fuse #11 in the kick panel) and A22 (constant from engine bay fuse block #21) for power to the ECU.
97xjwiring.png
 
Thanks for the input! It's still dead. I hadn't thought about the NSS. I thought that you could still start in Neutral (not in Park) with that switch being bad? I have not checked the fuses in the passenger footwell, but did check all the fuses under the hood.
Thanks again, but I won't be able to get to it until some time next week. We just started the "7 on" part of the 7on/7off routine. :viking:
 
Wow this is old. I can't believe how long it's been. BUT, it's alive again! Found a bad ground at the ECU... after a year, and much wiring harness checking (not by me, that is beyond my skill set.). Don't have it back. They said the dash isn't working, "but you knew that." No, it was working when the truck died.... so they still have it, but it runs! Woo Hoo! Getting closer.........
 
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