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Jeep shuts off, I searched

AaronJXJ

NAXJA Forum User
Location
windsor ct
I have a 2001 xj 4.0 auto, and for the past 4-5 mornings it shuts down on me on my way to work, same street, about a mile and a half from my house. No check engine light. I let it sit for 15 mins and it starts right up, if I try and start it before 15 mins it will crank and crank but not turn over. After it starts I can drive the rest of the 2 miles to work no problems, and I can drive home after work no problems.... I'm stumped, no one seems to have the same symptoms as me
 
Cranking and not starting is typically the CPS failing. Perform some diagnostic tests.


The most likely cause of it cranks and cranks but won't start up is the Crankshaft Position Sensor (CPS) located on the transmission bell housing. Often this part is also referred to as the CranKshaft Position Sensor (CKP) CPS/CKP failure is very common. The CPS/CKP can stop working with no warning or symptoms and the engine will not run or the engine may randomly stall for no apparent reason.

Typical Symptoms –
- Starter cranks and cranks but engine won't start up and run.
- Fuel gauge and voltage gauge may not work or display properly.
- You sometimes will have No Bus on the odometer after 30-60 seconds.
- A failed CPS/CKP may or may not throw a CEL trouble code.
- No spark at the spark plugs.
- Fuel pump should run and prime for 3-5 seconds.

Begin with basic trouble shooting of the start and charge systems. Remove, clean, and firmly reconnect all the wires and cables to the battery, starter, and alternator. Look for corroded or damaged cables or connectors and replace as needed. Do the same for the grounding wires from the starter to engine block, and from the battery and engine to the Jeep's frame/body. You must remove, scrape, and clean until shiny, the cable/wire ends, and whatever they bolt to. Jeeps do not tolerate low voltage, bad connections, or poor grounds and the ECM/ECU may behave oddly until you remedy this.

Exchange the fuel pump relay and the ASD relay with one of the other similar ones in the PDC to eliminate the relays as the cause of the no-start. Check the ASD relay fuse.

Confirm that the fuel pump to runs for 3-5 seconds when you turn the ignition key to ON.

Eliminate the NSS as a cause of no start. Wiggle the shift lever at the same time you try to start. Put the transmission in Neutral and do the same. Do the reverse lights come on when the shifter is in Reverse?

Inspect the wires and wire connectors at the O2 sensors on the exhausts pipe. A short circuit from melted insulation or from broken O2 sensor wires can blow a fuse and the ECU/ECM will loose communication. Don’t get tunnel vision and assume the sensor is bad (unless it tests bad with a meter). Damaged wiring or a dirty connector can inhibit the signal from making it to the computer. Inspect/test/clean/repair wiring or connectors as necessary.



If the CPS/CKP is failed sometimes the OBD-II trouble code reader cannot make a connection to the ECU/computer or cannot read Check Engine Light/MIL codes because the CPS/CKP has failed. Disconnect the code reader, disconnect the CPS/CKP wire connector, and reconnect the code reader. If the code reader establishes contact with the ECU and scans, your CPS/CKP is failed and needs to be replaced.

Crank Position Sensors can have intermittent “thermal failure”. This means that the CPS/CKP fails when the engine gets hot, but works again (and will test as “good”) when it cools back down.

Diagnostic steps to confirm the CPS is the cause of your no-start


1) You should be able to verify a bad cps, by unplugging it, and turning the ignition key to on. If the voltage gauge and/or the fuel gauge now display correctly and/or the No-Bus is gone, replace the CPS.

2) If the CEL does not come on when the key is turned to the RUN position... then the CPS/CKP is bad.


3) Unplugging and reconnecting the CPS sensor where it connect to the main harness near the back of the intake manifold usually resets the ECU and if the jeep fires right up after doing this you can bet that the CPS is faulty and needs to be replaced.

The 2000 and 2001 will have the CPS in the same location on the bell housing, but the wire connector is near the Transfer Case, not as shown in the diagram below. Simply follow the wire from the sensor to the connector.



CPS Testing


Crankshaft Position Sensor Connector (CPS/CKP)


standard.jpg

.
standard.jpg



TESTING PROCEDURE 1991 – 2001 4.0L H.O. engines

1. Near the rear of intake manifold, disconnect sensor pigtail harness connector from main wiring harness.
2. Place an ohmmeter across terminals B and C (See Image). Ohmmeter should be set to 1K-to-1OK scale for this test.
3. The meter reading should be open (infinite resistance). Replace sensor if a low resistance is indicated.

TESTING PROCECURE for 1987 – 1990 4.0 L engines

Test # 1 - Get a volt/ohm meter and set it to read 0 - 500 ohms. Unplug the CPS and measure across the CPS connector's A & B leads. Your meter should show a CPS resistance of between 125 – 275 Ohms. . If the CPS is out of that range by much, replace it.

Test # 2 - You'll need a helper for this one. Set the volt/ohm meter to read 0 - 5 AC volts or the closest AC Volts scale your meter has to this range. Measure across the CPS leads for voltage generated as your helper cranks the engine. (The engine can't fire up without the CPS connected but watch for moving parts just the same!) The meter should show .5 - .8 VAC when cranking. (That's between 1/2 and 1 volt AC.) If it's below .5vac, replace it.

.
standard.jpg

.
 
Tim I actually came across all that in my searching, didn't think it applied to me due to the consistency of my issue and I didn't think it was heat related because it happens so close to my house, but non the less I'll look into it now, I appreciate you taking the time to repost that information
 
I've had identical failures to yours and one time it was the CPS and the other time it was a clogged fuel filter.
 
Crank sensor is absolutely a primary suspect. It is not uncommon for them to suffer from "thermal failure" (heat related) and they won't work until they cool down again.

You could try to replicate it by using a hair dryer on that sensor while you are in the driveway and see if the engine dies.
 
A hair dyer? :roflmao:

It's tough enough to get a wobble socket on a 12" extension near that sensor, let alone a 2" diameter hair dryer.... ;)
 
i also had this issue just more randomly. and same as the_weirdo once it was the CPS and the other time my fuel pump was in and out.
 
The CPS diagnostic above is fairly specific and has several checks and tests, some slightly technical, and some dead simple, that will either include or exclude the CPS as the root cause of the no-start. If the no-start isn't a CPS fault, you should know right away.

Testing the fuel pump can be as simple as listening for it to run when the key is turned to ON. Testing the fuel pressure is also simple.
 
Last edited:
I was having the same problems replaced the CPS and all was good for a while now it still does it everyonce and a while. i will have to check my fuel pump and filter.
 
Cranking and not starting is typically the CPS failing. Perform some diagnostic tests.


The most likely cause of it cranks and cranks but won't start up is the Crankshaft Position Sensor (CPS) located on the transmission bell housing. Often this part is also referred to as the CranKshaft Position Sensor (CKP) CPS/CKP failure is very common. The CPS/CKP can stop working with no warning or symptoms and the engine will not run or the engine may randomly stall for no apparent reason.

Typical Symptoms –
- Starter cranks and cranks but engine won't start up and run.
- Fuel gauge and voltage gauge may not work or display properly.
- You sometimes will have No Bus on the odometer after 30-60 seconds.
- A failed CPS/CKP may or may not throw a CEL trouble code.
- No spark at the spark plugs.
- Fuel pump should run and prime for 3-5 seconds.

Begin with basic trouble shooting of the start and charge systems. Remove, clean, and firmly reconnect all the wires and cables to the battery, starter, and alternator. Look for corroded or damaged cables or connectors and replace as needed. Do the same for the grounding wires from the starter to engine block, and from the battery and engine to the Jeep's frame/body. You must remove, scrape, and clean until shiny, the cable/wire ends, and whatever they bolt to. Jeeps do not tolerate low voltage, bad connections, or poor grounds and the ECM/ECU may behave oddly until you remedy this.

Exchange the fuel pump relay and the ASD relay with one of the other similar ones in the PDC to eliminate the relays as the cause of the no-start. Check the ASD relay fuse.

Confirm that the fuel pump to runs for 3-5 seconds when you turn the ignition key to ON.

Eliminate the NSS as a cause of no start. Wiggle the shift lever at the same time you try to start. Put the transmission in Neutral and do the same. Do the reverse lights come on when the shifter is in Reverse?

Inspect the wires and wire connectors at the O2 sensors on the exhausts pipe. A short circuit from melted insulation or from broken O2 sensor wires can blow a fuse and the ECU/ECM will loose communication. Don’t get tunnel vision and assume the sensor is bad (unless it tests bad with a meter). Damaged wiring or a dirty connector can inhibit the signal from making it to the computer. Inspect/test/clean/repair wiring or connectors as necessary.



If the CPS/CKP is failed sometimes the OBD-II trouble code reader cannot make a connection to the ECU/computer or cannot read Check Engine Light/MIL codes because the CPS/CKP has failed. Disconnect the code reader, disconnect the CPS/CKP wire connector, and reconnect the code reader. If the code reader establishes contact with the ECU and scans, your CPS/CKP is failed and needs to be replaced.

Crank Position Sensors can have intermittent “thermal failure”. This means that the CPS/CKP fails when the engine gets hot, but works again (and will test as “good”) when it cools back down.

Diagnostic steps to confirm the CPS is the cause of your no-start


1) You should be able to verify a bad cps, by unplugging it, and turning the ignition key to on. If the voltage gauge and/or the fuel gauge now display correctly and/or the No-Bus is gone, replace the CPS.

2) If the CEL does not come on when the key is turned to the RUN position... then the CPS/CKP is bad.


3) Unplugging and reconnecting the CPS sensor where it connect to the main harness near the back of the intake manifold usually resets the ECU and if the jeep fires right up after doing this you can bet that the CPS is faulty and needs to be replaced.

The 2000 and 2001 will have the CPS in the same location on the bell housing, but the wire connector is near the Transfer Case, not as shown in the diagram below. Simply follow the wire from the sensor to the connector.



CPS Testing


Crankshaft Position Sensor Connector (CPS/CKP)


standard.jpg

.
standard.jpg



TESTING PROCEDURE 1991 – 2001 4.0L H.O. engines

1. Near the rear of intake manifold, disconnect sensor pigtail harness connector from main wiring harness.
2. Place an ohmmeter across terminals B and C (See Image). Ohmmeter should be set to 1K-to-1OK scale for this test.
3. The meter reading should be open (infinite resistance). Replace sensor if a low resistance is indicated.

TESTING PROCECURE for 1987 – 1990 4.0 L engines

Test # 1 - Get a volt/ohm meter and set it to read 0 - 500 ohms. Unplug the CPS and measure across the CPS connector's A & B leads. Your meter should show a CPS resistance of between 125 – 275 Ohms. . If the CPS is out of that range by much, replace it.

Test # 2 - You'll need a helper for this one. Set the volt/ohm meter to read 0 - 5 AC volts or the closest AC Volts scale your meter has to this range. Measure across the CPS leads for voltage generated as your helper cranks the engine. (The engine can't fire up without the CPS connected but watch for moving parts just the same!) The meter should show .5 - .8 VAC when cranking. (That's between 1/2 and 1 volt AC.) If it's below .5vac, replace it.

.
standard.jpg

.


Thank you for this. I tried this first and it fixed the problems I've been having. CPS replaced and Jeep runs like a dream.
 
Hey,
I have been having issues recently with my 2000 xj shutting off while driving. Usually I can put it in park and crank it and it will turn back on. When it dies the tach simply drops, no sputtering or anything it just turns off. I am speculating that it is the CPS but am not sure because it works some of the time. My Jeep did not throw a code except a couple EVAP fuel system leaks and a cylinder 3 misfire. Sorry for repeating any previously asked questions I just want a solid answer.

Thanks in advance
 
That's what happened recently with my 2k, it turned out to be the camshaft sensor.
 
Hey,
I have been having issues recently with my 2000 xj shutting off while driving. Usually I can put it in park and crank it and it will turn back on. When it dies the tach simply drops, no sputtering or anything it just turns off.

The CPS diagnostic above is fairly specific and has several checks and tests, some slightly technical, and some dead simple, that will either include or exclude the CPS as the root cause of the shutting off. If the problem isn't a CPS fault, you will likely know right away.
 
Last edited:
Hey,
I have been having issues recently with my 2000 xj shutting off while driving. Usually I can put it in park and crank it and it will turn back on. When it dies the tach simply drops, no sputtering or anything it just turns off. I am speculating that it is the CPS but am not sure because it works some of the time. My Jeep did not throw a code except a couple EVAP fuel system leaks and a cylinder 3 misfire. Sorry for repeating any previously asked questions I just want a solid answer.

Thanks in advance

'00 was kind of doing the same thing. When she would reach operating temperature. Pretty sure my CPS was experiencing thermal failure.
Doing the resistance test it came up good, assuming I did it right, but that kind of makes sense cause it was done when cold.
Can read a little more about my experience with it here.

https://www.cherokeeforum.com/f2/cuts-out-while-driving-241745/
 
Good evening, I hope maybe one of you guys can point me in the right direction. My 98 had a dead battery, I jump started it the other day to move it up into the garage to replace the badly cracked APN header. Today I stuck the charger on it, turned the charger to high amp for engine start, it did not start. It cranks, but will not fire. The fuel gauge doesn’t register, the volt gauge reads nothing, the ASD relay and the fuel pump relay do not pull in. All fuses check good. I pulled a cover off a relay, stuck it in fuel pump slot, tripped it, fuel pump does run. I unplugged the CPS, the one on the fly wheel, it did not change anything. The CPS ohm’s open. Where should I look next? Could I have fried the ECM, when I turned the charger to boost or when I ran it on a dead battery after I jump started it?
Thanks in advance for your help!
 
The symptoms suggest a faulty CPS, or another OBD-II sensor that is short circuited, but you should always suspect the most recent repairs or modifications as a primary suspect. Did you forget to reconnect any OBD engine sensors or wire harness connectors your removed for the repairs ? Have you inspected all the wire plugs for pushed back wire pins or corrosion, inspected all the wire harnesses for chafed/melted wire insulation or any other damages that may have been present, or may have occurred during the repairs ?

I would specifically look at and continuity test: 1) the wire harnesses at the rear of the valve cover, 2) the O2 sensor wire harness, 3) the wire harness for the throttle body and sensors on top of the engine.
 
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