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  #1  
Old February 8th, 2012, 05:39
AaronJXJ AaronJXJ is offline
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Jeep shuts off, I searched

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
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  #2  
Old February 8th, 2012, 06:05
CASEY-R CASEY-R is offline
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When my '97 was shutting down it was more random but ended up being the fuel pump.

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  #3  
Old February 8th, 2012, 10:49
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Tim_MN Tim_MN is offline
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Re: Jeep shuts off, I searched

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)



.



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.

.

.
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Quote:
Originally Posted by bimmerjeeper

Go ahead and slam the liftgate down on a blanket, and see how long you are laughing.
Quote:
Originally Posted by soyjer

Tim MAY be 100% correct, but why would a person automatically pick him as the expert .....
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  #4  
Old February 8th, 2012, 12:05
AaronJXJ AaronJXJ is offline
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Re: Jeep shuts off, I searched

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
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  #5  
Old February 8th, 2012, 13:26
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the_weirdo the_weirdo is offline
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Re: Jeep shuts off, I searched

I've had identical failures to yours and one time it was the CPS and the other time it was a clogged fuel filter.
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  #6  
Old February 8th, 2012, 16:48
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birchlakeXJ birchlakeXJ is offline
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Re: Jeep shuts off, I searched

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.
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  #7  
Old February 8th, 2012, 21:46
CJ7Pilot CJ7Pilot is offline
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Re: Jeep shuts off, I searched

A hair dyer?

It's tough enough to get a wobble socket on a 12" extension near that sensor, let alone a 2" diameter hair dryer....
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  #8  
Old February 9th, 2012, 09:16
halvey88 halvey88 is offline
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Re: Jeep shuts off, I searched

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.
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  #9  
Old February 9th, 2012, 10:38
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Tim_MN Tim_MN is offline
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Re: Jeep shuts off, I searched

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.
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.

Quote:
Originally Posted by bimmerjeeper

Go ahead and slam the liftgate down on a blanket, and see how long you are laughing.
Quote:
Originally Posted by soyjer

Tim MAY be 100% correct, but why would a person automatically pick him as the expert .....

Last edited by Tim_MN; November 3rd, 2019 at 07:55.
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  #10  
Old February 10th, 2012, 05:25
AaronJXJ AaronJXJ is offline
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Re: Jeep shuts off, I searched

Hey I just wanna thank everyone for there help, new CPS and it's been running like a champ for 2 days now
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  #11  
Old March 3rd, 2012, 12:47
bobyep bobyep is offline
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Re: Jeep shuts off, I searched

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.
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  #12  
Old September 21st, 2019, 22:50
JeepXJFan JeepXJFan is offline
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Re: Jeep shuts off, I searched

Quote:
Originally Posted by Tim_MN View Post
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)



.



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.

.

.

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.
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  #13  
Old October 30th, 2019, 16:44
blackxjmn blackxjmn is offline
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Re: Jeep shuts off, I searched

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
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  #14  
Old October 30th, 2019, 16:46
RCP Phx RCP Phx is offline
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Re: Jeep shuts off, I searched

That's what happened recently with my 2k, it turned out to be the camshaft sensor.
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  #15  
Old October 30th, 2019, 17:01
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Tim_MN Tim_MN is offline
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Re: Jeep shuts off, I searched

Quote:
Originally Posted by blackxjmn View Post
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.
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.

Quote:
Originally Posted by bimmerjeeper

Go ahead and slam the liftgate down on a blanket, and see how long you are laughing.
Quote:
Originally Posted by soyjer

Tim MAY be 100% correct, but why would a person automatically pick him as the expert .....

Last edited by Tim_MN; October 30th, 2019 at 17:10.
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