New Crank Position Sensor bad? - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Cherokee & Comanche Forums > XJ Cherokee Technical Forum > New Crank Position Sensor bad?

Introducing MONSTALINER™ UV Permanent DIY Roll On Bed LineRubicon Express Suspensions from CCOR 706-207-4140Smittybilt Hard Tops @ Oconee Off-Road! 706-534-9955

Reply
Unread 05-27-2009, 08:08 PM   #1
Lone Star XJ
Registered User
1997 XJ Cherokee 
 
Join Date: Sep 2007
Location: The Woodlands, TX
Posts: 48
New Crank Position Sensor bad?

I am still chasing a cyl. 1 misfire. I checked the resistance of the crank position sensor and it read 7.25 Mohms. It would just read .0L ohms and the same when set to kohms. I bought a new sensor and checked the resistance of it. It reads 4.96 kohms and also .0L ohms.

Is my meter jacking with me or what? This is on a 1997 XJ, so the resistance should show 0 ohms (ie. open).

Lone Star XJ is offline   Reply With Quote
Unread 05-27-2009, 08:29 PM   #2
PITBULL1967
Registered User
2013 JK Wrangler 
 
Join Date: Dec 2008
Location: UTAH
Posts: 546
Sounds like there's too much resistance. Lo means there's an open in the circuit.
PITBULL1967 is offline   Reply With Quote
Unread 05-27-2009, 09:01 PM   #3
Lone Star XJ
Registered User
1997 XJ Cherokee 
 
Join Date: Sep 2007
Location: The Woodlands, TX
Posts: 48
That is what I thought. However, this new one has me puzzled. I guess I will go back to the parts place and check another one.
Lone Star XJ is offline   Reply With Quote
Unread 05-28-2009, 09:11 AM   #4
Lone Star XJ
Registered User
1997 XJ Cherokee 
 
Join Date: Sep 2007
Location: The Woodlands, TX
Posts: 48
I went out and checked the sensor this morning after the engine had cooled all night. It was giving me an open reading, 0L. I checked the new one again and it still read 4.96 kohms. I drove to work and checked the resistance again and it was back up to 7.6 Mohms. I am convinced that my meter is giving me an 0L reading when set to ohms and kohms because the resistance is out of range. My meter only reads up to 400 when set to ohms and either 4, 40 or 400 when set to kohms. So I took the new sensor back and ordered a new one. I will give an update when I receive it and check the resistance.
Lone Star XJ is offline   Reply With Quote
Unread 05-28-2009, 09:21 AM   #5
CJ7-Tim
Real Jeeps have dents.
 
CJ7-Tim's Avatar
2000 XJ Cherokee 
 
Join Date: Apr 2002
Location: out in the garage - Minneapolis, Minnesota
Posts: 21,643
The CPS would not be responsible for a single cylinder misfire.


CPS 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. 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.

CPS 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.

.
__________________
.

According to the National Shooting Sports Foundation, AR-15 sporting rifles account for nearly 20% of all U.S. firearms sales.

Progressive Liberalism: Bringing you new Healthcare ideas so wonderful, they have to include mandatory participation ......

Originally Posted by Ronald W. Reagan: Government is not the solution to our problems; Government is the problem.
CJ7-Tim is offline   Reply With Quote
Unread 05-28-2009, 10:02 AM   #6
Lone Star XJ
Registered User
1997 XJ Cherokee 
 
Join Date: Sep 2007
Location: The Woodlands, TX
Posts: 48
Quote:
Originally Posted by CJ7-Tim View Post
The CPS would not be responsible for a single cylinder misfire.


CPS 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. 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.

CPS 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.

.
Thanks Tim. I have been following your test instructions from another post. I didn't think the CPS would be responsible for a single cylinder misfire, but I am trying to go through and test/check everything I can before replacing parts or ultimately taking it to a shop. The resistance changing on me between it sitting over night and when it is warm seems odd to me. I am going to get the new sensor at lunch and check it.
Lone Star XJ is offline   Reply With Quote
Unread 05-28-2009, 07:24 PM   #7
Lone Star XJ
Registered User
1997 XJ Cherokee 
 
Join Date: Sep 2007
Location: The Woodlands, TX
Posts: 48
This should be very simple, but it is driving me nuts. I guess there is something to having the meter set in the 1k ~ 10k range. I don't know why it would mater if you are using a multimeter with an auto range function. Both the old and new sensor read about the same resistance when cold. The resisance of the old one does change after running the engine.

I just tried test #2 in Tims post. I set my meter to the 4 AC volts range which reads down to three decimal places. I had my wife crank the engine and I am only reading 0.006 ~ 0.007 AC v. I am going to say the one on the Jeep is bad and needs to be replaced. I hope this does the trick because it is an expensive part to replace for no reason.
Lone Star XJ is offline   Reply With Quote
Unread 05-28-2009, 07:44 PM   #8
CJ7-Tim
Real Jeeps have dents.
 
CJ7-Tim's Avatar
2000 XJ Cherokee 
 
Join Date: Apr 2002
Location: out in the garage - Minneapolis, Minnesota
Posts: 21,643
Quote:
Originally Posted by Lone Star XJ View Post
The resisance of the old one does change after running the engine......
Take careful note of the range of model years for the two different testing procedures. The cut-off is the difference between OBD-I and OBD-II. You can only get useful results from the test that is for your year of Cherokee.

If one of the CPS you have shows resistance when warm, I suspect that one as starting to fail. The CPS can have thermal failure where it is bad when hot, and tests OK when cool.
__________________
.

According to the National Shooting Sports Foundation, AR-15 sporting rifles account for nearly 20% of all U.S. firearms sales.

Progressive Liberalism: Bringing you new Healthcare ideas so wonderful, they have to include mandatory participation ......

Originally Posted by Ronald W. Reagan: Government is not the solution to our problems; Government is the problem.
CJ7-Tim is offline   Reply With Quote
Unread 05-28-2009, 08:02 PM   #9
Lone Star XJ
Registered User
1997 XJ Cherokee 
 
Join Date: Sep 2007
Location: The Woodlands, TX
Posts: 48
Quote:
Originally Posted by CJ7-Tim View Post
Take careful note of the range of model years for the two different testing procedures. The cut-off is the difference between OBD-I and OBD-II. You can only get useful results from the test that is for your year of Cherokee.

If one of the CPS you have shows resistance when warm, I suspect that one as starting to fail. The CPS can have thermal failure where it is bad when hot, and tests OK when cool.

So soing the voltage test on a 1997 is of no use?
Lone Star XJ is offline   Reply With Quote
Unread 05-28-2009, 08:17 PM   #10
CJ7-Tim
Real Jeeps have dents.
 
CJ7-Tim's Avatar
2000 XJ Cherokee 
 
Join Date: Apr 2002
Location: out in the garage - Minneapolis, Minnesota
Posts: 21,643
I have replaced the CPS on 3 out of 5 of my Cherokees when they failed and the engine would not start. Only one gave me warning by behaving erratically, the others just failed. I am not a Electronics Tech, but there are major differences between the OBD-I and OBD-II self diagnostic systems.
__________________
.

According to the National Shooting Sports Foundation, AR-15 sporting rifles account for nearly 20% of all U.S. firearms sales.

Progressive Liberalism: Bringing you new Healthcare ideas so wonderful, they have to include mandatory participation ......

Originally Posted by Ronald W. Reagan: Government is not the solution to our problems; Government is the problem.
CJ7-Tim is offline   Reply With Quote
Unread 05-28-2009, 08:39 PM   #11
Lone Star XJ
Registered User
1997 XJ Cherokee 
 
Join Date: Sep 2007
Location: The Woodlands, TX
Posts: 48
Well, I am going to go ahead and put the new one on and see what happens. I will report the results.
Lone Star XJ is offline   Reply With Quote
Unread 07-13-2012, 08:09 PM   #12
Jeeper_YJ
Registered User
 
Join Date: Apr 2010
Location: Las Vegas
Posts: 559
Quote:
Originally Posted by CJ7-Tim View Post
The CPS would not be responsible for a single cylinder misfire.


CPS 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. 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.

CPS 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.

.
I know this thread is old. But, I did a search before posting. Give me credit! What is low resistance? Mine is 3.69 on a 1997 XJ
__________________
'97 Cherokee, 99+ intake, 62mm TB, 703 injectors (new), k&n intake, Hypertech III, 180* stat (1/8" drilled hole), 2.5" manifold 2 tail pipe (Hooker Maxflow & hi flow cat), Perf header, 4.5" zone lift, 32" GY Dura Trac, Rear head rests. Comp cam "231" & Perf head (LS1 BIG valves 2.02/1.62). 3 row alum radiator.
Jeeper_YJ is offline   Reply With Quote
Unread 07-14-2012, 03:53 PM   #13
CJ7-Tim
Real Jeeps have dents.
 
CJ7-Tim's Avatar
2000 XJ Cherokee 
 
Join Date: Apr 2002
Location: out in the garage - Minneapolis, Minnesota
Posts: 21,643
Place your meter in the correct test mode settings and touch the probes together. Note the display. Now test your CPS. If you get any reading that is different than just touching the probes together, the CPS is probably faulty.
__________________
.

According to the National Shooting Sports Foundation, AR-15 sporting rifles account for nearly 20% of all U.S. firearms sales.

Progressive Liberalism: Bringing you new Healthcare ideas so wonderful, they have to include mandatory participation ......

Originally Posted by Ronald W. Reagan: Government is not the solution to our problems; Government is the problem.
CJ7-Tim is offline   Reply With Quote
Reply
Thread Tools


Suggested Threads





Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.