CPS testing procedure 97 XJ sport 4.0

I see many posts on here regarding CPS testing, whether it be excessive cranking no start, unstable idle or poorly running jeep. The testing procedure has been posted several times and from what I have found there seems to be confusion on whether this is the actual problem, therefore people throw money at a new sensor and 50% of the time it simply does not solve the problem. In my case I am having a few issues going on, intermittent starting, delayed shifting (which could be a bad TPS).

The testing procedure for the Crankshaft PS seems to be very straight forward, however, when I attempt to do it I am getting mixed results. One test in particular is the verification of infinite resistance between terminals B and C on the connector leading to the sensor. The test states, with meter set to 1k-10k, to probe the harness at terminals B and C and check for infinite resistance. I am getting varying resistance readings, sometimes 3.5k or 7.5k... this is with meter set to 10k. Now, if I set it to 2k on the meter I am getting infinite resistance. My question is, does it matter if my meter is set to 2k, 10k even 20k?! Should I ever see resistance on any setting? Should it always read infinite no matter what? There doesnt seem to be a clear explanation for this question from what I can find. Thanks for the help.

There is no valid test for the cps from 91 up. It's a hall effect sensor and testing with an ohm meter will not give accurate or valid results.
The Renix years (87-90) cps were simply a induction coil pickup and an ohm test was an approved method.

then this testing procedure has no merit? If not then why do I continually see this everytime sometime inquires about testing the sensor?

CRANKSHAFT SENSOR 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. The terminals are identified as A-B-C looking into connector from left to right with the “notch” in the middle of the connector on your right. Ohmmeter should be set to 1K-to-10K scale for this test.

3. The meter reading should be open (infinite resistance). Replace sensor if LOW RESISTANCE

Ohmmeter should be set to the 10 K or 2O K (10,000 or 20,000) scale for this Crankshaft Position Sensor test.


It cannot be said enough times, if you are dealing with Crankshaft Position Sensor (CPS) symptoms, and the CPS is not a genuine Jeep part, it is VERY HIGHLY LIKELY FAULTY.

Ok, I have replaced the CPS with a genuine part, I was able to find one locally. It seems to have helped with the cranking situation, no more long crank/no start issues. I have also replaced the TPS with a genuine part. My issue of accelerating is still somewhat there. When the trans auto shifts through gears while slowing down or speeding up there is a delay in acceleration for example but the RPMs will rise, trans will kick in, the I can feel it accelerate. Its almost like there is something holding the jeep back until it finally gears itself properly then the RPMs drop back down to normal.

The infinite resistance used in the test procedure is not a true infinite, it is an over range reading based on setting the meter to an upper limit of 10K. At that setting a 10.1 K resister will by design read infinite on the meter scale. In that case all infinite means is greater than 10.0 K
Does that help??

So if the CPS read a number under 10K, it was bad per that test. I have read that the test does not confirm a good CPS, but I suspect one testing under 10K is in fact a bad CPS. On both the Renix and HO XJs a bad CPS can still work sometimes, and be not totally dead.

Sounds like you have a real transmission or TCU or wiring problem on the transmission, although the PCM does give the TCU computer some data. Be sure to consider the VSSs (Vehicle speed sensors) input as well. Is this problem in 2WD mode? You might want to read the thread here called something like "Everything you ever wanted to know about the AW4"

Also it may take some driving for the computers to learn the new TPS???

Well, for starts, its a 2wd rig, no 4wd as of yet, I am considering converting, but not anytime soon. I am not entirely certain what to look for in the speed sensors. There is one in the back of the trans and on the side correct?

I've had a couple with thermal failure. Quick and dirty check ( for me ), while still in place, use a funnel pour water on it to cool it down. If the engine starts, that might be it. When it warms back up and engine doesn't start, that's probably the problem.
Once I bought a new "better quality" one from NAPA. It was DOA and confirmed by heating it in the oven and checking, no resistance. Cooled it in ice water, worked fine.
Hope this helps,
Mike

DTW97XJ said:

Ok, I have replaced the CPS with a genuine part, I was able to find one locally. It seems to have helped with the cranking situation, no more long crank/no start issues. I have also replaced the TPS with a genuine part. My issue of accelerating is still somewhat there. When the trans auto shifts through gears while slowing down or speeding up there is a delay in acceleration for example but the RPMs will rise, trans will kick in, the I can feel it accelerate. Its almost like there is something holding the jeep back until it finally gears itself properly then the RPMs drop back down to normal.

Click to expand...

I read the answer to that a week or two ago here and forgot already. Digger87xj has the answers, I just can't find the post he made last month. Also there are other speed sensor names and locations in the later years, OSS is one I just found, output speed sensor? Also the wiring to it could be damaged, exhaust or drive shaft contact!

DTW97XJ said:

then this testing procedure has no merit? If not then why do I continually see this everytime sometime inquires about testing the sensor?

CRANKSHAFT SENSOR 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. The terminals are identified as A-B-C looking into connector from left to right with the “notch” in the middle of the connector on your right. Ohmmeter should be set to 1K-to-10K scale for this test.

3. The meter reading should be open (infinite resistance). Replace sensor if LOW RESISTANCE

Click to expand...

That test is looking for a completely failed CPS. One that is causing a crank, no start condition.

Yours had not completely failed, so the symptoms are different, and that makes the test invalid.

well, it is replaced nonetheless. thanks for all the tips. my next venture is to really figure out this floating RPM situation. It most likely
right under my nose and I cant see it. I spoke with a neighbor and he suggested just a fluid and filter/screen change which I have not done. I was also able to get an extra TCU today and tried a swap, it didnt change a whole lot. Not certain as to which road to take next?

DTW97XJ said:

well, it is replaced nonetheless. thanks for all the tips. my next venture is to really figure out this floating RPM situation. It most likely
right under my nose and I cant see it. I spoke with a neighbor and he suggested just a fluid and filter/screen change which I have not done. I was also able to get an extra TCU today and tried a swap, it didnt change a whole lot. Not certain as to which road to take next?

Click to expand...

AX15 with TC..........and be done with it.



Then you'll be ready for a full swap.

bout too at this point...this is keepin me up at night

DTW97XJ said:

well, it is replaced nonetheless. thanks for all the tips. my next venture is to really figure out this floating RPM situation. It most likely
right under my nose and I cant see it. I spoke with a neighbor and he suggested just a fluid and filter/screen change which I have not done. I was also able to get an extra TCU today and tried a swap, it didnt change a whole lot. Not certain as to which road to take next?

Click to expand...

Loose dirty sensor wire grounds at the oil dipstick?

TPS or TPS wiring, connector, or the AW4 connector to the transmission near the dip stick?

Change the filter and fluid (several times) with a 1/2 pint of Trans-X each time.

There is no ground point at dipstick on this 97, just a ground point at coil. I will keep chasing wires and checking harnesses. It is has to be something quite obvious I just dont see it yet. fluid and filter/screen change is next for sure, thinking about doing solenoids while i am in there

DTW97XJ said:

There is no ground point at dipstick on this 97, just a ground point at coil.

Click to expand...

1997 XJs have three different grounds on the passenger side of the engine. The fuel injection, coil and sensors all ground at one of them.

DTW97XJ said:

There is no ground point at dipstick on this 97, just a ground point at coil. I will keep chasing wires and checking harnesses. It is has to be something quite obvious I just dont see it yet. fluid and filter/screen change is next for sure, thinking about doing solenoids while i am in there

Click to expand...

That may be the problem?

Say again?!

This is my setup, I do see a wire attached to block about 5 inches up from there but there are only two wires. Not sure how to post a pic on here otherwiseI would.

DTW97XJ said:

This is my setup, I do see a wire attached to block about 5 inches up from there but there are only two wires. Not sure how to post a pic on here otherwiseI would.

Click to expand...

Should be three rings with 3-4 small wires total and a huge starter ground wire all on one engine block post near the oil dip stick (holder) on the passenger side.