myjeepisDEAD

Hey Jeep Friends!

Does anybody know if there is a difference between a CPS for a manual trans and a CPS for an automatic trans? From what I've heard, the exterior between the two may be identical (appearing the be interchangeable) though the inner electronics could be different.

I have been having electrical trouble which was initiated by a faulty CPS. Obviously this is a common problem on Cherokees, so I was able to identify the problem, locate the sensor, and replace it right away. After a month of trying to figure out the no-spark problem and replacing nearly every ignition component we still haven't made much progress, and now we're thinking the new CPS could be the issue.

Thanks!

cherokee country

i had a problem with a 90 4.0 cherokee a few years back. it was a no start issue, an intermittent no start problem. drove it to a shop(yes it actually started that time) and they found the crank position sensor to be at fault. they found the wires leading to the cps had shorted to ground on the tranny bell housing. new cps and some redirected wiring and problem solved....never had another issue with it. just a thought i hope this helps.

myjeepisDEAD

Thanks for the response! I am thinking the issue could definitely be wiring because I replaced the CPS twice with no avail, but I have a whole other thread for that.

I was just wondering if there's a difference between the CPS on auto trans and CPS on manual trans, or if they're identical.

Craig Weldy

The Manual Sensors are physically shorter than the Automatic Sensors. Not by a lot, but enough that the manual sensors won't be in range to detect the Flex Plate in an auto transmission. If you use an Automatic Transmission sensor in a manual transmission you will have to shim it out a little (about the width of a standard washer) otherwise it will hit the flywheel and get destroyed. These sensors are designed to operate at a very fine distance range away from the flywheel/flex plate about the thickness of 2 credit cards. Most online aftermarket sites selling these sensors don't differ far enough and assume everything fits your year vehicle..Don't get stuck with wrong parts! Rockauto.com will hammer down your vehicle version, engine, transmission, VIN#, etc to get you to the right part. PS. If you buy the Economy parts..well you get what you pay for. It may work for a while.. trust me I know...
(P.S. - Always Always look at inside the connector picture to make sure it is also identical in orientation to the one you have.)

BlueRidgeMark

Do not buy any aftermarket CPS. These things are very picky about sensors, especially that sensor. Mopar only. (Also sold under the NGK or NTK label, since NGK makes them for Mopar.)

There are tons of horror stories here about a new aftermarket CPS being bad out of the box, or failing in a few minutes, or hours... or months. We probably see a new one at least once or twice a month on this forum, and sometimes more.

It can make diagnosis pretty frustrating. You were SURE it was the CPS, and you replaced it with a brand new one, and it still won't start! Now what?

Now your new CPS is bad out of the box, but you'll tear your hair out for three weeks trying to find another problem.

Cummins93

Welcome to the forum. Please provide the different part numbers for the auto and manual CPS. This will help future members on this vintage thread.

PatHenry

A manual Jeep is unlikely to ever need a new CPS. I've got somewhere between 725k-750k miles driven across 3 4.0L Jeeps in my family, all 3 were manuals 2 XJ's with AX15's (400k bought new and ~30k) and 1 TJ (302k bought new) with the NV3550 and have never had a single CPS failure. My theory is that the auto transmission generates a heck of a lot more heat and since the CPS failures seem to be consistently thermal in nature, that's the reason the autos have a problem but the manuals never do.

BlueRidgeMark

Hmmm. Interesting, Pat. You could be on to something there.

PatHenry

My dad bought his 94 XJ brand new, I bought my 00 TJ brand new.. both were DD respectively for roughly 15 years each, I know the TJ is still operational today with the original CPS, so it's possibly coincidence, but likely a sound theory. The 700k miles between the two is a lot of miles. The manual tranny's don't require cooling like the auto does, so right there we know that the auto generates a lot more heat during normal operation.... the normal complaint that turns out to be CPS is "runs fine when cold, as soon as it's up to temp, it cuts out"... well, maybe the manual tranny is cool enough that it never gets "up to the same temp" as the auto does.

I'm interested in hearing if someone that has or had a manual has ever had a CPS failure like what is commonly described.

lawsoncl

Depends on the year. Up to 1990, the Renix era has the same part number. Rock auto shows the same part numbers for 1991-1993, but different ones for 94 -- which makes me wonder since the flex plates are the same?