T.j. Leath

So I have a 96 Grand Cherokee Limited runs perfectly fine for a few days and then every once in awhile when I stop at a light it just completely dies pretty much like I just turn the key off any suggestions don't feel like just throwing Parts at it

gat

When I had that symptom it was the crankshaft position sensor.

lawsoncl

I vote Crank Position Sensor as well. Fairly common problem.

Side note - there is a Grand Cherokee specific forum https://www.cherokeeforum.com/f5

Ralph77

I would guess the Crank Positioning Sensor also.
This is for a '00 XJ but my experience with it.

https://www.cherokeeforum.com/f2/cut...riving-241745/

XJlimitedx99

CPS gave me a similar symptom. Although, it happened while driving for me. Wasn't specific to stopped.

I don't know of a way to diagnose a bad sensor. If you replace it, make sure to use a Mopar sensor, not a generic parts store brand! This is arguably the most important sensor on the vehicle and our Jeeps tend to be very sensitive to the sensors installed on them. I know its more money but it'll be money well spent. I only use authentic Mopar sensors.

Ralph77

As far as an XJ goes there is this video:


Would this be the same for a Grand Cherokee? Not a clue.
The test would not work for me though cause my problem was thermal failure of the CPS.
At least that is what I believe was the problem.
So unless I could check it at the exact moment it screwed up I would get a good reading.

dave1123

The main difference between a Mopar CPS and an aftermarket one is the magnet. Mopar uses a neodymium magnet and aftermarket ones don't. Since this is a magnetic switch, I think the magnet is the most important part, what do you think?

The CPS is a Hall-effect switch that reads changes in it's magnetic field caused by metallic objects passing close by it. There are "windows" in the flexplate positioned so that each pair is at TDC for each cylinder and the computer uses these pulses to set ignition timing. Do you see how important it is?

lawsoncl

The CPS typically has two failure modes. The sensor gets weak and doesn't put a strong signal at idle (the strength of the pulses from the sensor depend on the rpm), so you can get no-start or dying at idle. They can also be heat sensitive and intermittently drop out when they get hot, resulting in stalling while driving and it will typically start again once it cools a bit. Typically, you will not get a check engine code set.

dave1123

Yeah, you'll only get a code when it dies completely, as in no signal at all. (P0336)