The GC is 8cyl and I live in Florida so heat index is always up there. While driving down the road at 45 mph the thing stalls for no reason! Just powers off with no warning plus no check engine light or other warnings. Then it will start anywhere from 1-2 minutes later & was 5 or more the other day. Sometimes it stalls at light too but it doesn't discriminate! Fuel pump replaced & injector cleaner is what mechanic suggested since it is at 187K miles but nope still doing it!

So I took it to where they could run diagnostics for codes etc. $100 & nothing! Told my mechanic about Googling cam shaft or crank shaft sensors. He says no the jeep wouldn't crank if those were bad. He thinks it might be PCM but I am gun shy after spending already $500 & the PCM is not cheap. Need help.

 

Welcome to CF! Glad to help.

It's the crankshaft sensor. He's wrong about it not cranking if it's bad. It won't START if it's bad. The CPS or crankshaft position sensor counts the notches in the flywheel and tells the PCM when to fire the spark plugs. Your symptoms are normal for a failing CPS and one that will soon fail completely. This is just my opinion, but I'd change it before anything else. AND use a genuine Mopar part, not some after-market POS. Check the wiring going to it for chaffing or bare wires. It's mounted on the transmission bellhousing and I believe it's on the passenger's side on top. I also believe you can access it thru a plate in the floor under the heater.

You can test the PCM by moving the cable that comes out of it while the engine is running. If it stalls or misfires when you flex the cable, the connections at the cable plugs may be loose or have broken solder connections inside the unit. Solder connections can be fixed without replacing the PCM.

A bad CPS will not set a check engine light. A bad cam sensor usually sets a misfire code.

 

Where's the CPS of the V8? Happy Dave you responded fast for her, kinda knew you would lol.

 

Here's a couple of pictures of the access hole for the CPS. These may be for the 6 cylinder, but the idea is the same.

 

Thank you so much! Well I felt he (mechanic) wasn't familiar with GC issues enough & although the fuel pump was making a noise & it was original- felt it wasn't money wasted. BUT - I stalled on bridge and guy passing told me it was the CPS. That it heats up & stalls my GC. But I forgot to mention - my daughter is having similar issue with her Volvo but doesn't happen if you don't turn on AC. So I tested this and 30 miles later...wet with sweat-me not Jeep LOL- it did not stall once! My boyfriend drove it yesterday to work & always stalls on him about 10 miles into 14 mile drive- calls to say didn't happen with AC off. Is there a correlation to the placement of the CPS?

 

Is this it?

 

Just talked to mechanic and he said he pulled PCM and wiring was good. He also said he that he tapped the PCM & it would start up but he has not seen this before nor dealt with a GC much so maybe just a coincidence that it started when he tapped PCM. To tell you truth that was my thought because it can start within seconds when I try turn key & other times it takes a few.

 

WHENEVER I read about the issues you are having with your Jeep, I immediately assume it's the PCM. Simply because that is what I experienced with mine. Intermittent stalling, instant restart, start when tapping PCM, but not when wiggling wires. I held back from writing this time because I am not always right. If it is the PCM. Be very careful where you purchase your replacement. Buying one from some fly-by-night company on EB or on line for a couple hundred bucks can cause you more headaches. Even the ones from the major chain auto parts stores can be flaky.

I paid through the roof for mine and went to the stealership. But. I came with a 3 year warranty and I know where they are if I have any problems.

 

I get bored sitting around doing nothing (retired) and happened to be on-line when she posted. I only work 3 nights a week so I'm libel to be on at any time.

As I said, I believe it's on the passenger's side on the bellhousing while the 4.0 it's on the driver's side.

 

Please. We all know anytime someone posts GC on this forum, a red light goes off in your house ;P

 

LMAO! I guess you're right. I live on Grand Cherokee Tech. It's what I know most about, except maybe Chevys. My last Chevy was an 89 4x4 truck. Then I had a K-car and 2 Dodge Caravans, thanks to my wife. After she passed, I started with my jeeps. Everything on my 97 ZJ was beat except the 4.0. It's true you have to blow them up to kill them!

My WJ is as perfect as I can make it, without any major changes except for that damned 0331 head! 180K and still perfect.

I really don't have any personal experience with the 4.7, although I've learned enough about them from this website to make educated guesses.

 

Yo Dave. We may something else in common besides Jeeps. My current other vehicle is a 88 k1500. I just love it. I spend almost zero time on the Chevy Forum as I have almost zero issues with it.

 

sensor is above starter right side

 

crank shaft sensor right side above starter , camshaft sensor right side front bottom of head removel of battery makes getting to it easy

 

Hi Dave- after all repairs my SO is concerned and he has been driving it back & forth to work for past 4 days. He had driven it before & usually stalled. He has suffered through the heat here with his dress clothes getting soaked but not one time has it stalked when a/c isn't running. He thinks it's not a coincidence but wondering why & if still the CPS?