Trouble with the CPS, gauges are going wild!

[ubercurtisb]

On Sunday while driving home, my Jeep just stalled on the road, while I was cruising at about 40mph. I coasted to the center lane, put it in Park, pulled the key out, and then put it back in and it started right up again. "Whoa, WTF? That was weird..." And then it happened 5 more times on the way home. The CEL came on after the third or fourth time, so I pulled into O'Reilly's and had the code read. It showed up as P0320 and P1391. So all fingers are pointing toward the Crankshaft Positioning Sensor. I only use OEM Mopar parts for my Jeep, so this morning I took it in to Tempe Autoplex's Jeep dealership (Stalled about 20 times getting there, but never had trouble starting it right back up) where they pulled the same codes and told me it was the CPS and the Camshaft Positioning Sensor. I don't like to screw around, and I want it done right, so I said "Alright, do it to it."

After waiting 3 hours and paying $360, I got my Jeep back. Drove home with little to no issue, except maybe a minor hiccup, which I assumed was all in my paranoid head. After a few hours of studying for a test, I get back in the Jeep and go to school, and it just didn't feel right. s I got off the freeway, my speedometer went loopy, and went far past the 100mph and then back again, and the oil pressure gauge dropped for a split second, and my "Check Gauges" light came on, and then everything went back to normal. On my way home from school, this happened about 5 more times. All of this was happening as the engine seemed to want to stall, but it didn't. The RPMs, Speedo, and Oil Pressure gauges all went loopy several times. Maybe a misfire or something, I don't know.

I"m worried because all of these symptoms are showing up after replacing these parts that I had the dealer put in. What else could be going on? Could the dealership have missed a step or two? It wasn't doing any of this on Saturday.

Specs: 2001 XJ, 4.0, auto, NP242, 143,xxx miles.

 

[20jeep00]

My crank sensor just took a dump. None of my gauges worked but the mileage showed. Replaced and all is well. As far as your problem I would go back to said dealer and tell them what happened after they worked on it and they "should" check it out at no cost

 

[birchlakeXJ]

Even genuine Mopar parts can fail out of the box. My gut feel is that it's the crankshaft position sensor giving you fits.

Gotta take it back to the dealership and hopefully they will replace the crankshaft position sensor again. This time make sure they perform a thorough inspection of the wiring/connector to make sure you're not missing something.

 

[kastein]

Check your wiring harness where it goes over the transfer case and rear driveshaft to the rear O2 sensor before you spend any more money on sensors. Similar symptoms on my 96 and 98 when the harness fell onto the driveshaft in both cases.

 

[O-Gauge Steamer]

As the gauge cluster is data driven, any of the sensors attached to the PCM can affect the PCM's internal power supply. This will manifest itself in various ways. Wonky displays being just one of them.

Any short (See kastein's suggestion above) in the harness to ground can do this as it will pull the +5 VDc line down.

I had an "opportunity for improvement", i.e. a problem, with my Speedometer a while back. Owing to health issues, the Jeep sat long enough for the battery to loose most of it's charge. When it was cranked, the Speedometer pegged and then stayed there. Had to take the cluster out and move the needle off the stop.

So, now, the Heep gets periodic runs on the battery charger so that does not happen again.

As for the cluster momentarily dropping out and the CEL coming on, the late model XJs are rather famous for the connection at the back of the cluster getting corroded with time. What happens is that the cluster will momentarily lose communication and will reboot.

The symptom for this fault is the CEL comes on then goes back off by itself. Just as it does during the initial start. The cluster runs a diagnostic at power up.

If the CEL will only go off by disconnecting/reconnecting the battery, then this problem does not apply.

If the cluster connection is suspect, it is an easy thing to correct and tons of threads are here documenting it.

 

[ubercurtisb]

Thanks for all the replies, guys. Thought I'd update with a little more specific info, since I had to drive it a bit today.

The Jeep sputters/shakes/kicks when I am trying to cruise at about 45mph, but if I hit the gas or lay off, it'll smooth out. And it seems like it's not as responsive, like it lost some power. The speedometer mainly jumps when I'm starting to accelerate from idle. The check engine light came on on my way to work this morning, and stayed on. Then when I left work, it was on for a couple minutes, then went away, only to come back on once I entered the neighborhood. I'm honestly stumped.

I really appreciate your input, everyone. Just please keep the responses in layman's terms. Explain it like I'm 9 years old. I know some things, but I'm still trying to learn.

Edit: Upon further research, I'm finding the Throttle Position Sensor might be suspect? What say you?

 

[birchlakeXJ]

The check engine light came on on my way to work this morning, and stayed on. Then when I left work, it was on for a couple minutes, then went away, only to come back on once I entered the neighborhood. I'm honestly stumped.

Pull current codes. OBDII is not perfect, but it is awfully darn good at pointing you to the offending circuit.

After pulling codes, it's a good idea to erase the codes and see what returns as you address things.

 

[ubercurtisb]

If I bring it in to a parts store to pull the codes, and the CEL is off, will it still tell you what made it turn on originally?

 

[ubercurtisb]

Sorry to keep bumping this thread, but my problem seems to be getting worse. The engine seems to really be struggling, and the check engine light is blinking when I'm driving it. It stops blinking and just stays lit when I'm at a stop light. I'm afraid I'm a minute away from blowing up my engine.

 

[JTProuhet]

I was having some funky problems with my 98 changes the cps nothing changed, pulled the throttle body and cleaned the Hell out of it and replaced the intake air control valve and my problems disappeared. Clean all your grounds as well. Especially at the little junction on the block below the ignition coil. Good luck

 

[birchlakeXJ]

Sorry to keep bumping this thread, but my problem seems to be getting worse. The engine seems to really be struggling, and the check engine light is blinking when I'm driving it. It stops blinking and just stays lit when I'm at a stop light. I'm afraid I'm a minute away from blowing up my engine.

A flashing check engine light indicates a serious misfire, which if ignored will destroy your catalytic converter.

You gotta retrieve codes!! Use the technology provided to you by your Jeep.