My Jeep stalled and will not restart. Turns over strong but will not fire. The gas and the alternator dash indicators do not work when I turn the key.

I had received a check engine light. just before stalling I had it scanned at AutoZone. One of the error codes was p0320. Also had an O2 circuit high voltage.

In previous weeks the RPM's would suddenly drop to zero and pop back up

I checked and I do not have a spark.

I have disconnected the CPS but the dash indicators still do not work when I turn the key.

I tested the CPS with a voltmeter. I'm a bit confused about what it shows and what it's supposed to show. I am not sure what two prongs I'm supposed to test. I tested one and two and two and three. Neither test took it down to zero resistance but was not at infinite resistance either.

I was expecting the dash indicators to work again when I disconnected so I am not sure if it is the CPS.

Unless somebody has another idea I am planning on changing the CPS as a first step.

Thanks for any ideas or insight.

 

It sounds like it is the crankshaft position sensor to me. The code points to it. It cranks over strong, but will not fire off the engine. You have no spark. It sounds like a bad CPS.

You can hook up a diagnostic scan tool. One of the settings is to measure the engine speed in RPMs. The scanner gets this information directly from the crank sensor. Set up the scanner to read the engine RPM and crank the engine. The scanner should read between 100 - 500 RPMs. A zero reading indicates a completely failed CPS.

 

I'm not aware of any connection between the CPS and the dash gauges. That's probably coincidence, OR, you have a complletely different problem.

The CPS can be tested. I'd start there, and if it tests bad, replace it. Then look for your gauge problem.

 

I remember when I was researching why my '00 XJ was stalling when reaching operating temperature.
When researching the CPS I came across all sorts of things that could help identify it being the problem.
Weird gauge crap, no bus signal, CEL's, and pending CEL's.
I had none of that. Turned out it was the CPS.
Also it has been my experience that if the CPS is suffering from thermal failure that it will test OK.
Assuming I did it right following the Bleepin' Jeep video. LOL.

 

All signs indicated it wasn't the CPS. Ended up the O2 sensor wires shorted out on drive shaft and blew out the ASD fuse.

 

That's excellent! Thanks for the update.

It makes complete sense. The ASD relay provides power for the vehicle’s oxygen sensor heater circuit as well as function as an automatic shut down switch that will shut off the fuel and ignition systems when the computer detects that the engine is no longer running (ie: during an accident).

The ASD is responsible for providing switched 12Volt power to the injectors and ignition coil, allowing them to provide fuel and produce spark. Since the ASD is also used to provide power in order to heat up the O2 sensors, the short here in the O2 sensor wiring blew its fuse. The blown fuse prevented the ASD from being able to supply power to the ignition coil = no spark.

Did you end up testing the CPS? It tested normal.. and then you found the blown ASD relay fuse? You traced this circuit, and it lead you to finding the short?

 

Did some testing with multimeter on the CPS. It was a bit confusing and nothing indicated for sure that it was the CPS. I was ready the change anyways.

My son in law found the blown fuse and we went from there. I read somewhere that the O2 was on that circuit..

It was pretty cool figuring it out. Hopefully it will help someone else out.

Thanks

 

It is definitely helpful!

At minimum, I will be filing it somewhere in the back of my head for in case I have a similar no-start problem with either my Jeeps in the future. I will know this now, to possibly help someone else that comes here to this site with a non starting, no spark, good testing CPS problem too.

I really appreciate the updating! I fear no-start problems while I am out on the road. I have been trying to learn and teach myself all of the different reasons and possibilities for having this problem in these Jeeps. To be able to fix them, and any other possible issue that may arise when far from home...

You were very helpful to me. Thanks again!

 

I have a 96 jeep grand cherokee laredo with a 4.0l I have the same issue I changed the cps out and my guages were not working when I turned the key on so I turned the key off and back on the gauges would finally come on and it started so I let it run for a little bit then killed went to start it again and no gauges then they turned back on and I was not getting any voltage to my coil test with Volt meter so I I turned the key off and back on then the gauges come and it started then did it all over again I need some this damn thing is driving me nuts thank you

 

It sounds like you need to figure out why there is no voltage at the ignition coil. What would cause that? Maybe it could be a faulty ignition coil itself? I think they are inexpensive to replace? I think it is recommended to replace older ignition coils as a normal maintinance item?

The crank sensor allows the PCM to see greater than about 200 RPMs, to use as an indicator which allows the ignition system components to produce spark.. The CPS sensor it would be a good component to verify as operating correctly. Make sure the wires leading to it are proper. Test them and the sensor to be sure.

I also think checking all of the fuses is a good idea. The fuel pump and auto shut-down relays would be good to verify as operating correctly. I am not sure what other relays may be involved in powering up the ignition system components?

What can cause the ignition coil to not recieve power, or show voltage? Maybe the grounds involved with the coil? Maybe the ignition switch?

I have read it being possible for the connections at the ECU-PCM to cause similar type of problems. I saw some people were recommending to undo the PCM connectors and clean them with an electrical contact spray cleaner. Some of the people were recommending to use zip-ties to hold the PCM connectors tightly in place. Doing these two things resolved various different problems.

I would try to ignore the gauges. Unless it was a CEL or dignostic trouble code. The gauges issue does indicate this as being an electrical problem though.