OtterGreenhat

I'll give you the lowdown:

I have an '01 XJ

For about a year, my dash cluster was occasionally "shorting" out. Tach and Speedometer would drop to 0 and I'd have to give the dash a whack to "remedy" the issue.
Recently, the airbag light has been jumping on for no reason then going off.
The whack seemed to fix that issue as well.

Replaced Ignition Switch (was failing) - Car drove fine for weeks
Went for a brief drive one night, came back to start my Jeep 2 hours later and the engine almost started, then went into this endless cranking. Over/over/over/over, no start. "no buS" reading on the odometer accompanied by a steady check engine light.

The code reader displays "FAIL" after trying to read the computer for 20 seconds.

I know the bus is looking for several signals upon startup to determine if it should fire the injectors (or even the fuel pump, in some cases).

I've been told and have read that the CKP sensor is probably to blame. I'm skeptical only because I'm having trouble testing it since diagrams posted regarding my model's pigtail seem to be a bit off.

Here is the diagram from the Manual:


I have a multimeter and I need to know how to test THIS particular plug with an ohmmeter.

Also, if after reading my post you may think it's something ENTIRELY different than what I'm currently testing, then, by all means, feel free to enlighten me because at this point I'm completely stumped.

I'm a college student and have a limited wallet, hence the reason I haven't just gone to the dealer. I love my XJ though and I know I can fix this with the right info. If anyone can help me out that'd be killer.

OtterGreenhat

Nothing? No one can even give me some info regarding properly testing the crank sensor? I know there's a thread out there that explains the way to test it but the diagram is a little misleading when compared to the one in the manual.

duncan0668

I looked in the factory service manual and could not find anything on testing the Crank Position Sensor. I sends a pulse to the PCM to set timing and fuel injector timing. I does say the engine will not start if it don't see the CPS.

OtterGreenhat

Normally if the CPK is failing it throws a code, but mine isn't. There's supposed to be a way to test the sensor itself at the plug with an ohmmeter but I'm getting some inconsistent results because the suggested test from this thread doesn't seem to apply to the pigtail on my '01's CPK sensor pigtail.

Since I'm testing continuity it shouldn't matter where the positive and negative probes are place, one would think. But I'm getting different readings depending on the arrangement. It's very frustrating.

OtterGreenhat

Bump.

C'mon, someone's gotta have an idea, here.

BrianV

Im in the same boat as you with a 98....

I was able to unplug the CPS and let it sit for a few then plug it back in. The truck would start for days after that but now.... nothing.

My gauges wont come up either unless I unplug it.

zman32006

you take your ohm meter and put it on the two metal pins on the connector and you should get a reading anywhere from 200-275 anything else and its bad.

heres a link for testing it http://www.lunghd.com/Tech_Articles/...iagnostics.htm

50-c

Otter,

The vehicle died after starting normally on Sunday evening.

I have the same plug as you do on my 2000 grand cherokee 4.0. I could not get any resistance readings across any combination of the three prongs inside the crank sensor plug. I never received anything but a clean OBD II scan. The shrader valve on the fuel rail was pressurised. I pulled off the coil rail and a spark plug and determined by holding the rail and the spark plug up against the conveniently placed battery grounding terminal that the the grounded spark plug was not firing so all things pointed to the crank sensor.

What a *itch getting the thing out. I tied a 48" string to the end of the wire where the plug was so that I could pull the wire back into position. I ended up putting a floor jack under the tranny mount and undid the 8 crossmember bolts and lowered the tranny as far as the exhaust would let it. This enabled me to get my 11mm socket on the end of about 18 inches of extensions to loosen the single bolt that holds the sensor and the wire guard in place. I had to use a pair of channel locks to grab the sensor to pull it out as my arm was not long enough. I cursed and swore at the engineer who allowed this design to go forward. I also removed the rubber between the plastic on top of the throttle body and the air cleaner so as not to stress this as I lowered the rear of the motor.

I bought a new CPS at NAPA PN CSS618 for $48 including the sales tax. I tried Jeep but the Jeep dealer said that there are 2122 on back order so it is obvious to me that Obama Motors intends to take all these vehicles off of the road by allowing all the crank sensors to go belly up without a replacement part being available. Anyway, on the new one, I measured the resistance and pins 1 to 2 were open but pins 2 to 3 showed 725 ohms as compared to the original which was open across both 1 to 2 and 2 to 3. So it appeared conclusive that the crank position sensor was to blame.

She fired right up after the change out. BTW, the cardboard/paper shim on the end of the sensor is to be 0.030 inch so if it needs to go in and out a few times, you know what thickness to replace it with. The sensor with the cardboard on the end is to be pressed into the hole in the bell housing so it goes in as far as it can. The paper will chear off when the engine is started....

Back in 1986, I was the proud owner of a brand new 1986 comanche. Only a week old, it died on me in NYC as I was driving through. Under the warranty, they had to come rescue me which took about 8 hours. It was the crank sensor.....and it was only a week old..... To add insult to injury, the SOBs dropped the hood down to shut it when there were still some tools on top of the motor so they dinged the hood pretty bad right in the middle, then denied it. In addition, they stole the cigarette lighter and the cap for the power steering. Of course, PS fluid blew out all over as I drove it home. I will never buy new again nor will I ever let anybody ever work on my vehicles.....

Let me know.....

Chris

xj2000

My 2000 XJ engine with 150k mi quit starting two days ago without any warning. The starter turned fine but the engine wouldn't fire up and CPS was the culprit. The XJ fired right up with a new CPS. As expected, it was a *itch replacing it. I used a 11mm socket on three 3/8" drive extensions (6", 3", and 10") and an elbow. I approached it from behind the left front wheel, from the ground, and was able to loosen and tighten the two bolts. I got in from top to unscrew the bolts with my fingers and replace the CPS. My XJ is OEM and I did the job without jacking it up. By the way, there was no OBD2 DTC code for this CPS failure.

xj2000

This is a follow up to my post from two months ago. My XJ ran ok when I installed Master Pro CPS, PN 2-96126, but it occasionally was not firing properly, rough idling. I finally changed the CPS today to Echlin brand from NAPA, pn CSS638, and that eliminated the problem completely. It is now running much smoother. Has anyone had problem with the Master Pro brand CPS from O'Reilly/Schucks? I'm going to try returning it.

tjwalker

Some aftermarket crank sensors have been known to be flaky, and even if they do
work out of the box, the longevity isn't there. Interesting about the backorder of crank
sensors at the dealer......

If you do see a NO BUS and along with that, you have a NO START, the most common cause is the crankshaft position sensor shorting. Theoretically, any of the 5 volt engine management sensors along this bus could do this, but the crank sensor by far is the one that does it the most.

Here is what I do (first anyways) when I work on this fault. I unplug the crank sensor circuit, either at the bellhousing where the sensor is located, or at the plug inside of the engine bay near the firewall/#6 injector.

IF when unplugging the crank sensor, (you have now taken that sensor off of the bus) the NO BUS message disappears, you have proof positive that the crank sensor is shorted and bringing the computer bus down.

The crank sensor is probably the #1 or #2 most common sensor failure on the 4.0. Without that critical input signal from the crank sensor to the computer, you will not have spark and you will not have fuel going TO the fuel injectors (even though the fuel pump may work and you have fuel pressure at the fuel rail).

xj2000

Thanks for the information. I made a note for future reference.

xj2000

[QUOTE=tjwalker;748661]Some aftermarket crank sensors have been known to be flaky, and even if they do
work out of the box, the longevity isn't there. Interesting about the backorder of crank
sensors at the dealer......

SweetLou

I don't think your dash was "Shorting" out, the plug-ins on the gauge setup on these jeeps can be weird. I have a 98, and i recall years ago a buddy of mine had a 98 jeep, and the dash would go out. Problem is there are 2 plugs for the dash, and both are solid mounted to a bracket, and the dash kinda "Slides" into place. Going over bumps and what not can jar the dash slightly loose from one of the plugs and heance the airbag light goes on and parts of the dash such as the speedo will stop working, if I remember right, that would be the right side plug. Just take your fingers and push your dash back in. May not last long, but it can do the trick. I pulled my whole dash apart to see if there was something else that could be done to lock them in place, but I really didn't see a viable solution.