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crankshaft/camshaft position sensor issues

Q

quinnt

NAXJA Forum User
Location
Palmer, Ma/Rindge, NH
So I've read and searched and not getting any answers I need.

I parked my jeep for 5 minutes then when I tried to restart it it wouldnt. Code that had come on 2 hours prior said missfire on cylinder 3(I think this is an old uncleared code) and Crankshaft Position Sensor. Repalced the CPS and it still wouldn't start. A mechanic said it could also be the Camshaft Position Sensor. I exchanged parts and am now trying to get the old sensor off but am running into trouble getting the old rusted bolts out. Before I end up breaking one of the bolts, could this be a problem with the Camshaft Sensor thats tripping the Crankshaft Sensors Code?

2001 XJ, 4.0, auto

Thanks
 
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Crank and cam position sensor throw the same code - I think it is P1391. So it could be either one.

Make sure that the CPS you just put on is working correctly. I just went through this last week and the replacement CPS from Autozone was just as bad as the one I pulled from the tranny. When I replaced it with an OEM unit ($135!) it solved the problem.

You can do a check of the CPS by looking at post #6 in this thread: http://www.naxja.org/forum/showthread.php?t=969083
 
Thanks, I'll try to get a hold of a multimeter tomorrow.

Thing is my gauges work correctly, there's gas in the fuel rail, and it's not getting spark(sprayed starting fluid in and no luck). In the past I have had it where I get no bus in the odometer and all my gauges drop. It's not the NSS

Thanks for your response
 
Yes, some of the codes for the crank sensor are used interchangeably with the cam sensor.

Normally, a failing cam sensor will allow spark, but I have seen them fail in a certain way that inhibit spark. Cam sensors can be tested with a meter and a manual.

Be sure to squirt a dose of penetrating lubricant around any rusted bolts and let it work for a while before trying to loosen. Then tap with a hammer a bit.

If you have a NO BUS and the engine won't run, it usually is the crank sensor shorting out. (theoretically if can be anything along the 5 volt bus shorting, but the crank sensor is the one that is most prone to this type of failure)

If you have a NO BUS and the engine runs fine, the problem is usually a connection issue in the cluster. Removing cluster, cleaning cluster connection with electrical contact cleaner and applying dielectric grease to the connector usually resolves.

You can also try swapping the ASD (autoshutdown) relay in the Power Distribution Center (black box for fuses and relays) with another one. These relays are of the same part number so they can be safely swapped for troubleshooting.
 
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I tried swapping the relays around. Currently my odometer is reading the mileage not NO BUS. I'll try to get the Cam sensor tested/swapped out tonight and let everyone know how it goes.
 
odo reading no bus makes this sound like a crank position sensor issue to me.
 
Thats what I thought too but it hasn't said NO BUS in a while and the crank sensor I put in didn't change anything.

When I took the cam sensor off today all the junk inside was broken, so that's clearly and issue. I put the new one on and it still won't start. Is it possible that both the crank and the cam sensor went bad at the same time? If thats the case then the one I got from the store must have been bad too. There was a few hours and starts and stops between when the CEL first came one and when the jeep wouldn't start again.
 
Well the 2nd new crank sensor didn't work. All the wires look good, its not any of the relays. Tried resetting the computer didn't change anything and CEL is still on. Checked all the fuses. Theres fuel in the rail, starting fluid didn't get get it to start. I'm trying to get a hold of a multimeter. Where is the connection I check for the cam sensor? I know which one to check for the crank sensor. What are they suppose to read at?

I feel like I'm running out of options here.hasta
 
Ok, so you have replaced the damaged synch sensor in the distributor--correct?

It is quite possible you have flooded then engine trying to start it.

Hold the accelerator to the floor, then crank the engine over. Holding the accelerator to the floor puts the PCM in "clear flood" mode--it cuts off the firing pulse to the injectors allowing the engine to clear itself of the flooding. Give that a try.
 
quinnt said:
I don't think I have a synch sensor as I have a 2001 cherokee. I did replace the damaged camshaft position sensor. There's still a CEL after resetting the computer.
Click to expand...

Synch is the Cam sensor. Is the distributor bad? bearing, side to side play? Why, how did the Cam sensor get damaged?
 
no distributor on a 2001

The Camshaft Position Sensor (CMP) on the 4.0L 6–cylinder engine is bolted to the top of the oil pump drive shaft assembly. The sensor and drive shaft assembly is located on the right side of the engine near the oil filter.​
 
McQue said:
no distributor on a 2001

The Camshaft Position Sensor (CMP) on the 4.0L 6–cylinder engine is bolted to the top of the oil pump drive shaft assembly. The sensor and drive shaft assembly is located on the right side of the engine near the oil filter.​
Click to expand...

Interesting. Now that I am up to speed, I ask the OP again, what damaged the old one?
 
I'm not sure what damaged the old one. Externally it looked good but when I took it off all the internals were sitting on top of the oil pump assembly. I took care to clean them out without moving the half circle thing and anything else in there.
 
the_weirdo said:
Crank and cam position sensor throw the same code - I think it is P1391. So it could be either one.

Make sure that the CPS you just put on is working correctly. I just went through this last week and the replacement CPS from Autozone was just as bad as the one I pulled from the tranny. When I replaced it with an OEM unit ($135!) it solved the problem.

You can do a check of the CPS by looking at post #6 in this thread: http://www.naxja.org/forum/showthread.php?t=969083
Click to expand...
I've never had a sensor failure on my 99 with OBDII, but it's interesting that it throws the same code, because OBDI has a code for each.
 
Matthew Currie said:
I've never had a sensor failure on my 99 with OBDII, but it's interesting that it throws the same code, because OBDI has a code for each.
Click to expand...

Well... P1391 isn't quite the whole range of CKP/CMP codes (for a 2000, at least).

P0219: Crankshaft Position Sensor Overspeed Signal
P0320: No RPM Signal to PCM (Crankshaft Position Sensor Signal to JTEC)
P0336: Crankshaft Position (CKP) Sensor Signal
P0340: No Cam Signal At PCM
P0341: Camshaft Position (CMP) Sensor Signal
P1390: Timing Chain Skipped 1 Tooth or More (CMP/CKP signals out of sync)
P1391: Intermittent Loss of CMP or CKP
P1690: Fuel Injection Pump CKP Sensor Does Not Agree With ECM CKP Sensor

I think that's all of them, but may have missed one or two.

FWIW, when my oil pump drive gear disintegrated the codes that were thrown were P1390 and P1391. Not sure how P1391 came into play given that there was no damage to the wiring, but I suppose it's possible that internal damage to the cam sensor could have been responsible.
 
quinnt said:
So what can I test to try to track down what it is? I have a multimeter.
Click to expand...

Since the CPS has already been done and you've got the cam sensor in hand, go ahead and swap it out. Once that's done, clear the codes and see what happens, but this will likely take care of it.

If it's still bad after the swap, I'd be inclined to suspect the CPS, especially if it came from Autozone/Advance Auto/Pep Boys/O'Reilly's, etc. Don't know what it is, but the quality of sensors for the 4.0 that those places are carrying seems to have plummeted across the board in the last 2-3 years or so - not that it was all that great to begin with.
 
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casm said:
Well... P1391 isn't quite the whole range of CKP/CMP codes (for a 2000, at least).

P0219: Crankshaft Position Sensor Overspeed Signal
P0320: No RPM Signal to PCM (Crankshaft Position Sensor Signal to JTEC)
P0336: Crankshaft Position (CKP) Sensor Signal
P0340: No Cam Signal At PCM
P0341: Camshaft Position (CMP) Sensor Signal
P1390: Timing Chain Skipped 1 Tooth or More (CMP/CKP signals out of sync)
P1391: Intermittent Loss of CMP or CKP
P1690: Fuel Injection Pump CKP Sensor Does Not Agree With ECM CKP Sensor

I think that's all of them, but may have missed one or two.

FWIW, when my oil pump drive gear disintegrated the codes that were thrown were P1390 and P1391. Not sure how P1391 came into play given that there was no damage to the wiring, but I suppose it's possible that internal damage to the cam sensor could have been responsible.
Click to expand...
My bet is that it saw the p1391 while the gear was partially stripped and the sensor was being turned occasionally as the partial remaining teeth hit the cam.
The p1690 is probably diesel only.
 
Like I said previously, both sensors are swapped and the computer was reset and the code came back. I don't really wanna drop another 130 on a CPS unless I know it will fix it.
 
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