camshaft/crankshaft sensors

9998 Views 28 Replies 13 Participants Last post by kloudie1, Jul 28, 2014

mindmess

Discussion Starter · Feb 16, 2012

So I have a 2000 T&C that would throw the code (don't remember #) for the crank/cam sensor bad. It would on occasion throw code and run like crap, till I got to somewhere to diagnose which one. It seemed to reset after a few start cycles. So about a month or so ago it died out when my wife was driving it. Had it towed home, checked code, replaced both. No start. Occasionally does backfire. What to do now. Timing? Flywheel? Don't feel like pissing away $$$ and time to find out it was the other than what I choose to do.

Any suggestions? Tips?

1 - 20 of 29 Posts

dana44

· #2 · Feb 16, 2012

It could be the timing belt or timing chain. The code sets the number of misfires in a given period of time, which can allow it to reset itself after short drives, but you still have to dig into the engine to fingure out what is the real problem.

Which engine is it?

mindmess

Discussion Starter · #3 · Feb 16, 2012

It is the 3.8. I should have put in that the start cycle it made a clunk type sound. Kinda like something popping back in place.?

ImperialCrown

· #4 · Feb 16, 2012

There isn't a fault code for 'bad'. If you can retreive the code, it may give us more to go on. Were the replacement sensors OEM or aftermarket per chance? Do you still have the original sensors to reinstall and start over?
Does the compression sound OK (even among the cylinders) while cranking?
A scan tool diagnostic session may help us decide whether to pursue an electrical or mechanical issue.

mindmess

Discussion Starter · #5 · Feb 17, 2012

Aftermarket sensors. Wanna say 0340? for code. Intermittent loss of cam/crank signal. Still have the old sensors. Will try to listen later, or even see if I can borrow compression tester.
I thought I had seen somewhere before that the flywheel may have cracks between the signal spaces causing issues.

Doug D

· #6 · Feb 17, 2012

Technically the "flywheel" is known as a flexplate in automatics. The 3.3/3.8's have a timing chain - no belt. It's possible the flexplate has cracked jaggedly around the mounting holes allowing the flexplate to move back and forth and may have disrupted the timing enough it won't run. It's sort of a known issue the flexplate can develop cracks like that - my '00 T&C Ltd did this. The solution was to replace the flexplate at a cost of around $600 (mostly labor - the flexplate was only $67). At idle with the AC on mine had a sound like marbles being shaken in a coffee can. The clunk doesn't sound good and could be a clue.

I think there is a cover on the transmission that can be removed that allows some of the flexplate to be viewed.

dana44

· #7 · Feb 17, 2012

In order to check that the timing chain hasn't stretched, grap ahold of the crank pulley and see if you can rock the engine by hand and see if there is play there. Timing chains are pretty durable and have a chain tensioner, so it may be a little bit difficult to check, which could explain the backfire, the difference between the cam and crank timing firing fuel and sparking at odd times is the symptom, backfire the result.

GLHS#0867

· #8 · Feb 17, 2012

aftermarket sensors are not that great in quality anymore. I am sure there is a way to test your new ones. I would guess the new one you put in are bad, most of these new sensors the majority of the metals and general production fitting and such is done in China and then its called "washed" by an American company and called American made products. Try OEM when sensors are replaced, it saved me alot of headaches, by just using OEM parts.

Use OEM parts always.. most times.

ImperialCrown

· #9 · Feb 17, 2012

See if you can borrow or find an OBD II engine code reader/scan tool that can also read engine sensors, try looking at the cam and crank position sensors while cranking.

You should see messages like 'present' and 'in sync' or 'in range'. Any 'lost' or 'out of range' displayed message may be a mechanical issue.

P-0340 NO CAM SIGNAL AT PCM

When Monitored: During engine cranking, after 64 crank position signals.

Set Condition: If no signal from the cam position sensor is present with crank signal, the

code will set.

POSSIBLE CAUSES

ENGINE DOES NOT START

8-VOLT SUPPLY CIRCUIT OPEN

CAMSHAFT SPROCKET OBSERVABLE DEFECT

CMP SENSOR GROUND CIRCUIT OPEN

CMP SENSOR WIRING HARNESS OBSERVABLE DEFECT

DISTRIBUTOR AND PULSE RING OBSERVABLE DEFECT

CAMSHAFT TARGET MAGNET OBSERVABLE DEFECT

CMP SENSOR DEFECTIVE

CMP SENSOR CONNECTOR OBSERVABLE DEFECT

PCM DEFECTIVE

CMP SENSOR SIGNAL CIRCUIT OPEN

CMP SENSOR SIGNAL CIRCUIT SHORTED TO 8-VOLT SUPPLY

CMP SENSOR SIGNAL CIRCUIT SHORTED TO GROUND

CMP SENSOR SIGNAL CIRCUIT SHORTED TO SENSOR GROUND

TEST ACTION APPLICABILITY

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valiant67

· #10 · Feb 17, 2012

Also, the crank sensor is very sensitive to the mounting depth. There should have been a space on a new sensor to set the proper gap. Improper gap will keep it from starting.

mindmess

Discussion Starter · #11 · Aug 23, 2012

Well I finally had schedules line up with my buddy to work on this issue. We hooked car up to scanner and ran tests. We found all tests were good except for CKP state. When we would ground sensor wire, there was no change. The CMP state would show present.
Both power leads were 8.9v. Ohms were 5. Ground CMP signal would cause fuel pump relay to click.
So the best guess/idea is that the PCM is toastered. Can pick one up a reman one from a boneyard nearby for $100.
Am I correct in this assumption? Go with replace PCM?

mindmess

Discussion Starter · #12 · Sep 7, 2012

Got reman PCM and installed. Now tests come up good and can hear relay clicking when grounding. STILL won't start. Pulled sensors to check them, and they both have the paper on them. Removed paper and tried again, no go. All it does is make one attempt to start and then the starter just cranks away.
I guess we will separate the tranny and motor and try the flexplate as that seems to be a common well known culprit.
Any thoughts or other suggestions?

John Wood

· #13 · Sep 7, 2012

mindmess said:
Got reman PCM and installed. Now tests come up good and can hear relay clicking when grounding. STILL won't start. Pulled sensors to check them, and they both have the paper on them. Removed paper and tried again, no go. All it does is make one attempt to start and then the starter just cranks away.
I guess we will separate the tranny and motor and try the flexplate as that seems to be a common well known culprit.
Any thoughts or other suggestions?

The paper on the sensor is usually swept away when the vehicle is cranked. It almost sounds like the crank position sensor depth was not set correctly. If you still have the paper spacer, re-attach it with light adhesive and reinstall the crank position sensor depth so that it just bottoms out against the flex plate. Then when you crank the engine, the paper should come off and leave a gap of about 1/64 of an inch which would be enough to not make contact with the plate, but provide enough of a gap for the sensor to work.

I assume you still get the code, even with the new PCM.

ImperialCrown

· #14 · Sep 7, 2012

If the cam and crank position sensor signal remained 'present' on the scan tool display, then I think that your flexplate/timing chain should be OK.
I agree that the paper spacer should set the sensor depth and be swept away after the vehicle is started.
The flexplate might warrant a look-see to rule out concentric/radial cracks for peace of mind.
Any recent history on the transaxle being removed?

mindmess

Discussion Starter · #15 · Sep 7, 2012

I have the 1391 code still/again.
I have never done anything to the transaxles and don't recall there being anything about them in the paperwork I have from when I bought the vehicle.

Oklahoma Wolf

· #16 · Sep 9, 2012

Check for bad solder joints in the cluster, and/or a melted connector behind the HVAC controls.

These are two very common problem areas with these vans, especially as they get older, and will cause intermittent no start conditions like this (among other things). It's gotten to the point I would look at these two areas first, regardless of the codes being thrown.

Also, check to see if the PCM connector can be wiggled back and forth. If so, it's loose. Sometimes the bolts that hold the connector together are too long, and won't allow a secure connection even when tight. Cut a little bit off the end of the bolt if yours is loose. I successfully fixed a similar issue on my 1991 Fifth parts car this way. It threw constant crank sensor codes, but replacing it did not fix the problem. It was the PCM connector being loose that caused it.

Check for the cluster and HVAC issues for sure, though.

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mindmess

Discussion Starter · #17 · Sep 18, 2012

Did not see any wire issues. Tore it all apart and surprise surprise, cracked flexplate. Also whomever owned it before me had the right driveshaft nut welded on.(needed to pull for a ripped cv boot) Will post pics later.

Am waiting on a replacement flexplate, again. First one I got looked like someone couldn't get it to line up and started drilling holes in it. Then returned it. ARRRGH

Question I have though is, is there an alignment dowel on the flexplate or certain way it needs to go on? Or does it not matter due to the ring spaces for the sensor to read that the pcm does it all.

John Wood

· #18 · Sep 18, 2012

There is only 1 way it will go on. The bolt pattern spacing is very slightly different, even though it is not apparent. There should be a supporting/bolt locking ring that goes on the back of the plate. You can match mark that to the plate and also use it to determine orientation for the correct bolt hole pattern.

Aldergrove

· #19 · Oct 2, 2012

Does anyone know the value of the gap for the CPS. Prior to reading this thread I asked a transmission tech who suggested .040`` which is considerably larger than Johns 1/64`` or .016``

valiant67 said:
Also, the crank sensor is very sensitive to the mounting depth. There should have been a space on a new sensor to set the proper gap. Improper gap will keep it from starting.

Aldergrove

· #20 · Oct 2, 2012

I never knew that the connector behind the HVAC controls or a bad solder joint in the instrument panel cluster would cause a no start!!!!

Oklahoma Wolf said:
Check for bad solder joints in the cluster, and/or a melted connector behind the HVAC controls.

These are two very common problem areas with these vans, especially as they get older, and will cause intermittent no start conditions like this (among other things). It's gotten to the point I would look at these two areas first, regardless of the codes being thrown.

Also, check to see if the PCM connector can be wiggled back and forth. If so, it's loose. Sometimes the bolts that hold the connector together are too long, and won't allow a secure connection even when tight. Cut a little bit off the end of the bolt if yours is loose. I successfully fixed a similar issue on my 1991 Fifth parts car this way. It threw constant crank sensor codes, but replacing it did not fix the problem. It was the PCM connector being loose that caused it.

Check for the cluster and HVAC issues for sure, though.

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