Could use a little help-cam sensor, (or at least I thought it was)

invader

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Mar 12, 2008
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santa cruz area, ca
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2006 Jetta TDI
(SOLVED!) Could use a little help-cam sensor, (or at least I thought it was)

Sorry, this post will be a little long.:rolleyes:

So last Tuesday morning I left for work at 5:00am
Got about 4 miles from home and the car starts cutting out and running like crap.
I get to a safe spot to pull over and stop and the car dies.
So I go to start it up again and it runs for about a minute, but it seems like its running on 1 or 2 cylinder and then dies. again

So I sit there for a couple minutes, gather my thoughts and then figure its time to try to get a tow truck.

Then I decide to try starting it one more time and it fires up and seems to be running normal now. Not missing any more and running smoothly. So I put it in gear and start to go. It seems fine for about 50 feet and then it starts running like crap again and as soon as I pull over, it dies and now it will not start again at all. So I get it towed home and drive my truck to work.

Forgot to grab my laptop, which has the VCDS on it, from work Tuesday night so I just did a couple initial checks when I got home.
Looked at the timing belt. Looks fine. No fraying and seems nice and tight. Checked to make sure the fuel pump in the tank is working. Also pulled the valve cover. Cam looks good no wear or chamfering on the lobes and the tappets look good from what I could tell.

So Wednesday, I brought home my computer and did the scan. came up with P3008, cam sensor out of range. Researching this site and some other ones, I found that you can unplug the sensor and it should start. Sure enough, I unplugged it and it started right up. Seemed to be running normal, idling smooth. So I decide to see if it will drive with the cam sensor unplugged. Drove normal for about 100 feet up the road and it started cutting out again. Same thing, felt like it was running on 1 or 2 cylinders. I pulled over and it died. I fired it back up and it was running like crap. I turned it off again, waited about a minute and fired it up again. This time running normal again, so I backed back up and back into my garage.

So I went ahead and ordered a new cam sensor. Didn't have a chance to install it until today. With the new sensor in, exactly the same symptoms.
Wont start with it plugged in and starts right up with it unplugged. Not going to try to dive it again.

One other thing. I checked the voltage and continuity on all three wires on the connector going to the sensor. I have 5 volt on pin 1, (power to the sensor). Pin 3 , (ground), is less than 1 ohm to ground and pin 2 is some number of K ohms to ground. So it looks like the wiring is OK.

So any ideas would be great.

I have a hard time believing that the timing belt has slipped a tooth since it starts and appears to idle normal with the sensor un plugged?

Hopefully someone has something else to try.

Thanks
 
Last edited:

oilhammer

Certified Volkswagen Nut & Vendor
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Dec 11, 2001
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outside St Louis, MO
TDI
There are just too many to list....
Engine harness. I would place an ohm meter on the three wires from the CMP sensor back to the ECU plug, and watch the value while you wiggle around on the harness, in particular down by the starter area.

Be careful when back probing the ECU connector, as you need a very small pin otherwise you can mangle the female connector. There are a pair of tamper proof breakaway bolts on a bracket that keep the connector and ECU together, that will need to be cut off. I grind slots into them and use a big flatblade screwdriver to remove them.

They are easier to get at with the removable portion of the firewall out of the way (easy).
 

invader

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Joined
Mar 12, 2008
Location
santa cruz area, ca
TDI
2006 Jetta TDI
Engine harness. I would place an ohm meter on the three wires from the CMP sensor back to the ECU plug, and watch the value while you wiggle around on the harness, in particular down by the starter area.
Be careful when back probing the ECU connector, as you need a very small pin otherwise you can mangle the female connector. There are a pair of tamper proof breakaway bolts on a bracket that keep the connector and ECU together, that will need to be cut off. I grind slots into them and use a big flatblade screwdriver to remove them.
They are easier to get at with the removable portion of the firewall out of the way (easy).
Thanks for the response Oilhammer. The ECU was easy for me to get out. I’ve had it out before.
I checked continuity between all three wires at the sensor connector and the respective pins on the connector at the ECU. All three wires show good continuity, (0-.1 ohms), from one end to the other. And I did as you said and wiggled the wire harness all the way from one end to the other.
I also checked continuity in all combinations befween the three wires. No continuity between any of the three wires.
Any other thoughts?
 

Vince Waldon

Top Post Dawg
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Apr 25, 2009
Location
Edmonton AB Canada
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2001 ALH Jetta, 2003 ALH Wagon, 2005 BEW Wagon
It's (remotely) possible one of the wires is worn thru somewhere and touching ground, so you could also see if you have continuity between any of the three wires and ground itself.

Otherwise it sounds like you've exhausted the possibilities in terms of testing that specific set of wires.
 

Bob S.

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Aug 17, 2006
Location
Central MD.
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A B4V, some ALHs & BRMs
Open up & inspect the engine harness loom in the area of the clamp that holds the harness to the frame just above the starter. In addition to the harness jiggle test, spray some water into the harness in the same area. If it is harness chafe, water introduced will probably confirm prior to the visual inspection.
 

invader

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Joined
Mar 12, 2008
Location
santa cruz area, ca
TDI
2006 Jetta TDI
I will take a closer look at the harness tonight.

I there any possible way the timing belt could have jumped a tooth since it will run apparently normal with the sensor unplugged?

Trying to decide it its worth the work to line it up on TDC and check the timing marks.
 

Bob S.

Top Post Dawg
Joined
Aug 17, 2006
Location
Central MD.
TDI
A B4V, some ALHs & BRMs
Per Dan G's work/testing, the BRM will start & run on either the CkPS or CmPS. I do not know the effects at start up if there is no, or corrupted, CmPS signal. When there is no/corrupted CkPS input, there is a very slight delay in start & Tach needle registering. My memory is that it is about 10 sec. cranking time during which there was no start or tach signal. After about 10 sec, the tach would register & the engine would almost immediately start. My understanding is that the ECU wants the CkPS input, but in the absence of that will default to & use the CmPS input. I do not know what will occur in the absence of the CmPS & if you will see that slight delay. As you test & work on this, please let us know.

Based upon the number of harness problems in the BRM, my opinion is that you have a higher probability of a harness chafe issue vice a jumped tooth. Please know, that the harness chafe can occur a several locations along the loom. The clamp area immediately above the starter is the most common spot.

Good luck with it.
 

invader

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Location
santa cruz area, ca
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2006 Jetta TDI
Found the problem. It wasn't the wire harness.
It was the timing belt. Found a section on the belt where about 5 or 6 ribs are sheared off. I'm sure it has slipped a little.

So I guess the motor can still run, sounding and felling normal, with a slipped belt.

Question is now have I crashed the valves into the cylinders?

Also, When I go in to changed the belt, how do I know which way to rotate the cam/crank to line then back up to the correct position to install the new belt?
 

banshee365

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Nov 4, 2012
Location
FL
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06 Jetta
Found the problem. It wasn't the wire harness.
It was the timing belt. Found a section on the belt where about 5 or 6 ribs are sheared off. I'm sure it has slipped a little.

So I guess the motor can still run, sounding and felling normal, with a slipped belt.

Question is now have I crashed the valves into the cylinders?

Also, When I go in to changed the belt, how do I know which way to rotate the cam/crank to line then back up to the correct position to install the new belt?
You’ll want to drop the $30ish on a set of timing belt tools to do the job. It’s the only right way to do it. You sound very inexperienced with this sort of repair so I look over as many TDI timing belt jobs as you can, specifically on the BRM. It’s a rather easy timing belt but, as with all timing belts, it needs to be dead nuts on. You really need a good belt on the car to test for valve damage. You could remove the belt, lock the crank at 90 degrees opposite direction of rotation and turn the cam manually with the valve cover off and do a leak down test on each cylinder when the respective cylinders valves are both closed. Or you could install a new timing belt and attempt the start from there. I would probably install the new belt, unplug the injector harness at the head, turn the engine over without firing the injectors and listen for an uneven crank. If it sounds smooth I would plug the harness back in and start it and see how it runs.
 

invader

Veteran Member
Joined
Mar 12, 2008
Location
santa cruz area, ca
TDI
2006 Jetta TDI
You’ll want to drop the $30ish on a set of timing belt tools to do the job. It’s the only right way to do it. You sound very inexperienced with this sort of repair so I look over as many TDI timing belt jobs as you can, specifically on the BRM. It’s a rather easy timing belt but, as with all timing belts, it needs to be dead nuts on. You really need a good belt on the car to test for valve damage. You could remove the belt, lock the crank at 90 degrees opposite direction of rotation and turn the cam manually with the valve cover off and do a leak down test on each cylinder when the respective cylinders valves are both closed. Or you could install a new timing belt and attempt the start from there. I would probably install the new belt, unplug the injector harness at the head, turn the engine over without firing the injectors and listen for an uneven crank. If it sounds smooth I would plug the harness back in and start it and see how it runs.
Thanks for the tips.

I have the tool set for changing the belt.
I changed it last time. I was planning to do it within the next few months as I have a little over 90k miles on this belt.

My concern is the fact that it has slipped and the cam and crank will no longer be in the correct position with respect to each other.

Again, thanks for the tips .
 
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