TheSamba.com :: View topic - Any link between Engine temp sensor and Camshaft position sensor

Wed Jan 01, 2025 3:29 pm

I keep getting engine codes for the coolant temp sensor and also the camshaft position sensor.

Last night I swapped in the temp sensor from our bad-transmission EV (and I checked it's ECU, no codes stored at all) and the code persists.

Just curious if maybe there could be something like a shared ground for both sensors? If so, where might it be?

(On my early TDI's, for example, the coolant temp sensor grounds to the engine block, and sends signals to the ECU via that ground through the sensor.)

Thu Jan 02, 2025 2:00 am

I think you're on the right track with the shared ground theory. You should be able to check continuity between the two plugs and from each plug to ground. Rodent damage is also a concern.

Thu Jan 02, 2025 9:11 am

I suppose there could be some kind of shared power instead? Dunno.

Also, I've searched on the camshaft sensor code a couple times, and it seems like there are supposed to be two... I even recall finding a thread where the poster swapped the sensors to see if the trouble followed.

But the code I'm getting doesn't differentiate between it possibly being a number 1 or 2, or front and back or whatever.

VCDS reports:
16725 Camshaft Position sensor (G40)
P0341 - 35-00 - Implausible signal
and
16502 Engine Coolant Temp Sensor (G62)
P0888 - 35-10 - Signal too high - Intermittent

Thu Jan 02, 2025 10:53 am

Implausible signal does seem to fit a ground issue, or at least a corrosion issue at the plug or in the harness.

Thu Jan 02, 2025 7:30 pm

Well...

So I goofed...

I'd seen "you want the green one" in reference to the sensor, so when I went to swap the old sensor out with the one from the FLAPS, I looked up, saw green, and went to work. And was annoyed that the old one had a fully square connector and the new one had one rounded end. That's why I swapped over from the dead van.

I figured it was a deal with the late Eurovans being an update, so there is some old stuff in there, and newer stuff, too. And the catalogs are just in error.

Went in to the FLAPS to return the switch and he went to try to find the right one. We kept running into dead ends, until I saw something about the fan switch as I was looking at pics of parts that matched the one I'd taken off the van...

Turns out, the fan switch is also green! And it is the part that is "old stuff" while the engine switch, is in fact, "new stuff."

Swapped in the switch, and the code seems to have gone away!

Now I just need to figure out the camshaft position sensor, I guess.

Sun Jan 12, 2025 2:23 pm

there is a common ground #18 in the bentley for numerous sensors and the harness. A while back I found this when I had similar issues to yours.

It is located below the exhaust manifold on the passenger side. Hard to get to, hard to tighten.. A stubby 13mm or fine tooth ratchet works.

I chased germlins similar to yours and found it by feel from above. Trace the wire leading down towards the o2 sensor and you will feel it. Prior mechanic went to the trouble of replacing and soldering the connector but never tightened it.. Fixed intermittent issues once tightened up good.

Mon Jan 13, 2025 1:47 pm

rocknroj wrote: there is a common ground #18 in the bentley for numerous sensors and the harness. A while back I found this when I had similar issues to yours.

It is located below the exhaust manifold on the passenger side. Hard to get to, hard to tighten.. A stubby 13mm or fine tooth ratchet works.

I chased germlins similar to yours and found it by feel from above. Trace the wire leading down towards the o2 sensor and you will feel it. Prior mechanic went to the trouble of replacing and soldering the connector but never tightened it.. Fixed intermittent issues once tightened up good.

Thanks for that info! VW has been putting common grounds in weird, difficult spots since at least the invention of the fuel injected type 4 motor!

Mon Jan 13, 2025 4:15 pm

You may want to check the connectors as well. Most of mine went bad over time.. o2 sensor, iac, ect and most recently to the hall sender..... Amazing the thing even ran.. heres' the hall sender before replacement...

Thu Nov 13, 2025 12:47 pm

I have been getting the P0341 code on my 12v AES recently. It comes back quickly after resetting the codes. I ordered a new sensor, arriving today, but I'm 50/50 whether it'll help. I don't have another sensor code coming along with it, so I probably don't have this ground issue, though I should try to find that point passenger side near the exhaust manifold.

So, If the sensor doesn't fix it, what else is there? take the valve cover off to verify the chain hasn't skipped a tooth? That's more invasive than I've ever been into the engine...

Fri Nov 14, 2025 2:51 pm

Okay, new sensor is in, but the code comes back after a few miles of driving. Which means there is something wrong, probably skipped a tooth or something?
If anyone has suggestions on the best way to confirm what's the cause please let me know. I've read the 4-5 threads on P0341 and 16725 codes. Some say let it ride, some say dig into it ASAP.

I should probably have the necessary parts and gaskets in hand before I dig in. So:
Intake manifold gasket
valve cover gasket
upper chain guide (probably cracked)
Anything else While I'm in There?

Fri Nov 14, 2025 3:06 pm

If you installed a cheap cam position sensor, that may be faulty outta the box. BTDT.

If you do tear into the engine to change the chain tensioner(s). Might as well do the chain(s) as well while you have it torn apart. If sprockets are available for your 12V engine consider those too.

Sat Nov 15, 2025 9:42 pm

I'm hoping to only take off the intake and the valve cover to check Cam timing. Not remove the entire side of the engine including the trans.

I actually just drove 300 miles up and down mountains and the car was as adequately powered as always. Driving up grades at 4500rpm in 3rd did give me some unusual short bursts of hesitation: one second of slightly less power and change in engine pitch and then back to normal power for 3-5 seconds. I should have checked the engine timing read out to see if the knock sensor was pulling advance during those moments but I was paying attention to the road. Maybe 89 octane wasn't enough. Or maybe my Cam timing IS off and that's the only symptom.

I'm going to try another sensor, hopefully better, because, like Rusty says, junk parts are a high percentage on Amazon (but it gets here so much faster than Rockauto!)

Fri Nov 21, 2025 12:53 am

I found the following two videos which might help me determine whether my waveforms are correct:
https://youtu.be/ePh3WM1xNfk?si=pUkazfaBAY6sbOou

Thomas exovcds video on good and bad waveforms for 12 valve VR6 timing correlation between Camshaft and crankshaft

He links this other video which does the same thing:

https://youtu.be/1NkNOl8Yzsc?si=EW9E8CkAqhgVWcf2

I do have a better more expensive camshaft position sensor on the way, but the one that's in there is flashing LEDs when I run a back probe from the signal pin to the 12 volts LED and crank it.

Any recommendations for cheapish 2 channel oscilloscopes with record function?

Sat Nov 29, 2025 9:35 am

I futzed with things a lot and then went on a total of 9 more hours of long drives. The code came back once in that time, about 5 hours in. The code used to come back after 5 miles. So I'm back to thinking the sensor is failing/has failed.

Details about futzing: I went back to the old sensor (original, 25 years old) after trying it out of the car, hooked up to a 5v power source. I couldn't get a good signal on either by spinning a Forstner bit in front of sensors. I gave up and tried to do it in the car with a needle back probing the connector at the sensor
I back probed the harness at the sensor to watch the fluctuating voltage on a voltmeter while cranking with the injectors disconnected.
I watched that signal on an LED test light, seeing two long flashes followed by two short when replaying the video in slowmo.
I took out the upper tensioner bolt and checked to see if the tensioner rail/guide still felt intact with my finger. It did feel fine.

I'm back home and have all the parts I ordered in hand. I'm going to bring them on my Thanksgiving trip to California but I probably won't need any of it except the new sensor. I'm not going to tempt fate by replacing it but I'm hopeful it will fix the issue, assuming it isn't also nonfunctional like the cheap Amazon sensor.

My ideas for what's causing the computer to set this fault code:
Bad sensor
Skipped a tooth in the timing chain somewhere
Broken timing chain guides/rails causing the slack in the chain to make the computer see the cam and the crank phasing out of phase, similar to skipping a tooth
Stretched chain causing the same misphasing.

I'll probably change to the new sensor in California when/if the code comes back

Wed Dec 03, 2025 12:06 am

I drove home 700 miles after changing the sensor to the expensive ntk version. The code has not come back. So all my fretting about grenading my engine was for naught. Stupid Amazon sensor. I am still confused about how I partially revived the old sensor but I'll have to read up on how Hall effect sensors work.