1.9 TDi Camshaft Position Sensor "No signal & implausible signal"

[matthew_grey2k]

Hi there,

Just wondering if anyone has experienced/resolved the same issue as the one I am having right now. I've been experiencing a long cranking issue (notably when staring the vehicle hot) for a couple of weeks now and when scanned for faults - unfortunately not with VCDS, just a basic Carista mobile app - I was getting a "P300700 - Camshaft Position sensor: No signal" fault. Other than being a bit slow to start the van runs perfectly. No EML, no limp mode or rough running and no loss of fuel economy. The timing belt was changed by myself approximately 3 years ago with a Gates kit and has given no issues since, so I was sceptical of (but not completely ruling out) a physical timing issue. I then decided to do a basic test on the wiring using a multimeter with the ignition on. I checked for power across pins 1 and 3 of the connector and checked the signal wire (pin 2) for 5v which all appeared to come back ok. With both of these factors taken into account I decided to proceed and replace the sensor which I bough from my local motor factor. It's an NTK (NGK) branded sensor - part no: CHC3-D025.

After changing the sensor this evening, the fault code has changed to "P034100 - Camshaft Position sensor: Implausible signal" and the long cranking appears to be worse - at least when hot. I will need to wait till the morning to see what it is like with the new sensor when cold. My current thought is that maybe the sensor isn't working properly - it wouldn't be the first time I've used an aftermarket sensor only for it to not cure the issue and then have it cured by using a genuine OE one. Unfortunately the only live data I have available is engine RPM which is reading normally, I can't separate cam and crank speed on the diagnostic tool I have.

I'm also wondering if wiring may actually be a problem - the tests I've done up to now have been very basic. Perhaps checking continuity between the sensor plug and the ECU plug may be a better test?

I'm still sceptical of physical timing being an issue due to the fact that the van runs well. I also feel like that wouldn't explain why the fault code changed after changing the camshaft sensor. I have just ordered the timing tools to check just in case as I borrowed them previously when changing the belt. From what I've read, there is a lobe on the hub of the camshaft sprocket which is what the sensor reads. I will have a look tomorrow and make sure it looks in ok condition but I can't really see how it would have become damaged, however I guess it's worth a look regardless.

It may be completely irrelevant, but I had the battery tested at a Halfords Autocentre yesterday and it tested to be in fine health. I was initially suspecting a battery/starter issue prior to scanning for any fault codes to begin with.

Any ideas or sense checking would be hugely appreciated. I understand and apologise for this possibly being posted in the wrong area. Currently still on limited access.

Cheers!
Matthew
2006 1.9 TDi BLS SWB

[STP]

My only experience of this particular fault was on a previous vehicle and as you described, fitted a pattern part and it didn't fix the issue, can't remember if the message changed but I ended up buying an OEM cam sensor and to my disbelief, it fixed the issue.

Same with the rear parking sensor on a BMW, new Chinese ones did not work, and a real one did (much dearer though)

[matthew_grey2k]

My only experience of this particular fault was on a previous vehicle and as you described, fitted a pattern part and it didn't fix the issue, can't remember if the message changed but I ended up buying an OEM cam sensor and to my disbelief, it fixed the issue.

Same with the rear parking sensor on a BMW, new Chinese ones did not work, and a real one did (much dearer though)

Thanks for the response! Yeah it was an oxygen sensor on 2013 Audi A4 that went bad on me a few years ago, I was a lot less mechanically inclined back then but had my friend scan it and decided to go with changing the sensor myself. EML back on within minutes Took it to a local Audi independent thinking it was a bigger issue and they changed the sensor out for a genuine one from TPS. Problem solved.

I will get a price from VW today and that’ll determine whether I just chance it or not before waiting for timing tools to arrive.

[matthew_grey2k]

Not much change out of £160 from VW for a genuine sensor… ouch. Will hang fire just now and verify timing once timing locks arrive. Might also have a closer look at the wiring as well.

Assuming all good, there seems to be a lot of reputable branded sensors online at good prices. Does anyone have preferences for OEM quality aftermarket sensors? Thinking along the lines of Bosch, Delphi, Valeo, Hella etc.

Will keep this post updated for anyone interested!

Cheers,
Matthew

[STP]

What about a cheap genuine used one from ebay / breaker to test before going too far? Not really a common failure from what I can see so far so it should be better than yours if it is actually bad.

[matthew_grey2k]

Cheers for the response, that’s a good shout. I will have a wee look online and see what’s available. I checked the timing last night and it was absolutely fine so it’s not a mechanical timing issue at least!

Will update with progress for the benefit of anyone else in the future with this issue.

[Popsicle]

I had the long hot start crank issue a couple of years ago, not wishing to sound all doom and gloom but it was a bugger to resolve.

Regarding the camshaft position sensor, does the rev counter show any revs when doing the long crank? If it does then the sensor is probably fine.

Caddy 1.9 tdi engines need to see 280? rpm, IIRC, when cranking for fuel to be injected. If your starter is not in its first flush of youth or your battery is weak, they will cause the long crank when hot. A patch is available to lower the required revs on hot starts, any decent mapper should be able to flash it on to your ecu.

[matthew_grey2k]

I had the long hot start crank issue a couple of years ago, not wishing to sound all doom and gloom but it was a bugger to resolve.

Regarding the camshaft position sensor, does the rev counter show any revs when doing the long crank? If it does then the sensor is probably fine.

Caddy 1.9 tdi engines need to see 280? rpm, IIRC, when cranking for fuel to be injected. If your starter is not in its first flush of youth or your battery is weak, they will cause the long crank when hot. A patch is available to lower the required revs on hot starts, any decent mapper should be able to flash it on to your ecu.

Cheers for the reply! Either the starter or the battery was my initial thought before reading any codes etc as there has never been an EML to suggest any faults stored. Battery is definitely not the culprit as I say it’s been tested and all good there. The starter could still be the issue however as I believe it could be original. With the van having nearly 270k on the clock it’s bound to be feeling its age! Yes it’s registering RPM when cranking, however I was of the impression the tachometer was supplied by the crank sensor - I may be wrong though. I’d read previous about being able to have the map altered to allow better hot starting at lower RPM and while it sounds a good idea, I’d be quite keen to change the starter as opposed to mapping to suit a tired one if that makes sense.

I’ve changed the cam sensor back to the original one now and the fault has reverted back to the original “no signal” fault rather than the “implausible signal” with the aftermarket one fitted. I also forgot to add that when fitted with the new aftermarket sensor the long starting issue was happening cold as well as hot, every time without fail. With the old original sensor fitted its back to just struggling to start when hot.

I think possibly a second hand original sensor may be a cheap way to go next, will keep updated.

[Popsicle]

With it being difficult to start cold, it does seem likely the replacement sensor is faulty. I think it would deffo be worth trying a genuine new or known good used sensor.

When I was chasing my hot start issue I went through all the things suggested on the internet and didn't get anywhere. I had the ecu flashed for the lower start rpm, new starter, new tandem pump and new intank pump and relay, no faults were ever showing. It turned out to be caused by worn injector lobes on the camshaft, this was at around 217k miles. New camshaft and all good again, vans now on over 400k miles, just everything else falling to bits now!

[matthew_grey2k]

In the interests of helping anyone further down the line experiencing similar issues because I hate unresolved forums A genuine sensor fixed the problem. Managed to get a hold of a second hand one for cheap cheap and no more long hot start or fault codes. That’s been a good few hundred miles now.

Cheers everyone for the input and I hope this helps someone in the future!

Matthew

[STP]

Good news. That was my first thought. I had a similar experience and a genuine sensor fixed the issue.