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View Full Version : P0343 - Camshaft Position Sensor (G40): Signal too High



turbo_bootin
05-16-2012, 04:33 PM
16727/P0343/000835 - Camshaft Position Sensor (G40): Signal too High

I have this code. It usually takes 2-3 tries before the engine turns over.

2001 1.8TQM AWM

Possible Causes

Wiring from/to Camshaft Position Sensor (G40) faulty
Camshaft Position Sensor (G40) faulty
Timing misaligned


I have:

Replaced Cam Position Sensor (6mo ago)
Checked continuity from CPS to ECU
Verified timing



Today I replaced my failed hydraulic TB tensioner with the IE manual one. I had hoped that this was the cause the DTC, but it wasn't. I double checked the timing with the factory marks.

Last week, I pulled off the CPS and saw that one of the prongs in the connector was pushed in a little bit. So, I pulled it out to the correct length and glued it in place. This did not correct the DTC. I'm wondering if this CPS is just a piece of junk (MTC brand from ECS) and I should replace it with Bosch or the like.

Any ideas?

ImTheDevil
05-16-2012, 05:21 PM
Have you tried actively clearing the code? Or are you just doing work and waiting for the light to go out? A cam phasing fault code could have an effect on emissions so it may require you to actively reset the light.

turbo_bootin
05-16-2012, 05:24 PM
Yes. It instantly comes back when the car is running.

bmarshall
05-16-2012, 08:12 PM
Have you checked power, ground and the signal wires with a multimeter? Not a continuity check.

Turbo Nerd
05-16-2012, 08:21 PM
You might have a possible faulty can chain tensioner... That will also cause that DTC to show up.

Alphonse
05-16-2012, 09:02 PM
you can directly clear the fault code!!!!!

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turbo_bootin
05-17-2012, 08:17 AM
Have you checked power, ground and the signal wires with a multimeter? Not a continuity check.

Yup.


You might have a possible faulty can chain tensioner... That will also cause that DTC to show up.

Wouldn't I hear the rattling from it?

walky_talky20
05-17-2012, 11:33 AM
A bad CCT won't cause the car to randomly not start, though. Failure of the Cam sensor (or just unplugging it) will cause the engine to only start with about a 40% success rate. Usually have to try 2 or more times to get it to fire. Sometimes there can be a backfire involved because the ignition and fuel injection are 180 degrees out of sync with the valve-train. Simply put, without a good signal from the Cam Sensor, the ECU takes a "guess" as to which stroke is the compression stroke. It knows where TDC is from the crank sensor, but without the cam sensor it has a 50/50 chance of guessing the stroke correctly. The kicker is that it always guesses the same thing, it just depends on where the engine comes to rest as to whether that "guess" is correct or not. On a 1.8T, most of the time it seems to come to rest in the wrong spot. So you have to try a few times before the magic happens.

So the problem is almost definitely the lack of a good signal from the cam sensor. The best thing to do would be to swap the sensor with a car that is working fine. Then you instantly know where the trouble is. The scientific way would be to put a scope on the cam sensor signal wire and see what the waveform looks like compared to a known good signal. That would confirm the diagnosis without actually touching any parts.

Most likely this is all caused by you cheaping out and buying a chinese cam sensor. Because it is electrical, ECS probably won't help you. Personally, I'd rather find a used Genuine Audi part than get another chinese piece. But it's up to you.

turbo_bootin
05-17-2012, 02:33 PM
A bad CCT won't cause the car to randomly not start, though. Failure of the Cam sensor (or just unplugging it) will cause the engine to only start with about a 40% success rate. Usually have to try 2 or more times to get it to fire. Sometimes there can be a backfire involved because the ignition and fuel injection are 180 degrees out of sync with the valve-train. Simply put, without a good signal from the Cam Sensor, the ECU takes a "guess" as to which stroke is the compression stroke. It knows where TDC is from the crank sensor, but without the cam sensor it has a 50/50 chance of guessing the stroke correctly. The kicker is that it always guesses the same thing, it just depends on where the engine comes to rest as to whether that "guess" is correct or not. On a 1.8T, most of the time it seems to come to rest in the wrong spot. So you have to try a few times before the magic happens.

So the problem is almost definitely the lack of a good signal from the cam sensor. The best thing to do would be to swap the sensor with a car that is working fine. Then you instantly know where the trouble is. The scientific way would be to put a scope on the cam sensor signal wire and see what the waveform looks like compared to a known good signal. That would confirm the diagnosis without actually touching any parts.

Most likely this is all caused by you cheaping out and buying a chinese cam sensor. Because it is electrical, ECS probably won't help you. Personally, I'd rather find a used Genuine Audi part than get another chinese piece. But it's up to you.

Thanks Walky. I did some logging in VCDS and my ignition is firing at about 20 deg BTDC at idle, instead of 0~12 deg BTDC, which seems to point to a faulty sensor.