HI all

Recently did loads of work on my R53 (oil pan gasket, supercharger pulley, newman cam install and rocker cover, water meth, injectors etc) I also replaced the cam sensor for a new one as the old was leaking.

The car drove fine for 100 miles or so, then the DSC light came on, and I have a P0340 PENDING code. It also occasionally logs a P0341 code, as a current code. It never sets the check engine light, but puts the DSC light on every time. The DSC module has a stored code along the lines of "Cam sensor signal missing from DME can bus, code present in DSC module as long as this exists"

I fitted a new genuine cam sensor, same thing.

The car has lots of power and drives fine with the light off. The P0340 is random, comes on and off, sometimes its on at idle, sometimes not.

If I warm the car up and erase the code, then pull through the revs in 1st or 2nd, it usually comes on above 4000rpm. Once the DSC light is on it will go in and out of "limp mode".

With the old sensor, once the DSC light was on, it was in limp mode with no power above 3000rpm.
With the new sensor, once the DSC light comes on, the power comes in and out throughout the rev range.

I am starting to think the timing has jumped 1 tooth on the cam, but AFAIK, the only way to check the timing is to remove the timing chain cover and check the position of the coloured links (Really...) It also runs so well at idle, and across the rev range that I am suspicious its jumped.

There is no chain noise, or noise from the top end etc.

I am stumped, and any help would be appreciated.

 

change out your tmap sensor first, those are the symptoms of a bad tmap. Don't ask me why as the codes are completely unrelated to that sensor but I've had 2 cars with the same symptoms+dsc light and it was the tmap both times.

 

I am going to scope the output of the cam and crank sensors tomorrow. I have a feeling its the Crank position sensor feeding bad data to the ECM which then gives a cam implausible.

I will sanity check the output of the tmap sensor at the same time. Thanks

 

I don't test I just swap as the sensors are cheap and easy to get to. My theory is the tmap intermittently shorts out causing the non related codes and dsc error.

 

Update. Not the Tmap, swapped them and the MAP and the same thing happened.

Scoped the output of the sensor, its not regular as it should be:


In comparison to a 10 minute period where it had no codes and was running ok:



And then with the output of the cam sensor disconnected from the ECU:


Its much noiser as the voltage is much lower without the ECU's internal pull up/down resistor, but its consistent.

I fed the CAM sensor a 12v supply independent of the ECU and it did not change, so I am leaning towards a faulty engine ECU

 

unfortunately I've had that happen too, at least they are cheaper now