CMP/CKP Sensor fault
 

Found and interesting problem with my WG and I would like to share the solution:

after finishing the warm-up cycle the engine shutdown during low load situations ( e.g.traffic stop, coasting).
Jeep Diag showed a CMP CPK fault P0340.

Okay, replaced the crank and cam sensor.
Problem still occured with the same P0340 fault.
Needless to say that I checked the wiring and the delivered signal itself. As expected the signal was shown on the oscilloscope cearly for both sensors.
So it is not the Cam or Crank speed sensor.
also checked the fingers on the flywheel for straightness, bent metall pieces are kown for giving problems. This can be visually checked after removal of the plastic cover between engine and transmission.

After reading through the manual, it turned out that the IAT sensor (intake air temperature) is also related to P0340.
After exchange of the IAT everything is back to normal.

So in this case it was a faulty IAT sensor.

Don't buy cheap CMP sensors...

Fault description:
During engine warm up, when reaching close to operating temperatures the engine hesitated and simply shut down. Could be restarteded without a problem.

jeep Diag diagnostics: P0340 CMP circuit fault

Turned out not being a wiring problem as assumed. It was a faulty sensor. Again!

Brand: VEMO - 8€

Exchanged against a Magneti Marelli, 28€, thats works perfectly.

So the differences in fault apperances and symptoms are very minor. After warm up and low load situation (IAT), and now it was during warm-up (CMP).

Since it is so important I ordered a second one along with a crank position sensor, an Air intake sensor and boost pressure sensor.

I do have a little peli case to carry them as spares since you probably can't get those while on the move.

If you have a wiring problem with the CMP- the engine will simply not start. Once it's running you only get an Out-of-sync message.

Remember- if you want to test the wiring test the 5V power supply at the sensor, test the return line against battery minus. The sensor wiring must be measured at the ECM - you need to read between 0.2V and 4,5V if it's higher or lower then the sensor is fried.

Picture shows Sensor connector view, not wiring.