Grasscutter
New Member
Grateful to anyone who can help me with a CEL problem.
The car is a 2004 C180K with M271 engine. For some time the CEL light had been on with a circuit fault for the exhaust camshaft position sensor. Checking the output of the sensor with a 'scope confirmed it was faulty. However, replacing it didn't fix the problem until I finally 'scoped the new sensor to find the output was permanently high. Another new cam sensor has finally sorted that one, but in the meantime I find I've been getting a new error, P0020 "A" Camshaft Position Actuator Circuit.
I've checked the continuity of the wiring of the cam magnets back to the ECU. Unable to fully check the return as these go to "Circuit 87M2e connector sleeve" and I haven't a clue where that is. I was able to verify the returns (pin 2) of both cam magnets are connected together as the circuit diagram shows, so either they're both okay or neither connect back to 'circuit 87M2e connector sleeve'.
I noticed something else while trying to fault find this one. Having had the drivers door open with the engine running, the interior light was changing in intensity, but not as I expected. Bright at idle, dimming slightly as I increased the revs and bright again with the revs at steady state. This led me to measure the battery voltage: 13.7V at idle, 14.2V above idle, dipping to about 13.2V when blipping the throttle. I believe the regulator of the alternator is under engine ECU control. Is it programmed to back off the charge rate if rapid acceleration is called for?
Just for experiment I drove the car briefly with the alternator control wire disconnected. I got P0020 as a pending fault just once rather than bringing on the CEL quickly as it would have done before. Am I looking at a possible alternator fault or is the engine management advanced enough that it won't add another battery drain like the cam magnets if the alternator isn't charging? Alternator has decent brushes and maintains 14.2V at any revs I hold the engine at above idle. Its only moving up from idle or a rapid blip of the throttle that will cause the voltage to momentarily come down.
I have changed out both cam magnets, but the problem's still there. Now am completely stuck. Can anyone help?
Kind regards,
Mike
The car is a 2004 C180K with M271 engine. For some time the CEL light had been on with a circuit fault for the exhaust camshaft position sensor. Checking the output of the sensor with a 'scope confirmed it was faulty. However, replacing it didn't fix the problem until I finally 'scoped the new sensor to find the output was permanently high. Another new cam sensor has finally sorted that one, but in the meantime I find I've been getting a new error, P0020 "A" Camshaft Position Actuator Circuit.
I've checked the continuity of the wiring of the cam magnets back to the ECU. Unable to fully check the return as these go to "Circuit 87M2e connector sleeve" and I haven't a clue where that is. I was able to verify the returns (pin 2) of both cam magnets are connected together as the circuit diagram shows, so either they're both okay or neither connect back to 'circuit 87M2e connector sleeve'.
I noticed something else while trying to fault find this one. Having had the drivers door open with the engine running, the interior light was changing in intensity, but not as I expected. Bright at idle, dimming slightly as I increased the revs and bright again with the revs at steady state. This led me to measure the battery voltage: 13.7V at idle, 14.2V above idle, dipping to about 13.2V when blipping the throttle. I believe the regulator of the alternator is under engine ECU control. Is it programmed to back off the charge rate if rapid acceleration is called for?
Just for experiment I drove the car briefly with the alternator control wire disconnected. I got P0020 as a pending fault just once rather than bringing on the CEL quickly as it would have done before. Am I looking at a possible alternator fault or is the engine management advanced enough that it won't add another battery drain like the cam magnets if the alternator isn't charging? Alternator has decent brushes and maintains 14.2V at any revs I hold the engine at above idle. Its only moving up from idle or a rapid blip of the throttle that will cause the voltage to momentarily come down.
I have changed out both cam magnets, but the problem's still there. Now am completely stuck. Can anyone help?
Kind regards,
Mike