help with trouble codes in BCM EPS CEM
 

Hi everyone,

I took my 2008 v50 1.8 to the dealership for a software update in an effort to remedy an idle issue I have when the engine is warm.

The software update didn't help but they gave me a printout of some trouble codes. Can anyone help me identify what they might point to?

I have the following active codes:

CEM-DE01: Communication with BCM control module Signal missing

CEM-DF11: CAN-H, high speed network signal missing

DIM-0001: Mileage Manipulated

EPS-0081: Vehicle speed faulty signal

Am I right in thinking that the EPS module receives vehicle speed information from the BCM module? Does this signal go via the CEM? Is the missing CAN signal this missing signal?

There are no codes referring to the individual wheel speed sensors so is it safe to assume that I can rule out these?

Any and all help greatly appreciated.

And just FYI... The idle issue is as follows... When engine is warm and presumably running in closed loop the engine rpm will drop when clutch pedal is depressed approaching junctions and the like. I've replaced the pcv valve and hose, intake manifold gaskets, new throttle body, new egr valve, new swirl flap actuator solenoid, new plugs, new clutch pedal switch, new upstream O2 sensor, new MAP sensor, new air filter.

Next on the list is crankshaft position sensor.

My hunch now is that vehicle speed isn't being reported correctly so overrun fuel cut is not being disengaged in good time

Ours does that very occasionally. I'll be interested to hear what solves it for you although granted my post here doesn't help you much.

Might be worth checking the connections to the CEM (below the glove compartment). The missing CAN-H signal could well be the root cause for all your problems. Check that there isn't any corrosion in the plugs and that they are firmly seated in the holders. Disconnect the battery before messing with the CEM.

Thanks Teddy1975, I did a rudimentary cleaning of the connections a couple of months back but I think I'll take it out of the car completely and give it a proper go.

iainmd, this is the one of a couple of issues that I've been unable to resolve with this car but I'll post an update if I get it sorted.

Just an update.

I had the CEM apart earlier. It was badly corroded as a result of what looks like electrolytic corrosion between pins up against the circuit board. This was only apparent after removing the CEM from its plastic casing.

The pictures show before and after.

I've cleaned all the pins and will pop it in the car tomorrow and see how it goes.

Looks like a new CEM might be needed.

https://ibb.co/1Lj0syt

https://ibb.co/yhqsWM8

Ouch, that doesn't look too good. It might be salvageable even if the test today failed, but would require firm knowledge of soldering and a bit of luck.

Yeah, it's not great... The CEM went back in today. Not before I isolated the base of the affected pins with some heat shrink to minimise stray currents and then coated the base with lithium grease as shown in the pictures to protect the area from oxidation.

No change to my idle symptoms and I don't have the facility to check the trouble codes myself. That will have to wait for the time being.

Car feels much the same to be honest. Perhaps my clean up the circuit board had no positive affect and the solution is a donor cem.

Bit of a dead end at the moment.

https://ibb.co/vPH9Gc3

https://ibb.co/WzGH8QS