2007 MC N12. Does anyone know how this should behave (pin 19 yellow wire). I get 0V unlocking car. Then a split second voltage when I push in key then back to zero. And with ignition on I get continuous voltage but the voltage is about 0.5V less than battery voltage! Sometimes car is fine at first but then get lots of things failing - ABS, tyre pressure, restraints system, Speedo, power steering, fuel gauge goes up and down, steering column lock symbol. Wondering if CAS is the problem. Any help please. I’m at the end with this car which is a shame because otherwise car is great.

 

Sounds like FRM module.

 

Hi Minimi2, thanks for your reply. Why do you think FRM please?
I've found something else that may be relevent - Brake light switch signal at ABS connector, pin 32, red/blue has a small voltage even when brake pedal is not pressed (0.12V), I expected 0V?
Brake lights seem to work ok, as does everything else that appears to come through the FRM...
I think FRM needs coding to car so not a simple swap to try?

 

I am trying to solve a load of warning light issues, ABS, airbag, steering lock, speedo not working, fuel gauge behaving wierd, throttle valve actuating randomly (I think), very occasional crank no start.
These are the codes I'm getting, sometimes I get more. I have put a new wired in for wheel speed signal CAS to ABS which I thought was iffy.


All units have good power and ground. I was looking at the 15 wake up out of the CAS (pin 19 yellow wire).
Does anyone know how this should behave. I get 0V unlocking car. Then for a split second I get a voltage spike when I push in key but then back to zero. And with ignition on I get continuous voltage but the voltage is about 0.5V less than battery voltage!
Can anyone help please

 

Were you able to diagnose your gremlin? I've been dealing with similar issues on my car. Had a slow current draw on new battery to the point of no start after sitting for ten days, tried a jump start with 50 amp jump feature on charger and I've toasted CAS and DME communication, I'm down for the count, Hope your problem was a cheaper repair.

 

hi. So finally sorted it. It was a bad abs module. One of the first things I did was send unit off for repair but it came back not faulty so have spent months tinkering with wires, CAS etc. in the end sent ABS off again and told them fault isn’t always there at switch on. The replied they couldn’t fix it. Got a second hand one. Fitted it. Only fault code was unit not coded to car. Eventually sorted that and all ok. Basically the speed signal from abs is used for lots of things hence multiple errors. Steering lock needs to check car is still. PAS is speed sensitive. Airbags need to know how fast your going. Speedo obviously. Fuel level variation I assume this is some kind of smoothing algorithm. Throttle & engine management needs speed signal too. Hope this helps someone.