R230, SL500 apparent fault with rear SAM module

[mckcol]

Hi All, problems with my R230 SL500 that I have owned for 3 or 4 years.

Roof was down, car left for an hour. On driving off, came up on dashboard with red battery on left display and visit workshop on right.
Roof refused to go up, various functions not working, fuel guage reading zero, rear indicators not working (front ok), windows not doing their auto retract when opening door.
I disconnected both batteries for 5 mins, no change.
Drove for 30 mins and stopped at services. After 15 min stop, all had reset and was fine. So put roof up to continue our trip.
Fault has now returned.
Obviously can't be a fuse.
Battery voltages seem ok, have repeated diagnostics with a charger connected (13.5V on battery)
Checked on diagnostics, all seem to be related to the rear SAM module. I have checked all fuses, and connections to this module.
Faults:
B1076 Control unit N10/8 (Rear SAM control module) is not transmitting data on the CAN bus.
B1021 Control unit A37 (PSE control module) is not transmitting data on the CAN bus
B1091 Control unit N52 (RVC Control module) is not transmitting data on the CAN bus
Faults are current and can't be cleared.
I am thinking (hoping!) that it could be simply a wire break on the CAN bus to the rear SAM module.

Can anyone point me in the direction of where this CAN bus runs, where the ends are, so I can try some continuity checks?
Sadly car currently unuseable
Thanks all!

 

[oldguy57]

You may have already done so, but have you checked the output from the alternator to both batteries. Red battery light is sometimes associated with failing alternator/regulator. Throws all sorts of weird codes.

 

[pioneercollector]

I second the comment from 'oldguy57' I had a similar issue with my own SL500 R230 recently and it was the alternator - all changed and the car is perfect now.

 

[colinallcars]

Hi All, problems with my R230 SL500 that I have owned for 3 or 4 years.

Roof was down, car left for an hour. On driving off, came up on dashboard with red battery on left display and visit workshop on right.
Roof refused to go up, various functions not working, fuel guage reading zero, rear indicators not working (front ok), windows not doing their auto retract when opening door.
I disconnected both batteries for 5 mins, no change.
Drove for 30 mins and stopped at services. After 15 min stop, all had reset and was fine. So put roof up to continue our trip.
Fault has now returned.
Obviously can't be a fuse.
Battery voltages seem ok, have repeated diagnostics with a charger connected (13.5V on battery)
Checked on diagnostics, all seem to be related to the rear SAM module. I have checked all fuses, and connections to this module.
Faults:
B1076 Control unit N10/8 (Rear SAM control module) is not transmitting data on the CAN bus.
B1021 Control unit A37 (PSE control module) is not transmitting data on the CAN bus
B1091 Control unit N52 (RVC Control module) is not transmitting data on the CAN bus
Faults are current and can't be cleared.
I am thinking (hoping!) that it could be simply a wire break on the CAN bus to the rear SAM module.

Can anyone point me in the direction of where this CAN bus runs, where the ends are, so I can try some continuity checks?
Sadly car currently unuseable
Thanks all!

You say the battery voltages seem OK, what are the readings without the charger connected and the engine off after standing overnight?