ahmedalalousi

Dear all,

Here's a bit of history behind this monster; it's been nothing short of very frustrating trivial pursuit exercise, so thought to share lest anyone has any insight ..

1. In Limp Home mode, with ESP failure message displayed on console
2. DAS/Xentry displays all sorts of errors, most notably C01022 fault
3. BAS errors and BAS warning light on
4. Revving not possible, stuck on around 1000 RPM.
5. Engine runs rough, as if misfiring.
6. Steering angle short circuit fault
7. Communication with read DCMs not possible; DAS throwing an error to the effect that communication with DCMs not possible due to CAN bus disconnect. Rear passenger windows unresponsive - cannot be taken up or down.

• Starting with (6) above, took the steering wheel out, rewound and aligned the steering angle sensor, that fault cleared.
• Reading values from steering angle sensor and break switch now possible
• (3) was cleared by tracing the BAS relay into the right engine compartment fusebox. Took it out, put it back in, BAS fault cleared, and not come back. Turned out to be dirty contacts
• Working on (2), it turns out that the Green/Green with White pair that hooks up the ESP to the Engine CAN bus is actually cut and taped, inside left side sill, near foot well. No continuation of the loom where cut was observed. Took the whole interior and dash out, and physically traced it to the ESP. Connecting this pair to a point on the engine CAN bus cleared the CAN communication fault, but now a fault reported stating unable to read right-hand rear RPM sensor. Connections are fine on visual examination while being taken apart.
• Working on (7) above, SAM reports healthy with no errors. Centre console module (can't remember name), reports healthy.
• Turned my attention to the CAN Bus Z-connector sleeves. ESP, ME2-SFI and a whole bunch of other Mercedes junk taps off Z37/13 and Z37/14, which is illustrated as being behind (?) the firewall in the car's interior, hence pulled the whole interior out, seats, carpets and dash included. No cuts there.
• All CAN connections to the back of the car, which are sockets inside sills, have been verified to be connected and intact. Cannot figure out where the CAN bus is cut between front and back of car.
• In the weirdest, worst possible engineering practice I have ever come across, MB decided to run the ENGINE, yes the ENGINE CAN bus all the way to the headlights. And that's nothing to say of how poorly designed and dimensioned the wiring loom is. Yuck !!. Anyway; Live actuations showed that only left unit is able to level up and down, so turned my attention to the right hand side light nodule. Found water-induced oxidisation on the High side of the CAN bus (CAN-H) at that module.

Is anyone the wiser than I am? where else is the CAN bus tapping to get to the rear door modules?

Am I correct in assuming that once CAN communication has been re-established, then I should be able to clear the adaptations and continue with the rest of the debug nightmare to get the car out of limp home?

I shall be posting photos of all of this in attachments to this post soon as I had them.

Plutoe

Your thinking is old school. You need to go back and reread the CAN bus for the W210 E55. Each door control module is connected to the CAN bus(look at the connector) like every other module is connected to it's respective bus(engine,chassis, bla bla).

When you get a message that "unable to communicate with bla bla module" that does not typically mean there is a bus issue, it usually means the module is faulty and not able to communicate----so while you have been running around trying to find a broken bus---it ain't broken the module is broken.

Yes once all the connections are made---you interrogate the system and it will list all the faults-----correct the faults and you will correct the limp mode!!

ahmedalalousi

OK Mr. new school. So, let's put you right, because I got this pile of bother running and revving now, and the report is in the original thread.

And just before you make a total idiot out of yourself, stop for a couple of minutes to actually think of who might be at the other end of the message.

ahmedalalousi

Eureka !! figured this beast out, and here's the report:

Summary of Faults Found

1. Severed engine CAN bus wires between ESP (N10/1) and the rest of the bus. This was cut and left taped, probably by the genius trying to fix it before I got it. Reconnecting this to the Z37/2 and Z37/3 sleeves on the left hand side front foot well restored communication. Scope traces confirmed correct waveforms, and sniffed CAN messages in order. C01022 type errors stopped appearing once cleared.
2. Faulty contacts at the EZS meant that CAN wakeup packets were not consistently generated and delivered. Once cleaned, CAN errors relating to ESP and ME-SFI cleared. This did not clear DCM communication errors - see below.
3. Re-alignment of Steering Angle Sensor, underlying mechanical linkage and activation of the steering angle sensor cleared that fault from the ESP
4. Integrity check of the interior CAN bus revealed corroded X35 connector in the right sill, thanks to great MB engineering. Cut and re-terminated to restore communication with rear of interior. Still no comms with rear DCMs.
5. Scope readings from the rear DCMs are conclusive that messages are being relayed correctly; my next port of call is taking the DCMs apart at the component level; one for another day.
6. B35 at the throttle body corroded; you guessed it, first class German Engineering again !!. Took socket apart, repaired and re-terminated, restoring power. No actuations at the throttle body, so took it apart to find crushed plastic gear. Replaced, restoring free movement to the throttle body.
7. Bootstrapped EM-SFI, reset adaptations and voila: running on all 8, like an AMG engine should, just waiting to be unleashed

Next stop, the rear DCMs. I find it odd that both are unresponsive, so let's see what the rest of the debug exercise will reveal. Will keep this thread posted.