CAN-Bus Comfort System, Checking
CAN-Bus Comfort System, Checking
NOTE:
- If the connector of one of the control units linked to the CAN-Bus comfort system has been disconnected and the ignition is switched on, a fault entry may be made in the other control units linked to the CAN-Bus comfort system. This also applies if the power supply is interrupted, for example by removing a fuse.
- The Instrument Cluster Control Module J285 forms the interface between the two CAN-Bus systems. It is also the dominant control unit in the CAN-Bus comfort system. The control units connected to the CAN-Bus comfort system in the vehicle (equipment-specific) are entered in this control unit via the adaptation function "Guided Fault-Finding" Vehicle Diagnosis, Testing Info. System VAS5051B or Vehicle Diagnosis Service Syst. VAS5052.
- The wiring diagrams can be used to establish the number of control units linked to the CAN-Bus comfort system.
Isolating possible malfunction causes
NOTE:
- The following malfunction locations and types apply to the CAN-Bus comfort system:
- "Group CAN-Bus comfort system"
- - Fault: Data cannot be transferred via the CAN-Bus system
- - In one-wire mode: Data cannot be transmitted on one of the two CAN-Bus wires ( "CAN-Hi " or "CAN-Lo")
- - Missing messages (time out for several control modules): No data received within the specified time period from one or more control units (Instrument Cluster Control Module J285, Vehicle Electrical System Control Module J519, Steering Column Electronic Systems Control Module J527 or Comfort System Central Control Module J393)
- - No communication: No data received from Instrument Cluster Control Module J285, Comfort System Central Control Module J393, Vehicle Electrical System Control Module J519 and/or Steering Column Electronic Systems Control Module J527
- - Check DTC memory: Instrument Cluster Control Module J285, Comfort System Central Control Module J393, Vehicle Electrical System Control Module J519 or Steering Column Electronic Systems Control Module J527 cannot transmit information because of a malfunction in an upstream component.
- - No communication: No data received from Convertible Top Control Module J256 (prior to further fault-finding, check coding of Instrument Cluster Control Module J285 and operating and display module, Climatronic Control Module J255)
- - Check DTC memory: Convertible Top Control Module J256 cannot transmit information because of a malfunction in an upstream component
- "Drive CAN-Bus"
- - Check DTC memory: Instrument Cluster Control Module J285 cannot output information because of a malfunction in a control unit which transmits data on the drive CAN-Bus system (Check DTC memory of Instrument Cluster Control Module J285) "Guided fault-finding" function of Diagnostic Operation System and "Guided Fault-Finding" Vehicle Diagnosis, Testing Info. System VAS5051B or Vehicle Diagnosis Service Syst. VAS5052
Determining malfunction in CAN-bus comfort system
- With the ignition switched off, connect Diagnostic Operation System VAS 5051A e.g. using Diagnostic Cable - 3 Meter VAS 5051/5A and K-Lead Adapter Vas6017B VAS 6017B (or, on vehicles up to VIN 399999 in Model Year 2005 for Saloon and Avant; gradual introduction for the Cabrio in week 46/04 without prior specification of any particular VIN, K-Lead Adapter VAS 6017A) to the 16-pin diagnostic socket in the vehicle. Diagnostic Operation System VAS 5051A, Connecting and Selecting Functions
- Switch ignition on.
- Select function "00 - checking DTC memory - Entire system".
Indicated on display of Diagnostic Operation System VAS 5051A :
All address words stored in the Diagnostic Operation System VAS 5051A are now consecutively transmitted to the vehicle via the signal wire.
Indicated on display of Diagnostic Operation System VAS 5051A:
- Display field -1 - indicates the address word currently being transmitted by the Diagnostic Operation System VAS 5051A.
- Display field - 2 - shows which control units have responded. The number and type of DTC memory in this control unit are also displayed.
- Wait until display zone -1 - indicates "Function completed".
NOTE:
- If a different or an additional fault has been stored in a control unit with which the other control units cannot exchange data, rectify this fault before checking the CAN-Bus wire system.
- In the event of a malfunction in a control unit, there may be problems with the exchange of data with the other control units although this fault does not directly affect the CAN-Bus system.
- Check the part number and the corresponding index of the control unit with which there is no communication.
Malfunction(s) on the CAN-bus comfort system are only indicated by the operating and display module, Climatronic Control Module J255
- Check coding of operating and display module, Climatronic Control Module J255 and Instrument Cluster Control Module J285 "Guided fault-finding" function of Diagnostic Operation System VAS 5051 and "Guided Fault-Finding" Vehicle Diagnosis, Testing Info. System VAS5051B or Vehicle Diagnosis Service Syst. VAS5052.
- Check signal wires to operating and display module, Climatronic Control Module J255 for open circuit or wiring resistance. Wiring resistance: max. 1.5 ohms
NOTE:
- Pay particular attention to the possibility of loose contacts in the wires and connectors.
If this malfunction is not displayed for all connected control modules, the problem may be an open circuit at a connection in the wiring.
Malfunctions on the CAN-bus comfort system are indicated in another control module
- Check the signal wires and the corresponding screening between the various control modules linked to the CAN-Bus comfort system for open circuit and wiring resistance. Wiring resistance: max. 1.5 ohms
- Check the signal wires and the corresponding screening between the various control modules linked to the CAN-Bus comfort system for mutual short circuit or short to Ground (GND)/positive. "Guided Fault-Finding" Vehicle Diagnosis, Testing Info. System VAS5051B or Vehicle Diagnosis Service Syst. VAS5052
NOTE:
- Pay particular attention to the possibility of loose contacts in the wires and connectors.
- If this malfunction is not displayed for all connected control modules, the problem may be an open circuit at a connection in the wiring.
If no malfunction can be found and this malfunction is displayed for all control units linked to the CAN-Bus comfort system, the problem is in one of the connected control modules.
- Check version, coding and adaptation entered for the Instrument Cluster Control Module J285. "Guided Fault-Finding" Vehicle Diagnosis, Testing Info. System VAS5051B or Vehicle Diagnosis Service Syst. VAS5052
- Check version and coding of other control units linked to the CAN-Bus comfort system (e.g. Vehicle Electrical System Control Module J519 , Steering Column Electronic Systems Control Module J527 ). "Guided Fault-Finding" Vehicle Diagnosis, Testing Info. System VAS5051B or Vehicle Diagnosis Service Syst. VAS5052
- Disconnect all control units except the Instrument Cluster Control Module J285 (interface with drive CAN-Bus system) and the Steering Column Electronic Systems Control Module J527 from the CAN-Bus comfort system
- Erase DTC memory of Instrument Cluster Control Module J285 "Guided fault-finding" function of Diagnostic Operation System VAS 5051 and "Guided Fault-Finding" Vehicle Diagnosis, Testing Info. System VAS5051B or Vehicle Diagnosis Service Syst. VAS5052
- Check DTC memory of Instrument Cluster Control Module J285 and Steering Column Electronic Systems Control Module J527 "Guided Fault-Finding" Vehicle Diagnosis, Testing Info. System VAS5051B or Vehicle Diagnosis Service Syst. VAS5052.
If the malfunction in the CAN-Bus comfort system is now no longer displayed, the problem is in one of the disconnected control modules.
- Consecutively reconnect the various control modules.
- Check the DTC memory after connecting each control unit.
- Replace the control unit following installation of which the malfunction is displayed again.
If the malfunction in the CAN-Bus comfort system is still displayed, there is a problem with the Instrument Cluster Control Module J285 or the Steering Column Electronic Systems Control Module J527.
- Disconnect the Steering Column Electronic Systems Control Module J527 and connect a different control module (e.g. operating and display module, Climatronic Control Module J255).
- Check DTC memory of Instrument Cluster Control Module J285 again.
NOTE: The defective control module can be established by disconnecting the Steering Column Electronic Systems Control Module J527 and connecting a different control module.
- Replace the defective control unit.