Description

Communication on the CAN bus fails due to CAN ´bus off´ conditions.

'bus off' : If the error counter of a CAN controller exceeds the value 255, the CAN controller will assume the 'bus off' status. The CAN controller is disconnected from the CAN bus using an internal logic function and does no longer participate in the bus activities.

CAN messages can no longer be received nor sent.

Effects on the driving operation

No CAN communication via CAN controller 1 of the transmission control unit possible.

Vehicle does not drive or only with restrictions.

Possible causes

Short-circuit between CAN1-H and CAN1-L or short-circuit of a CAN1 line to ground.

* A bus node is sending with incorrect bit rate.

* Another defective control unit is connected to the CAN1 bus.

* Defective CAN1 transceiver in the E300 control unit.

Connector pin assignment of transmission control unit

Pin	Stecker A	Stecker B	Stecker C	Stecker D
1	SHIELD	EK	FLEXI-1	-BATT
2	TIM+	DK	---	IGN
3	TIM-	SK	FLEXI-3	FLEXI-11
4	N1+	RBK	FLEXI-4	K-LINE
5	N1-	TB	FLEXI-5	CAN1-H
6	N2+	---	FLEXI-6	CAN1-H
7	N2-	RBG	FLEXI-7	CAN-SHLD
8	N3+	PB	FLEXI-8	CAN1-L
9	N3-	WR	FLEXI-9	CAN1-L
10	---	WP	FLEXI-10	CAN2-H
11	---	---	FLEXO-2H	CAN2-H
12	EKM	FLEXI-12	FLEXO-4H	CAN2-L
13	DKM	S-GND	FLEXO-3H	CAN2-L
14	SKM	OIL-LVL	FLEXO-5L	CAN1-R
15	PBM	T-SUMP	---	---
16	TBM	---	---	FLEXO-1L
17	RBKM	T-CONV	---	CAN2-R
18	MVM-GND	MV-GND	---	+BATT

Place of action

CAN bus

Troubleshooting

Instruction

Measure resistance between CAN1-H and CAN1-L ( ~ 60 Ohm ).

Check cabling.

* Measure resistance between CAN-H1 and CAN1-L to ground: The resistance must lie well above 1 kohm.

* Check whether the correct dataset and correct CAN1 protocol are active.

* Disconnect all control units from the CAN1 bus one after the other and check whether this eliminates the fault.

* Replace E300 control unit.

Setting conditions of the event

No description available.

Test conditions of the event

No description available.

Final function check

If the defective component cannot be clearly identified, you should try to reproduce the fault:

• Reinstall the component in the vehicle.
• Test the function.

After the fault has been eliminated, the following steps have to be carried out:

• Conduct a test drive with function check.
• Read out the fault memory.
• Check the transmission for leaks.
• Perform a final visual inspection.

These steps are necessary to ensure the entire vehicle functions.

See also:

		Aftersales service index