Description

Communication on the CAN bus is disturbed due to ´CAN warning´ conditions.

A ´CAN warning´ is caused by a CAN controller receiving too many invalid data. A CAN controller in warning condition can still read data from the CAN bus but it can no longer send data. The warning condition is automatically cancelled once the CAN controller has received a certain percentage of valid data.

Effects on the driving operation

Transmission shifts sporadically to neutral.

Lighting of the gear range selector becomes dark.

Possible causes

CAN bus incorrectly terminated (bus terminating resistor).

There is a cable break, loose contact or too high contact resistance in the CAN cabling.

Connection of the CAN gear selector switch

The jumpers on the transmission control unit (D13 to D17) and on the CAN gear range selector (6 to 7) activate the integrated CAN terminating resistors since the transmission control unit and the CAN gear range selector are usually the only CAN bus nodes at CAN2. The CAN bus must always be wired with the terminating resistors on both sides.

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

Connector pin assignment of CAN gear selector switch

Pin	Name	Pin	Name	Pin	Name
1	IGN	6	CAN-H	11	FLEXI-4
2	-BATT	7	CAN-R	12	FLEXI-5
3	CAN-L	8	FLEXI-1	13	FLEXI-6
4	CAN-L	9	FLEXI-2	14	FLEXO-1H
5	CAN-H	10	FLEXI-3

Place of action

No description available.

Instruction

Check the cabling (cable break, loose contact, high contact resistance).

Measure between CAN-H and CAN-L: the resistance must be approx. 60 ohms - install / repair bus terminating resistor if necessary.

Setting conditions of the event

No description available.

Test conditions of the event

No description available.

Troubleshooting

1. Measure resistance between CAN-H and CAN-L. The nominal value is 60 Ω.
   A terminating resistor of 120 Ω each is installed at each end of the CAN bus.The two terminating resistors together yield a parallel connection resistance of 60 Ω.
2. Check CAN wiring including plug-in connectors for loose contact and contact resistances.

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