Test Preparation for DTC Readout Note: A stored DTC is erased, if the connector of the 4MATIC control module (N30/3) is unplugged or if the battery is disconnected. 1. Connect impulse counter scan tool to data link connector (X11/4) as shown in Figure 1. Note: Connect yellow wire from impulse counter scan tool as follows: 4MATIC control module (N30/3) socket 5 2. Engine: At idle. 3. Read DTC memory of 4MATIC control module (N30/3). See section 0. Note: After successful repair erase DTC memory with engine running. The following faults are not stored by the 4MATIC control module: 4MATIC function indicator lamp (A1e25) defective. 4MATIC MIL (A1e24) defective. Oil pressure switch (A7/2s1) defective.

Diagnostic trouble code (DTC)	Possible cause	Test step/Remedy 1)
	No faults recognized. In case of complaint:	23 (entire test)
	4MATIC control module (N30/3)	N30/3
	Stop lamp switch (4-pole) (S9/1)	23 8.0, 9.0
	Left front axle VSS sensor (L6/1)	23 13.0
	Right front axle VSS sensor (L6/2)	23 14.0
	Rear axle VSS sensor (L6)	23 15.0
	Axle VSS sensors (L6, L6/1, L6/2) or ABS control module (N30)	Check wiring for open circuit, Check N30.
	Overvoltage protection relay module (87E/87L/30a, 9-pole) (K1/2) or front axle drivetrain valve (A7/2y1) or central differential lock valve (A7/2y2)	23 1.0, 2.0, 16.0, 17.0, 19.0, 20.0
	Overvoltage protection relay module (87E/87L/30a, 9-pole)(K1/2), central differential lock valve (A7/2y2) or rear axle differential lock valve (A7/2y3) or stop lamp switch (4-pole) (S9/1)	23 1.0, 2.0 ,8.0, 9.0, 16.0, 17.0, 18.0, 19.0, 20.0
	Overvoltage protection relay module (87E/87L/30a, 9-pole)(K1/2) or rear axle differential lock valve (A7/2y3) or stop lamp switch (4-pole) (S9/1)	23 1.0, 2.0,8.0, 9.0, 18.0, 20.0
	Overvoltage protection relay module (87E/87L/30a, 9-pole)(K1/2) or steering angle sensor (N49)	23 1.0, 2.0, 10.0, 11.0, 12.0

1) Observe Preparation for Test, see 22.