Fault code 1893: Diagnosis/troubleshooting

WARNING: Danger of injury from limbs being trapped or severed.

NOTE: To gain access to the driver's memory seat adjustment control unit, tilt the driver's seat back.

NOTE: Visual inspection: In the next troubleshooting section, first check that the affected pins on the driver's memory seat adjustment control unit plug connection are not damaged or corroded. The wiring and plugs of the affected components must also be checked for external damage and correct contact. Repair damaged or corroded pins if possible, otherwise replace affected pins. Repair or replace damaged wires.

NOTE: Sporadic faults: In the event of sporadic faults, wiring points attached to moving parts on and in the vehicle must be checked systematically. Various statuses that can cause faults must be simulated with the help of the wiring diagram.

NOTE: Battery voltage: A battery voltage of between 11.4 and 14.5 V is required for the following troubleshooting procedure. This must be checked and provided, if necessary. On the vehicle electrical system, the voltage to the fuse (input side) must be guaranteed.

DIAGNOSIS/TROUBLESHOOTING PROCEDURE

Work instruction			Display OK	If not OK
1	Visual inspection	Switch off ignition Check plug connection at potentiometer signal for seat belt height adjustment on driver's memory seat adjustment control unit for damage (corroded or bent pins)	Go to Step 2	Repair plug → End
2	Check supply voltage of potentiometer seat belt height adjustment	Pull plug P off the driver's memory seat adjustment control unit Switch on ignition Measure voltage between pins 2 and 3 of the driver's memory seat adjustment control unit. To do this, actuate the seat belt height adjustment	approx. 12 V Go to Step 3	Go to Step 9
3	Check potentiometer for seat belt height adjustment	Pull plug off the seat belt height adjustment Measure resistance between socket pins 3 and 5 Measure resistance between socket pins 3 and 4 Move seat belt height adjustment mechanically from stop to stop	0 to 10 KΩ Go to Step 4	Go to Step 8
4	Check wires from driver's memory seat adjustment control unit to potentiometer for seat belt height adjustment for short circuit to ground	Switch off ignition Pull plug P off the driver's memory seat adjustment control unit Pull plug off the seat belt height adjustment Measure resistance between pin 2 of control unit plug P and ground	∞ Ω Go to Step 5	Repair wire → End
		Measure resistance between pin 3 of control unit plug P and ground
		Measure resistance between pin 5 of control unit plug P and ground
5	Check wires from driver's memory seat adjustment control unit to potentiometer for seat belt height adjustment for short circuit	Measure resistance between pins 2 and 3 of control unit plug P	∞ Ω Go to Step 6	Repair wire → End
		Measure resistance between pins 2 and 5 of control unit plug P
		Measure resistance between pins 3 and 5 of control unit plug P
6	Check wires from driver's memory seat adjustment control unit to potentiometer for seat belt height adjustment for open circuit	Measure resistance between pin 2 of control unit plug P and pin 4 of potentiometer signal plug for seat belt height adjustment	< 5 Ω Go to Step 7	Repair wire → End
		Measure resistance between control unit plug P Pin 3 and seat belt height adjustment potentiometer signal plug Pin 5
		Measure resistance between pin 5 of control unit plug P and pin 3 of potentiometer signal plug for seat belt height adjustment
7	Check wires from driver's memory seat adjustment control unit to potentiometer for seat belt height adjustment for short circuit to B+	Switch on ignition Measure resistance between pin 2 of control unit plug P and ground	< 0.3 V → End	Repair wire → End
		Measure resistance between pin 3 of control unit plug P and ground
		Measure resistance between pin 5 of control unit plug P and ground
8	Replace seat belt height adjustment		→ End
9	Replace driver's memory seat adjustment control unit		→ End