Fault code 2566: Diagnosis/troubleshooting

NOTE:

When troubleshooting, the status of the fault must be observed!
Use a suitable test cable or a trailer, which is definitely OK, to check whether the fault is present on the vehicle.

DIAGNOSIS/TROUBLESHOOTING PROCEDURE

Work instruction			Display OK	If not OK
1	Connect test cable or OK trailer (tool) to trailer socket and check whether functions are present or whether the fault occurs again		Fault exists in trailer; repair light, plug connection or wiring. → End	Go to Step 2
2	Check fault memory in the trailer hitch control module for [F8] fault		'Open circuit' 'Short circuit to ground' Light is not lit Go to Step 3 'Short circuit to B+' Light is lit continuously Go to Step 4
3	Check wiring in vehicle between trailer hitch control module and trailer socket for an open circuit	Switch off ignition. Pull off plug A on trailer hitch control module. Measure resistance between pin 7 of plug A on trailer hitch control module and pin 1 of trailer socket.	< 5 Ω Go to Step 4	Repair wiring or replace wiring harness. → End
	Check wiring in vehicle between trailer hitch control module and trailer socket for a short circuit to ground	Check resistance between trailer socket, pin 1, and ground.	∞ Ω Go to Step 4	Repair wiring or replace wiring harness. → End
4	Check wiring in vehicle between trailer hitch control module and trailer socket for a short circuit to B+ (see note)	Push plug A on to trailer hitch control module. Switch on ignition. Check voltage between trailer socket, pin 1, and ground.	< 0.3 V Go to Step 5	Repair wiring or replace wiring harness. → End
5	Check ground leads	Measure resistance between trailer socket, pin 3, (pin 2 in North America) and vehicle ground.	< 5 Ω Go to Step 6	Repair wiring or replace wiring harness. → End
6	Replace trailer hitch control module		→ End