MU-X Engine warning light


New Member
This light came on whist towing my caravan yesterday. Car went into limp mode. Turning vehicle off for a minute or two would fix the limp mode but the light remained on, and the car would revert to limp mode again in a short time.
Searched this site and discovered that the blue reverse light cable at the seven pin plug sometimes can cause the problem, although not connected to the caravan.
Disconnecting the reverse light wire fixed the problem.
I have towed this van since buying the MU-X new in 2017, for over 30000ks.
There were about 2volts only at the seven pin plug on the reverse light cable with the car reverse lights on.


Well-Known Member
The blue wire is for the caravan brakes. The reverse lights are the black wire and is not normally used on a caravan or trailer. If you disconnect the blue wire, you will not have caravan brakes.
If you are going into limp mode it is commonly caused by an earth fault in the trailer plug which you appear to be experiencing. It often causes the brake light fuse to blow. Look in the fuse box under the driver’s side of the lower dash.


New Member
Thanks CTL. Reconnected the blue wire and checked trailer earth wire, which was loose. All seems o.k. now.