W163 ML350 BAS/ESP/wiring issues (fuel pump, Wheel speed sensor & brake wear sensor)

[basharv]

I have just had fun and games with my 2003 ML350. A few weks ago, it would turn over and not start. I had mobilolife come out who did a star diagnosis and could not find anything. £200 later and it was diagnosed by a good independant as a fuel pump fuse failure (having checked the wiring charts, and done more tests).
I then drove it for a few days and the fuse went again. A neigbour and I then checked the cabling (continuity tests etc) between the fuse and the fuel pump connector (under the rear seats) and the cables seemed OK. A new fuel pump later (another £200) and it all seemed OK for a day when the brake wear sensor light came on. As the two faults appeared to be on separate circuits I got a new set of brake pads and fitted them (another £100) - admittedly I would probably have had to change them fairly soon anyway.
Then the next day I had the ABS/ESP lights (all three) and the Check Engine light come on. Not a very happy person at this stage, so I went back to the MB independant who found a wheel sensor code on the rear left wheel (RHD). He also had a code for the same wheel sensor jumping !! I booked it in for later this week and did a trawl of a few forums to see if there was another explanation.
I found one that suugested a wiring problem just back from the connector for the wheel sensor. I took the rear wheel off and traced the cable back and found the loom had been rubbing against a u bracket secured to the chassis in the wheel arch. It had gone through the binding and when I stripped the binding off, the fuel pump cables, wheel sensor and brake wear sensor cables were all in the same loom hence the various warnings/faults etc. I now have an auto-electrician repaining the cables probably for less than £100.

Hopefully this saves someone else from a huge bill

 

[television]

Thank you for your post, it is rare these days to have actual wiring faults, and diagnostic tester cannot cope with such faults very well. They normally say things like X cannot communicate with Y leaving you with no choice but to replace an expensive component and hope that it solves the problem. With a long study of the wiring diagrams it does in some cases like yours show that there is a common link.

This was good work on behalf of your indie and your self.

I have stored your post, in case it can help someone else, and thank you again for the post

 

[basharv]

final comment

The electrics were done today, the cables in the loom were completely frayed. They have now been soldered and jointed and the various lights are all cleared. Whilst the star system is great for picking up codes and giving pointers to problems, the diagnosis of problems should still be based on sound basic principles (helped by forums like this too!!).

 

[television]

The electrics were done today, the cables in the loom were completely frayed. They have now been soldered and jointed and the various lights are all cleared. Whilst the star system is great for picking up codes and giving pointers to problems, the diagnosis of problems should still be based on sound basic principles (helped by forums like this too!!).

You are so right on the diagnostic tools,,you do need to have some feeling as to what it is telling you, then you need to work out the plausible reason.