We bought our ML500 new back in 2002 and it has had all of the usual W163 problems, mostly sorted out in the first 5 years.

It's got 220,000km on it now and has been suspiciously well behaved since I took it out of the clutches of the stealership who were inclined to bit generous in recommending things that needed to be done.

It's been ultra reliable and only let us down once when the CPS failed (see my post on how to replace it)

The brake pedal switch was replaced, probably, 8 years ago. The windscreen washer reservoir was replaced years ago when it cracked ( it was probably leaking water onto the ABS pump for a while and there are some rust- like stains visible under the ABS pump motor when viewed with the wheel liner removed.)

About five years ago it developed an intermittent issue where the Yellow BAS/ESP, ETS, ABS warning lights would come on once or twice a year always on the coldest days at the bottom of our driveway. Turning the ignition off and back on again put the lights out till next year

About a year ago the lights started to come on intermittently, maybe once a month usually at the bottom of the driveway after driving down 40m from a cold start but also at random other times.

When the car was serviced back in July my independent service guy Ross Firth from City Star Motors in St Peters Sydney (Nice guy has looked after our cars for 20 years) mentioned that the lights had come on during the test drive and a fault code C1025 - 003 was stored "Fault in CAN communication with control unit N47-7 (ABS control module). If no customer complaint exists the fault can be erased"

He erased the fault and the lights stayed off for a week then returned most days at random times and could be extinguished by turning the ignition off and back on again.

After checking various forums I removed the headlight and examined the wiring harness for chafing (none) and removed the front section of the ABS unit to check for cold soldered joints and for the connection to the pump motor.

I wasn't able to detect any high resistance solder joints. I cleaned up the contacts to the ABS pump motor.

The lights didn't come on again in the first week and stayed off till 4 weeks ago

The SDConnect4 and DAS software that I have used for the last three years to connect to the ML and SL55 decided to die on me which was a bit annoying

The replacement I ordered from another chinese vendor, who will remain nameless for the present, arrived within 5 days but, despite numerous attempts has failed to connect to either car.

In the meantime I have swapped over the ABS pump relay and bridged the relay connections to ensure that the ABS pump motor runs ( it does every time the ignition is switched on with the relay contacts bridged)

I have removed the wheel arch liner and disconnected the wiring harness, cleaned the apparently clean contacts, sprayed contact cleaner around

And the lights keep coming on randomly. Sometimes they extinguish after turning the ignition off and sometimes they don't.

The lights can come on after a 3 minute drive, they are never on when starting from cold. Sometimes they come on turning a corner, sometimes they turn on driving along a straight road after driving for 30 minutes

On two occasions in the last three weeks the lights have come on and then the brake warning light and warning chime goes off at anything over 25km/h. I understand , so the manual says, that this indicates a fault in the electronic brake proportioning module.

The domestic goddess, who is the regular driver, is beginning to get a bit worried about her safety by now.

With a trip away planned in the New Year and the emails going backwards and forwards to China about the SDConnect going nowhere I took it to Ross this morning. It's not often that I need to look for outside help and I thought that my diagnostic approach so far had reached a dead end

There were 5 faults stored:

C1025-003 as mentioned above
C1202 A7/7s1(BAS release switch) plausability
C1300 A7/3y6 (Front left solenoid valve, hold pressure)
C1401 A7/3m1 (High Pressure and return pump)
C1314 Component A7/3 (Traction system Hydraulic unit) Test voltage supply of solenoid valves.

Ross erased the codes and then took the car for a 30 minute drive... no lights, then a 20 minute drive... no lights then another drive and the lights came on.

The codes stored were the same as above and they cannot now be erased

Not being one to throw expensive parts at the car like the dealer he is inclined to send the module off for testing but with Xmas only two days away and everything shut down for a week after that I thought I would run the problem past the global expertise to see what suggestions might come up

Thanks for reading

Peter
Sydney, Australia

 

I conclusively tracked down my intermittent BAS ESP/4ETS lights flashing and Brake Malfunction beep/Transmission in Limp mode issues to

F22 : 15A : Traction control/cruise control/transmission/instrument cluster
F27 : 40Amp : ABS Hydraulic Unit

F22 for sure was oxidized..and I guess, it would have built up higher resistance causing intermittent low voltage error codes on Pin 87 of the ABS relay..

Problem has completely disappeared after replacing the 2 fuses.

I would advice all on watching out for these fuses on aging MLs...they may be intact, but their resistance parameters could have changed significantly after all these years..causing strange an intermittent electrical faults.

 

I THINK THE PROBLEM MIGHT BE WITH THE "STEERING ANGLE"

 

The smoking gun is code C1401 which means the brushes in the Hydraulic Pump Motor have worn down. Link is supplied for brushes needed and should be obtained before removing the motor.

Refer to the link below to remove the motor. Remove left front wheel and fender liner. Then remove the two screws holding the motor in place.

Having a long screwdriver at hand, slowly withdraw the motor and make sure the cup behind the motor does not come out with the motor.

http://www.benzworld.org/forums/w163...ghts-come.html