r129 - is this the beginning of the end

[R129mine]

hi

i drove along at around 70mph today in cruise control when all of a sudden cruise control stopped, the speedometer stopped working and the ABS, ASR, brake and handbrake light all came on at the same time

the mpg indicator also stopped working.

i stopped on a layby and stopped engine and started it again and still 4 ligths are one. when i drove off the gearbox seemed to be stuck in 1st or 2nd gear so i limped home last 3 miles.

see attached picture for the 4 lights

anyone any idea what could be causing this? electronics or gearbox also broken?

cheers
sorry was not sure which forum to put this in.

 

[Setanta]

I am gambling on the MAF + battery since sounds exactly like what was happening to one that I looked at. Replacing MAF and a new battery and a STAR reset put it all back to normal

 

[Diesel Benz]

I am gambling on the MAF + battery since sounds exactly like what was happening to one that I looked at. Replacing MAF and a new battery and a STAR reset put it all back to normal

Why would a MAF make the speedometer stop working?

 

[Dieselman]

I guess it's an ABS sensor fault.

 

[Deleted member 11979]

I reckon the battery is kaputt, it happened on mine, changing the battery sorted it

 

[Setanta]

Why would a MAF make the speedometer stop working?

MAF for lack of power, battery for the electrical items.

Speedo - no idea.

Overall, it matches almost one for one what I saw in another SL

 

[Deleted member 11979]

In mine the flat battery caused exactly these symptons, try another one before you go spending any money.

 

[R129mine]

I bought a new battery about 1 year ago but will check it out, in January of this year i replaced the alternator as battery stopped charging

maf is that mass airflow sensor? i guess i won't be able to replace that myself. will drop it off at garage on friday to get it checked out

 

[EDZ649]

MAF's are easy to change, takes about 2 mins. No point buying one before you know what the problem is.

 

[A210AMG]

Do they have speed wheel sensers?

could it be that.

If you can get it plugged into a machine and codes read hopefully its something easy (and cheap) to fix.

 

[kth286]

take car to Merc specialist that understands that model.

Get the fault codes read as car gone into limp mode.

 

[MD5]

As kth286 says, the Star diagnostic test should remove most of the guesswork. The brake pedal switch went on my 96 500 a few years ago, which disabled the c/c and kept various lights illuminated. I also had a coil pack go, which caused all of the instrumentation to flicker and misfiring, but not limp mode. Also, the alternator may have a problem at this mileage (mine did).

 

[R129mine]

it is booked in with pcs in Milton Keynes for tomorrow am, Mercedes Mk had no availability till Tuesday. i will let you know what happens

 

[swannymere]

it is booked in with pcs in Milton Keynes for tomorrow am, Mercedes Mk had no availability till Tuesday. i will let you know what happens

There's another PCS

 

[Indyz12]

I bet on an alternator fault. Not enough voltage going to the ABS computer will trip the light to come on which is linked to the ASR and some function of the cruise to determine the speed at the wheels.
Take it to a motor factor to determine if your battery is ok (if you got it from someone other than MB that is)
Other than that, MB will need to reset your gearbox computer so the fault codes get erased.

 

[Adam230K]

This could be the ABS sensor (isn't this attached to the differential?) or a wheel sensor (located near the brakes of each wheel). If you want to rule out of its the battery you can disconnect it for 5-10 mins and reconnect it to see if it makes a difference.

I really don't think its an MAF fault, as that would throw an Engine light, if anything.

 

[nick mercedes]

There's another PCS

Apparantly so, and since 1987:

PCS - Merc Index

 

[Setanta]

I really don't think its an MAF fault, as that would throw an Engine light, if anything.

I thought the same thing with the one that I saw but turned out it was the MAF. Really odd.

 

[BlackC55]

I doubt the MAF to cause this issue. They are normally 100% relaible on this 119 engine.

I suspect an ABS sensor or a voltage issue.

Get the codes read and all will be revealed.

 

[R129mine]

car back from garage.

it had a broken wire under the fuse box, earthing against body of car. it tripped the brake light switch and 15 amp fuse. once broken wire had been fixed and a new brake light switch car is driving fine again.
it took pcs quite a few hours to trace the fault to the broken wire (not easy to detect) but all is fine again