I am a new Mercedes owner having recently purchased a 2001 ML320, 58K about 3 weeks ago. Everyone in my family and I until this point have been BMW drivers...they now call me 'The Defector"

Soon after purchasing the brakes lights came on. After checking it was decided the front brakes are still pretty ok but the rear brakes are ready for a brake job. I have continued to drive the car hoping to get my hubbie to perform the needed maintenance soon. Anyway last night after driving about 300 miles I put the 320 in park to go into the gas station and when I returned I could not get it out of park....started fine...no warning lights. I panicked...small town in south Missouri... alone and late at night !! Got out the handy manual...stuck the ball point pen in the shifter and took off. Got home, garaged car and stuck again in park.

Help...is this related to the brakes??? I thought possibly it didn't want me to drive it until I changed the brakes?? Any ideas? Thanks for any help anyone can offer.

 

Hi,

The PRND selector problem is not linked to a problem with the brakes not stopping you but quite possibily there is a link to the brake malfunction light. The brake may however still need to be attended to (new pads etc) as a separate issue.

Not completely familiar with ML but the brake malfunction light may be advising a problem with the rear end brake lights not working.

The solenoid which controls the PRND selector has an input from the brake light switch to ensure that you have your foot on the brake prior to putting the vehicle into gear.

You did well to overcome the PRND problem with a biro. Not many people bother to read the manual.

Now check whether the rear lights come on when you press the brake pedal with the ignition turned on. Maybe the footbrake switch requires replacement (contact arcing) or adjustment.

Keep us advised.

Stuart

 

Thanks Stuart

After reading your reply I checked the car and I did have brake lights...so I thought about what you wrote for a bit, went back to the car, started it and pushed the brake pedal in harder than I normally would. Alas, the car went into gear. I believe the brakes are bad and the car is not sensing my foot on the pedal. I have continued to drive with no problem, as long as I'm pressing hard to put in gear, but I know I will have to get the brake job pretty soon.

Thanks for your help. I'll get the brakes done this week. I like the mercedes....it's pretty zippy and I like the ride. Deb

 

Hi Babydoll!

All that is necessary is that the brake light switch is replaced, adjusted or shimmed as necessary.

There should be nothing wrong with the brakes themselves.

Glad we got your problem sorted out.

Stuart

 

It turned out the rear brakes were worn to the point that the wear indicator was touching the rotor giving an intermitten signal to the ECM. The computer interpreted that as an ongoing unsafe driving condition and tried to lock the transmission in Park. Now that the brakes have been replaced the problem has vanished. The brake pads were original. Thanks for your help.

 

Interesting!

I was unaware of any linkage between between the pad warning system and the transmission interlock. However there is always something new to learn.

However, if the ECU was causing the interlock due to the brake pad wear warning device I don't see why pressing hard on the pedal would have overcome the interlock.

I don't doubt the interlock problem appears to have disappeared but I wonder whether any linkage to the rear brake job does infact exist.

Changed fluid level with new pads? The same argument exists.

I'm glad that everything now seems to be back to normal.

Anybody else have any information about possible system linkage?