tap1369

Hi,
I recently acquired an 2001 Mercedes S600. It spent the last 2 years on various parking lots, and the last owner neglected it in a big way!
So - it is a project.
Currently I am having this red warning message on the dashboard:

Brake service
BRAKE
Stop, Call Service



accompanied by ABS light and code 0120 - accelerator pedal sensor circuit A error, resulting in some kind of LIMP mode - car wouldn't run more than 2000 RPM and more than 30MPH downhill.

Here is the sequence how it all happened:
1. I got regular message for brake wear and I changed the front rotors, sensor wires and pads (with cheaper ones from Rockauto);
2. I drove the car for 17 miles and felt some skip (jerk) between 60 and 70 mph - I believe that produced the 0120 code - pedal sensor fault;
3. I changed my 4 tires that same day.

After changing the tires, driving out of the tire place, I got the red message, turned around, told the guys and by the look on their faces understood that they wouldn't be able to fix it. So I drove to my mechanic - down the street.
He reset the computer, light went away for about 2 miles and came back. I drove home limping and that was 1 week ago.
Since then I am trying to fix it.
Here is what I have done so far:
1. Changed the rear rotors, pads and sensor wire;
2. Installed new gas pedal;
3. Replace the brake light switch
4. Checked the tire pressures and adjust them to spec (found front left tire to be around 50 PSI)
5. Reset with OBD2 cheap scaner
6. Tried to reset ECU 2min with gas pedal down, 5 min contemplating thing
7. Reset Comand - Mute+1+3
8. Drove the car around the block

Now I am running out of ideas, and that's not good!
Please share with me your thoughts and advice me what to do next!
I am aware of the Dealer ability to hook the car to Star Das - but that would be my last option.
Thanks!
Best Regards!

Welwynnick

Brake fluid level?

Your mechanic is the key.

He re-set the light, so he would have seen the fault code that tells you what's wrong.

Re-setting the light isn't a solution to anything.

Nick

tap1369

Hi Nick,
Yes, I checked fluid level before and after replacing the rotors and the pads. As the rotors are new - thicker and pads as well, level went up, so I drained a bit to bring it to where it needs to be.
Brakes work fine, not soft, not hard, vacuum booster gets vacuum, sensors disconnected and reconnected, ABS speed sensors removed, visually inspected and cleaned...
And here I recall something I did wrong!
When my front was lifted for rotor replacement, and calipers were hanged, I pressed on the brakes by mistake. It is possible, that i managed to introduce air in the system. Let me check that! I would try to flush the system today.
Thanks Nick!

Welwynnick

Had you pushed the pistons back when you pressed the brake pedal? When the pistons are fully retracted, it takes several pedal strokes to push them back out.

If there's a problem, you would be able to see fluid around the piston seals. I think you're probably OK, just don't do it again! Likewise, don't turn the steering wheel if you happen to have that disconnected.

The message is a mystery, as I haven't seen it before, and I haven't seen it any owner's manual. You need to know the code. If it's the brake pedal switch, bear in mind that there are two switches, not one.

The brake light switch, fluid level sensor and pad wear sensors are the main culprits with brakes. ABS is more complex, and I don't know much about that on Mercedes. In general, if you have an ABS fault, it's down to the wheel speed sensors or their wiring. Anything else is difficult.

Nick

tap1369

Hi Nick,
Thank you for pointing my attention to the brake fluid!
It is obvious "now", that I caused the whole issue - introducing air in the system. Yesterday I flushed it, and I got some air out, but not all of it. It seems that the ABS setup is tricky to be purged.
Smart people are using computer to activate the ABS pump, and some (not so smart) - use more fluid, time and pray for mercy on their ride.
So, after the second flush, and my wife pumping the pedal - success! ABS light gone! Ugly red warning - gone!
Now the pedal code 0120!
Guess what - I caused this one too!
During the deep clean that the engine needed badly - I disconnected and removed the air mass flow sensor. I was checking the connections and seems I left the connector to the throttle accurator kind of loose. When I pressed it today, it clicked - fully engaged - locked. And the pedal started working again!
Now the car revs like tired tiger and only needs tons of other attention...
Starter, hydraulic system flush, strut mounts, soft close / central locking, ...
So far - so good!
Thanks again!

tusabes

Anytime a problem
develope after working on a car always go back and retrace all the work

as something usually wasn't put back correctly