Yesterday my 2002 C32 suddenly almost died on the road, would only limp along at about 10-12 mph. Dash said ESP error. Put my OBDII code reader on it when I got home and got P0120.

Reading various posts here as well as other sites it mentions most likely cause being throttle peddle sensor which means replacing pedal assembly ($250) I tried the throttle pedal reset (hold pedal down for 1 min. while key in position 2) but no change.

Also mentioned were possible throttle body issues such as loose/coroded connector or dirty/bad throttle body. Before popping $250 for new pedal assembly, I decided to check the throttle body/connector. Connector looked good, cleaned with electric connection cleaner, added a little dielectric grease and made good connection.

Throttle body looked a little dirty, so I pulled it and cleaned. When I went to reinstall, I noticed that the y-shapped vaccum hose that connects to the bottom of the throttle body had collapsed on one side with big slit opening.

Since this definitely needs replacement, I ordered one ($92).

My question - Is this the most likely cause of my P0120 code, or am I likely to still have issues after it is replaced.

I know that I should probably get it to dealer to read with Star diagnostics, but car is undrivable (I don't want to drive across Houston at 10 mph) and tow would be $100. Even if I replace both the pedal assembly and then have throttle body rebuilt, it would be less than tow to dealership and pay for their repairs. Just want to make sure I follow the most likely items first.

 

Check this thread, posting, worked for me....

https://mbworld.org/forums/5250601-post53.html


Good luck!

 

Had the same code/problem, after doing the same work on my car, just this weekend. Any chance you still have the part number of that Y-hose? I'm not sure if it's actually a vacuum hose or not (I was thinking it was a drainage hose for oil buildup in the TB to the heads), but I literally had the same torn tube inside the hose when I took off the TB.

https://mbworld.org/forums/c32-amg-c...hose-tube.html - my thread, hopefully some answers for you in there as well. The P0120 code points to so many different culprits - TPS, pedal assembly, TB wiring, engine wiring harness, fouled IAT.

 

I had to replace my throttle pedal assembly. I ordered from MB of Monterey for 136.00. However my symptons were different. I had delayed reaction from the pedal about 2 secs. Then after a few days no response at all. Changed the assembly and all back to normal.

 

 

Awesome! Glad to hear it's working as intended again. Any chance I could snag the part number for that y-tube, though?

 

That's a pretty good price for a stealership.
My symptoms are engine goes limp after an initial full pedal depression ( car takes off like crazy). Any hard acceleration after that, the car goes almost immediately limp. I know it's not my IC pump. And if you kill the motor, it resets itself but you would only get to do it over once only and then goes limp again.
Was this a DIY job? What's the difficulty level and how long did it take to replace?

 

60n -
Possible causes:
Pedal sensor (easy to replace)
TB Actuator (more involved)
The TB actuator female elec pin connectors (these get tired/weak/loose after a few disconn/reconn and give intermittent faults). $36 in parts @ MB for the connectors.

I would hook up star to help diagnose.

GL.

 

Doug,

U ever pull any codes? Man, u really need to get this taken care of, sounds like it's been going on for a while...

Sometimes, even though there's not a CEL, u may have stored hidden codes that can be pulled to help point you in the right direction.

 

Betezra, would a stealership be able to get the part number for the electrical connectors on the TB actuator? The wiring harness that goes directly to it has another connector about a foot down the line, so I figured I could just order that a new version of that last piece and call it a day, but I called three and they had no idea.

 

Read post#41 in this thread:

https://mbworld.org/forums/c32-amg-c55-amg-w203/451878-ruh-roh-raggy-p0120-2.html

 

Awesome, thanks! Is it the same connector even though that's from a C55, though?

 

I'm 99% sure it's the same connector, because I believe both cars use same TB.... 74.5mm.

 

Yep, that sounds right. Looks like I'm off to the dealer tomorrow! Cannot thank you enough

 

91rs did the heavy lifting in his c55.... my clk55 used his info.... and now your c32 the same thing...... now we need an ml55 or s55 to pop in for the fix LOL>

GL>

 

Betreza,

I agree with your diagnosis. The key question is how to narrow down the choices. It seems to me that all three are directly related and I doubt a Star tool reading would differentiate. Pedal sends signal, cable transfers signal, TB actuator receives signal and triggers TB to open/close. A break in any one of these it seems to me would cause the same code and problems.

As stated in my first post. Car can only idle and creep along at 10 mph, so getting it to dealer to have star read would involve $100 tow. Then I either pay through the nose to have them repair or pay to have car towed home.

So if it is one of the three above I would like to start with the most likely. Most posts I have read at other web sites point to pedal assembly, with a few also saying Throttle Body.

Only one guy seems to be pushing for cable connection as the cause and he appeared to have a modified car that had the cable pulled and replaced numerous times, thus causing the eventual loose connection. Although this is a low cost item, it is not an easy repair. Either buying a complete new cable/housing and trying to run it down through the engine bay. I tried feeling my way along cable and could not trace it beyond about a foot from the TB connector before it disappeared into very tight spaces. This cable looks in very good condition, makes a solid snap connection and has not ever been removed my me. If it was removed by dealership, it would have been at least 30,000 miles ago (supercharger/intercooler issues)

If we look at the TB actuator, are we talking about having the entire Throttle Body replaced or rebuilt? I have heard people mention TB rebuild, so if so, where do I go for TB rebuild?

 

Evilsaint,

I am going to pick up y-hose from dealer in a couple hours and will let you know part number.

It sounds like you are going with the replace cable idea as your repair option. Can you tell me why you chose this option?

Are you going to replace the entire cable including connectors? You mention it connects about a foot down the line. Where is this other connector and how do you access?

 

The connector at the TB was the only thing I had any trouble getting off the car while removing the TB to clean it the other day and the connection itself is quite a bit loose now that my fat fingers half-broke some of the plastic while taking it off initially. Also, I've noticed that when I got a good fit back onto the TB connector, after spraying it with some electrical contact cleaner, my issue (surging revs at idle in neutral/park) got much, MUCH better (idle jumping from 1.2-1.4). I did a comparison and plugged it back in as loosely as possible but with the connections still fully "in", and the problem was much worse (idle jumping from 1.1-1.6k or higher).

It still sounds like a vacuum issue to me but I've checked all of my vacuum lines and they're all pristine and hooked into the right places, plus, I never removed any of them.

The second part of the cable is about a foot and a half down the wiring line, tucked down in back of the engine under the y-splitter and TB, and hitched into the same line with a larger connector, almost like they anticipated the throttle body connector wiring going bad... Once you take the y-splitter off, there is a good foot or two of loose cabling post-TB connector that gets tucked down next to the firewall; that's where the second connection exists on mine. I'll get some pictures once I get the parts, but that may not happen until Saturday. Just give it a light tug once you have the y-splitter off and the cable should come up out from the depths of the cavern between your engine/firewall.

I'm pretty damn sure now that's the right part number, or the same connector at least, since the W112 (our engine) and the E55/SL55/CLK55 engines utilize a lot of the same auxiliary parts in other places as well. Hell, my replacement SAI pump came from an E55, and I almost replaced my SC coolant pump with one from an E55 as well =)

 

When I replaced my intercooler and had the whole sc assembly out, I tried to trace the TB connector to no success. If I remember correctly, the connection went missing into the abyss.

Good luck and keep us updated.

 

Hi Betrezra. Could you please explain how to change the TPS (Pedal Sensor). I'm about to replace mine and I wanted make sure I'm ready and there are no surprises. Or is it pretty self explanatory once I get in there under the pedal?

I've gotten a couple of limp mode instances during kickdown (this was PRE-blower install).

Thanks in advance.