P0505 1995 c280 - PeachParts Mercedes-Benz Forum

georgeb · #1 09-17-2008, 01:33 AM

Car is in great condition with 120,000 miles and of coure next month is inspection. One day last week I started the engine and it reved fairly high and settled down right away. The car ran fine but the idle was high at about 1100 rpm. I cleaned the throttle body thinking maybe it was getting stuck and it seemed to be fine, started normal and idled normal. I reset the cel and after taking it on a long run I was on the highway and the light came back on. I felt the throttle acting a little funny like hesitating a little. Checked the codes and a P0505 showed up. I have no idea what this means or where to begin looking. Could the electronic throttle body be bad?

mbdoc · #2 09-17-2008, 08:21 AM

Do you have any other computers scanned??

Possibly a code in the traction system OR the electronic accelerator?

georgeb · #3 09-17-2008, 10:50 AM

I only have the ability to pull obd codes. Do you know how many seperate systems there are and who has the ability to read them? Is this a mercedes dealer shop only type of thing and if so what would they charge just to read the codes on average? Thanks

georgeb · #4 09-21-2008, 12:17 PM

I would appreciate it if someone could share their experiences with this diagnostic code 505. I'm sure i'm not the only person here who has had that problem. Thanks

deanyel · #5 09-21-2008, 01:23 PM

Code 505 is "idle control system malfunction" which raises more questions than it answers. Are you sure that's the only code your're getting? This is presumably from the OBDII port under the dash. Have you tried reading the codes from the 38 pin connector in the engine compartment? We need Arthur or Doc here - can he not read the OBDI codes with a flash code reader on the 38 pin on a dual system (OBDI and II) car like this?

georgeb · #6 09-21-2008, 03:34 PM

That is from the obdII connection. I didn't think I was able to pull codes from the 38 pin connector. 505 is the only code it threw so far.

deanyel · #7 09-21-2008, 04:00 PM

I think you can but not sure. The Baum fault code book certainly shows OBDI code lists for a 1995 202 chassis.

Douge · #8 09-21-2008, 06:05 PM

You likely have a faulty throttle actuator. I had an identical problem on an E class (same fault code) and it is very common. Bad news is that it is an expensive part. I was able to find one at a recycler and still paid $350 for it. They are 1k new. Its and an easy DIY though.

georgeb · #9 09-22-2008, 12:32 AM

Dean ty i'm going to look at trying to build one of those readers for it. I was under the impression that it was either a digital or an analog readout on the computer. I didn't think you had both.

I sure hope its not the actuator. Can those be rebuilt or is it just a replacement part? I thought I saw some info on here one time about someone rebuilding one.
I better check the wiring too come to think of it.

deanyel · #10 09-22-2008, 12:49 AM

Rebuilt throttle actuators are available. But that code is a general code that covers a lot of territory. On OBDI that code is simply telling you to check the CC/ISC socket for more detailed codes. The throttle actuator is an expensive enough part to justify some further code reading, and seeing what you can get on the 38 pin connector is a good place to start. I have a vested interest in the question as I recently bought a 95 S320 which is also a 38 pin / early OBDII adopter, as is the 95 SL320.

georgeb · #11 09-22-2008, 10:54 PM

I was able to pull codes from the 38 pin diagnostic connector for the cruise control/idle speed control computer and I got codes 3, 5 and 11. Code 3 says cruise control/idle speed control actuator, 5 is stop lamp switch, and 11 is Fuel safety shut-off to LH-SFI control module. Is there a way I can narrow this down any more.

deanyel · #12 09-23-2008, 01:25 PM

So it looks like the 1995 early OBDIIs are also OBDI flash code reading. Nice to have both.

georgeb · #13 09-23-2008, 07:59 PM

Yes its nice to have both. I erased the 505 code and tried erasing the other codes. The 3 error code will not erase no matter what I do. I drove the car and the CEL came back on and the idle is now high. In nuetral its around 1400 as opposed to about 650 normally.

georgeb · #14 09-24-2008, 04:07 PM

i decided to try the other pins to see if there were any more codes and on pin 4 i pulled a code 8, Idle speed control (ISC) system at upper or lower control stop or CC or EA indicates "limp home" mode.

georgeb · #15 09-27-2008, 09:14 PM

I decided to pull the eta out and have a look at it. So far I've removed the intake and the rubber boot connected to the top of the eta. There is a black thing that sits on the intake I believe its called a resonance flap. I removed four allan bolts from that and the top piece came off but the bottom of it is sitting in the intake and I can't see whats holding it on. It looks like a diaphram of some sort. Can I just pry this thing out or is this connected to the intake somehow? By the way what is the purpose of this part?

Nevermind it just pops off. I'm going to open up the throttle body tomorrow to check the wiring.