95 SL500 ODBII Location? - PeachParts Mercedes-Benz Forum

beerme · #1 10-26-2004, 10:01 AM

Hello All,
My CEL has illuminated on my 95 SL500, I have had the car for about 3 weeks now and the car is running fine. I think it has to do with the fuel I put in the car but am unsure. I run strictly Super Unleaded which is what is recommended, however I primarily run Shell fuels. I have experienced this behavior before with other makes of cars when I would switch between fuel brands so I am guessing the previous owner used a different brand of fuel. My question is where is the ODBII connector located? Owners manuel says on firewall but that didn't help me find it. Can anyone give me specifics on location please? Finally to clear the code will disconnecting the Negative side of the battery only do the trick?

G-Benz · #2 10-26-2004, 11:11 AM

I need to get an SRS code cleared on mine, but sorry, I haven't found it either.

As to your second question....stored codes are not reset when disconnecting the battery...you need an ODBII scan tool to do this. Believe me, I've tried...

bobterry99 · #3 10-28-2004, 07:17 PM

I've never worked on a '95, but I believe it is not OBDII compliant. The diagnostic connector is round and located on the passenger side near the firewall.

To erase a code, you must first read it. I suggest getting a diode from Radio Shack with a built-in resistor for less than $2. It is P/N 276-209. Connect the anode (+) of the diode to socket #3 of your diagnostic connector and the cathode to socket #4. Then use a wire to short socket #4 to ground for 2 to 4 seconds to trigger a code read. You can use socket #1 of the diagnostic connector for your ground.

While the short is in place, the LED will be on. When you remove the short, the LED goes off for a couple of seconds and then begins to blink-out a code. Once you have the code, wait a couple of seconds and then short socket #4 to ground for 6 to 8 seconds. Repeat until you have read and erased all the codes.

Regarding the SRS, from MY '94 and later codes may only be reset using Mercedes Hand Held Tester or similar scan tool.

beerme · #4 11-02-2004, 03:43 PM

Ok, I think I have found my OBD connector on my 95 SL500 but I have a question. Would this connector be considered an OBD1 style or is it proprietary? The reason I ask is I tried following your instructions in the previous post but I found a unique problem. The connector I located had a round socket so I couldn't locate pin #1, the electrical connector I located was under a black plastic cap that resembles a radiator or gasoline cap w/exception it has a hex nut in the cap and is located on top of a gray metal box infront of passenger side windshield/firewall area. The connector is about 1 - 1.5 inches in diameter, if this is the correct connector how do I locate pin#1? If this is a standard OBD1 connector then I should be able to go to local autozone and have code read and reset for free.

Thanks for all responses in advance.

Phil

RickM · #5 11-02-2004, 04:58 PM

This will tell you if you have OBD-II: http://www.obdii.com/connector.html

And here's all you want to know about OBD-II: http://www.obdii.com/obdii.html

BTW, OBD-I used a 12 pin connector as opposed to a 16 pin config for OBD-II. However, some car manufactures used the newer 16 pin connectors with OBD-I (wired differently inside the socket) during the 95-96 transition period.

RickM · #6 11-02-2004, 05:06 PM

I believe that both I and II are standards that are used universally. This from GM:

beerme · #7 11-02-2004, 06:05 PM

Okay,I thought I had located the correct connecters, there was a number 2 on the connecter which I assumed was pinout 2's location. Bottom line is I was able to make the led flash according to the above description however I cannot locate a valid code definition for the car. According to Jim F's page code 15 isn't used, I read the code 6 times with the same result and the error condition never cleared which leads me to believe I do not have an erroneous code but rather a problem.
After looking at another image at Jim's website I found that I was not on the correct pins, so I relocated and retested from what was the correct pin locations I think. Anyway at that location I got a code 1 which is still a bad code from what I can tell, regardless it didn't clear. Also on that set of pin outs when the key was off the led would still light up, that made me a little concerned. At this point I welcome each of your expertise and advice, though I am starting feel like a trip to the shop is in my future.

Phil

bobterry99 · #8 11-03-2004, 02:55 AM

A single pulse indicates no faults are present, Phil. Not sure, but your car may have a Diagnostic Module which is turning-on the Check Engine light. I suggest checking socket #19 for faults.

beerme · #9 11-04-2004, 07:15 AM

Bob, I apologize for being stupid with this question I am just very timid about possibly shorting my computer out. How do I check pin# 19 as you suggest? Do I put the led + in pin 19 and - in pin 20, then ground from 1 to 20? Thanks for your assistance,

Phil

bobterry99 · #10 11-04-2004, 12:54 PM

When you are checking a system, the anode of the LED is always connected to socket #3 and the anode is connected to the socket which corresponds to what you are reading, and that socket is shorted to ground to trigger a read.

So in this case for the Diagnostic Module, connect the anode (+) of the LED to socket #3 of your diagnostic connector and the cathode to socket #19. Then use a wire to short socket #19 to ground for 2 to 4 seconds to trigger a code read. You can use socket #1 of the diagnostic connector for your ground.

beerme · #11 11-04-2004, 01:07 PM

Great, Thank you very much BOB. You have been a big help and I am very grateful. Cannot wait to get home and see what the code is.....

Phil

beerme · #12 11-04-2004, 07:00 PM

I retrieved the code which was a 26 however in the process of removing the ground I caught and shorted the two pins. ( I had a feeling I was going to do that) Ended up blowing the fuse on that Luckily, because my dash was possesed. Anyway I am not sure I am reading Jim's page correctly, I did pull a Code 26 which from what I found is a Upshift problem. That makes sense because I did hit the gas hard showing off for a friend of mine. If I am not reading the code correctly please let me know, also is this something I really should worry about?

Thanks again for all of your help....
Phil

bobterry99 · #13 11-05-2004, 12:19 AM

Phil, the upshift delay is a feature designed to enable the catalytic converters to warm-up faster. Many people consider it annoying, and I have it disabled on one of my cars. If yours has a problem with the delay, I would not be at all concerned about it, but it will keep the CEL on.

One note. If the problem is active you should have the same "26" stored in the fuel injection controller which you checked through socket #4. Since you found no code there, it may be that the problem has gone away. Codes from the FI controller have the ability to clear themselves if the condition which triggered them disappears...I don't think this is true of the Diagnostic Module's codes, as I think they have to be cleared manually.

beerme · #14 11-05-2004, 06:17 PM

Thank you very much Bob, your help saved me a service trip. You ever make it to Central Florida I will buy you a beer.