SL/R129: How do you get a CODE for the CHECK ENGINE LIGHT?
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From: Alexandria, LA.
92 500SL
How do you get a CODE for the CHECK ENGINE LIGHT?
I did a search and could not find my answer.
I have a check engine light and cannot find the plug for the OBDII computer.
What am I doing wrong? Is this one of those cars you have to count blinks or something?
I have a check engine light and cannot find the plug for the OBDII computer.
What am I doing wrong? Is this one of those cars you have to count blinks or something?
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Joined: Nov 2006
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From: Central VA (USA)
1999 SL500 Sport
Try this page; http://www.troublecodes.net/MB/
Last edited by RobsCountach; Nov 22, 2006 at 10:07 PM.
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From: Atlanta, unfortunately
'09 S600, (2) R129 300SLs, '03 SL500, '03 SL55
Reading Codes
The procedure described here works for all systems with diagnostics on the R129 through model-year 1995 except for the SRS (airbag) for '94 and '95.
Each system's diagnostic output signal is wired to a socket of the car's main "diagnostic connector", X11/4. An additional pair of sockets provide connections to battery voltage and chassis ground for convenience. Early cars with continuous-fuel injection have 16 sockets, while later models have 38 sockets. The sockets are numbered for easy identification. When you make connections you should know that all circuits have protected outputs and nothing can be damaged by mistakes.
The CE light is controlled by the Diagnostic Module on a '95. The socket for the DM is socket #19, socket #3 is battery voltage and socket #1 is chassis ground.
Codes are read sequentially one at a time. That is, you trigger the system you are checking to issue a code, you read the code, you trigger another code, and so on. With the key on and engine off, you trigger a code from a system by electrically shorting it's socket to ground for 2 to 4 seconds using a wire. A second or two after the wire is removed, a series of electrical pulses will occur at the socket. The number of pulses corresponds to the number of a code.
There are numerous ways to view the pulses for counting and getting codes. I use a $1.29 LED from Radio Shack (P/N 276-209) connected between battery voltage and the socket of the system being checked and watch it blink in sync with the pulses. If you use an LED, be sure to have the polarity of the LED correct. If it is wrong, you won't damage anything, but the LED won't ever turn on. In the special case of reading top controller codes on cars made through 12/93, you don't even need the LED -- just watch the top control switch on the console flash. This is possible because one side of the lamp inside the switch is wired to the diagnostic socket for the top control system.
Once you have read all of the codes, you may wish to go back and erase them. They are erased individually one at a time. To do this, read a code, wait a few seconds, and then short the diagnostic socket to ground for 6 to 8 seconds. Special: with early versions of the top controller, you first read all the codes first and then perform a read/erase.
Each system's diagnostic output signal is wired to a socket of the car's main "diagnostic connector", X11/4. An additional pair of sockets provide connections to battery voltage and chassis ground for convenience. Early cars with continuous-fuel injection have 16 sockets, while later models have 38 sockets. The sockets are numbered for easy identification. When you make connections you should know that all circuits have protected outputs and nothing can be damaged by mistakes.
The CE light is controlled by the Diagnostic Module on a '95. The socket for the DM is socket #19, socket #3 is battery voltage and socket #1 is chassis ground.
Codes are read sequentially one at a time. That is, you trigger the system you are checking to issue a code, you read the code, you trigger another code, and so on. With the key on and engine off, you trigger a code from a system by electrically shorting it's socket to ground for 2 to 4 seconds using a wire. A second or two after the wire is removed, a series of electrical pulses will occur at the socket. The number of pulses corresponds to the number of a code.
There are numerous ways to view the pulses for counting and getting codes. I use a $1.29 LED from Radio Shack (P/N 276-209) connected between battery voltage and the socket of the system being checked and watch it blink in sync with the pulses. If you use an LED, be sure to have the polarity of the LED correct. If it is wrong, you won't damage anything, but the LED won't ever turn on. In the special case of reading top controller codes on cars made through 12/93, you don't even need the LED -- just watch the top control switch on the console flash. This is possible because one side of the lamp inside the switch is wired to the diagnostic socket for the top control system.
Once you have read all of the codes, you may wish to go back and erase them. They are erased individually one at a time. To do this, read a code, wait a few seconds, and then short the diagnostic socket to ground for 6 to 8 seconds. Special: with early versions of the top controller, you first read all the codes first and then perform a read/erase.
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Joined: Nov 2006
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From: Alexandria, LA.
92 500SL
The procedure described here works for all systems with diagnostics on the R129 through model-year 1995 except for the SRS (airbag) for '94 and '95.
Each system's diagnostic output signal is wired to a socket of the car's main "diagnostic connector", X11/4. An additional pair of sockets provide connections to battery voltage and chassis ground for convenience. Early cars with continuous-fuel injection have 16 sockets, while later models have 38 sockets. The sockets are numbered for easy identification. When you make connections you should know that all circuits have protected outputs and nothing can be damaged by mistakes.
The CE light is controlled by the Diagnostic Module on a '95. The socket for the DM is socket #19, socket #3 is battery voltage and socket #1 is chassis ground.
Codes are read sequentially one at a time. That is, you trigger the system you are checking to issue a code, you read the code, you trigger another code, and so on. With the key on and engine off, you trigger a code from a system by electrically shorting it's socket to ground for 2 to 4 seconds using a wire. A second or two after the wire is removed, a series of electrical pulses will occur at the socket. The number of pulses corresponds to the number of a code.
There are numerous ways to view the pulses for counting and getting codes. I use a $1.29 LED from Radio Shack (P/N 276-209) connected between battery voltage and the socket of the system being checked and watch it blink in sync with the pulses. If you use an LED, be sure to have the polarity of the LED correct. If it is wrong, you won't damage anything, but the LED won't ever turn on. In the special case of reading top controller codes on cars made through 12/93, you don't even need the LED -- just watch the top control switch on the console flash. This is possible because one side of the lamp inside the switch is wired to the diagnostic socket for the top control system.
Once you have read all of the codes, you may wish to go back and erase them. They are erased individually one at a time. To do this, read a code, wait a few seconds, and then short the diagnostic socket to ground for 6 to 8 seconds. Special: with early versions of the top controller, you first read all the codes first and then perform a read/erase.
Each system's diagnostic output signal is wired to a socket of the car's main "diagnostic connector", X11/4. An additional pair of sockets provide connections to battery voltage and chassis ground for convenience. Early cars with continuous-fuel injection have 16 sockets, while later models have 38 sockets. The sockets are numbered for easy identification. When you make connections you should know that all circuits have protected outputs and nothing can be damaged by mistakes.
The CE light is controlled by the Diagnostic Module on a '95. The socket for the DM is socket #19, socket #3 is battery voltage and socket #1 is chassis ground.
Codes are read sequentially one at a time. That is, you trigger the system you are checking to issue a code, you read the code, you trigger another code, and so on. With the key on and engine off, you trigger a code from a system by electrically shorting it's socket to ground for 2 to 4 seconds using a wire. A second or two after the wire is removed, a series of electrical pulses will occur at the socket. The number of pulses corresponds to the number of a code.
There are numerous ways to view the pulses for counting and getting codes. I use a $1.29 LED from Radio Shack (P/N 276-209) connected between battery voltage and the socket of the system being checked and watch it blink in sync with the pulses. If you use an LED, be sure to have the polarity of the LED correct. If it is wrong, you won't damage anything, but the LED won't ever turn on. In the special case of reading top controller codes on cars made through 12/93, you don't even need the LED -- just watch the top control switch on the console flash. This is possible because one side of the lamp inside the switch is wired to the diagnostic socket for the top control system.
Once you have read all of the codes, you may wish to go back and erase them. They are erased individually one at a time. To do this, read a code, wait a few seconds, and then short the diagnostic socket to ground for 6 to 8 seconds. Special: with early versions of the top controller, you first read all the codes first and then perform a read/erase.
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From: Alexandria, LA.
92 500SL
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From: FLOMATON, ALABAMA
Mercedez 1995 SL500 r129, 1967 Camaro RS Convertible, 1971 Corvette Stingray T Top
Bob Terry: If I may ask a question? I have built the tester you described and it works as advertised for step 1. However, my question is, when I do the blink count and get 19 blinks that translates to LH-SFI, I don't know what the LH represents but, I used the code list and found that the SFI means ...... Sequential Fuel Injection. Is there a follow-on step to further diagnostis for instance, am I now supposed to move the wire that was in female diagnostic pin 17 over to female pin 19 to obtain further diagnostics?
