| Mercedes OBD1 Fault Codes 1988-1995 |
Got some files you'd like to share with others? I'd gladly put them on this page are credit you. email mercedescodereader@gmail.com Thanks, Rick
| 124 Wire and Plug locations |
Below links courtesy W124performance
| 38 Socket location and details - www.W124performance.com |
| Supplemental OBD1 Code info. for the 119 engine - www.W124performance.com |
| 88-95 w124 w129 Code Reading 38 Socket - Nice article! |
Mercedes Benz C-Class cars Lots of information here
How to Search PDF 2:52
How to clear codes 4:55
How to clear codes 4:55
Peter Davidson in Brandon Florida made a fantastic video on code reading. It's the same procedure for all OBD1 cars with 8,16 or 38 socket cars. Please subscribe to his Youtube channel.
My #1 Customer Question
Why does the LED light immediately turn on when I plug in the yellow wire? The LED immediately turning “ON or Dim” means the system/circuit you're testing has a closed fault due to a stuck relay, solenoid, corrosion on contacts or even spider webs allowing phantom voltage to pass. The circuit being closed prevents the code reader from receiving pulse voltage from the car’s diagnostic module. I'd start unplugging relays and whatever else you can jiggle around on that system. Then onto replacing parts. Mercedes wasn’t too smart designing the OBD1 code system like Christmas tree lights....if one part is fused you can't read any codes on that entire system.
Why won’t some codes clear?
Codes that won’t clear or show up again after clearing are considered "hard" codes and will require replacement parts. These cars are almost 30 years old so don’t expect code reading to be exact. Codes you read and clear today may appear again along with other new codes. Dirt, corrosion, cracked wiring harness, all affect the diagnostic module. Fun but frustrating.
Download my PDF code file at www.mercedescodereader.com/files.html It contains ALL codes Mercedes published for 88-95 cars.
When reading codes, one blink or no blink indicates there is no stored code on that system.
Want to check if your code reader is functioning properly?
Round socket with 9 holes?
None of my code readers will work. Those cars are not OBD1 and do NOT have a diagnostic module. The 9 pin is read with an ohm meter to determine on/off values. I don't have any experience or details on the 9 pin. I see a video on youtube that may help.
https://www.youtube.com/watch?v=5syKYwfEyCo&list=PLg-Bx-y-F2JDJa7AaQWXykPryK8C5yuJS
Before purchase Look at the code file and see if the systems you need to diagnose are listed. If your car has an OBD1 connection port buy the one that will plugs into your car.
Why does the LED light immediately turn on when I plug in the yellow wire? The LED immediately turning “ON or Dim” means the system/circuit you're testing has a closed fault due to a stuck relay, solenoid, corrosion on contacts or even spider webs allowing phantom voltage to pass. The circuit being closed prevents the code reader from receiving pulse voltage from the car’s diagnostic module. I'd start unplugging relays and whatever else you can jiggle around on that system. Then onto replacing parts. Mercedes wasn’t too smart designing the OBD1 code system like Christmas tree lights....if one part is fused you can't read any codes on that entire system.
Why won’t some codes clear?
Codes that won’t clear or show up again after clearing are considered "hard" codes and will require replacement parts. These cars are almost 30 years old so don’t expect code reading to be exact. Codes you read and clear today may appear again along with other new codes. Dirt, corrosion, cracked wiring harness, all affect the diagnostic module. Fun but frustrating.
Download my PDF code file at www.mercedescodereader.com/files.html It contains ALL codes Mercedes published for 88-95 cars.
When reading codes, one blink or no blink indicates there is no stored code on that system.
Want to check if your code reader is functioning properly?
- Touch the Red to battery positive and the Yellow to battery negative and the LED should immediately turn itself on.
- Touch the Red to battery positive and Black to battery negative and PUSH the button and the LED should turn on.
Round socket with 9 holes?
None of my code readers will work. Those cars are not OBD1 and do NOT have a diagnostic module. The 9 pin is read with an ohm meter to determine on/off values. I don't have any experience or details on the 9 pin. I see a video on youtube that may help.
https://www.youtube.com/watch?v=5syKYwfEyCo&list=PLg-Bx-y-F2JDJa7AaQWXykPryK8C5yuJS
Before purchase Look at the code file and see if the systems you need to diagnose are listed. If your car has an OBD1 connection port buy the one that will plugs into your car.
Got a car with the Push button and LED on the diagnostic socket?
Kent at Mercedes Source is super sharp with Mercedes. See his video above and check out his website. https://mercedessource.com/
If your car has a button and LED test port you can read and clear your codes without an external code reader. If not, you need to buy my code reader which does the exact same thing as the little button does. Except my code reader plugs into each individual socket and gives you flash codes for all your systems.
If your car has a button and LED test port you can read and clear your codes without an external code reader. If not, you need to buy my code reader which does the exact same thing as the little button does. Except my code reader plugs into each individual socket and gives you flash codes for all your systems.
Make your own code reader
Build your own OBD1 Code Reader for less than $5. Diagram shows an LED but you can use any 12 volt bulb. The LED makes it easier to count the number of light flashes being quick on and off. Only difference in code readers is the size of the wire ends. Its banana plug for the 8 and 16 socket cars. For cars with the round 38 socket the ends are 1mm or 18 gauge. Also download my OBD1 Code Listing PDF on this site.
