PeachParts Mercedes-Benz Forum - View Single Post

JimF · #12 01-28-2005, 02:32 AM

. . 'bad', you will get codes in the Diag (pin 19), EA w/ ASR (pin 7) and ABS w/ASR (pin 6) Modules. My case was typical for what happens in a V8, "S" class car. Check out Menu #24 to see what codes were set.

The EA module as well as the DM have multiple levels of fault storage; Active, Registered and Stored. Here's what they mean.

Active Faults - These faults are detected while the car is running at idle or speed. They represent a component that maybe or is currently failing. These codes cannot be erased. They are only meaningful with the ignition on and the engine running so DTCs found in this system with the "key-on-engine-off" usually have no meaning. Sometimes it shows a components not present on the car as failing so these codes do more to confuse than to serve as a diagnostic tool. But if the code persists, and the CEL lights, then it indicates a bad component but not necessarily the DTC that stated!!! Thus the confustion.

Registered Faults - These faults are recorded in the temporary memory of the of the car's ECUs. This temporary memory records the the fault indicating that it has occurred and is continuing to occur but it hasn't exceed the preset number of times to make it a Stored fault. When that certain number of failures has occurred, the fault is now moved to permanent (Stored) memory and the CEL lights. Some ECUs that have internal fault registers, the CEL may stay on after the Stored or Permanent fault has been erased if another occurrence of the fault has happened since the 'permanent' fault was stored. To extinguish the CEL, you should always erase both Stored and Registered faults.

Stored Faults - These DTCs are sometimes called 'permanent' codes. These faults are recorded in the permanent memory of the car's ECU and are the main cause of CEL light. They have been generated because the fault exceeded the preset number of times set up for for that function. These DTCs can (and should) be erased.