DR_RET_SHORT_GND; Retarder Modulation Solenoid Valve; Short circuit to ground
Switch off ignition; Disconnect electronics incl. transmission cables; Connect transmission checking cables; Measure resistance of the proportional valve against ground/housing (pin 8 against ground (KL31)/housing) Nominal value: > 10 Mohm; Check cable TCU -> transmission; If you find deviations from nominal value, check wiring and component;
What you'll see
No driver-visible symptom recorded.
System reaction
Activate "Central Solenoid Disconnection Unit";
Diagnostic depth
The total current of all current regulators is higher than theoretically necessary Readback voltage is significantly lower than VPS (Kl30) Control frequency is higher than maximum permitted control frequency Current regulator indicates fault; AIM switched on or off
Transmission shifts to neutral (gear loss) Retarder is no longer available;