Documentary: DPF (Diesel Particulate Filter) Problems in 2.5 TDI and 1.9 PD Engines (Solution)

Only automatic vehicles with a 2.5L TDI engine and a 1.9L PD engine are affected.

The transmission control unit has a fault code indicating "gear monitoring, incorrect gear ratio," and the engine control unit has a fault code indicating "coolant temperature sensor - G62, intermittent." The automatic transmission may already be experiencing slippage issues in the 4th or 5th gear.

The coolant temperature sensor occasionally detects a temperature that is much too low (e.g., -4°C instead of 60°C). As a result, the engine control unit calculates a much too low (incorrect) engine torque, which is transmitted via the CAN bus to the transmission control unit for ATF pressure calculation (e.g., calculated: 20 Nm, actual: 190 Nm). The clutches are then held with insufficient pressure, causing them to slip. This primarily damages clutch E, which is used in the 4th and 5th gears. The component responsible for power transmission.
The coolant temperature sensor is only recognized as faulty if the engine control unit detects a break or short circuit to the positive terminal. After the engine is restarted, this error message becomes a sporadic error, and the damage to the transmission can begin again.


Procedure:

Read the error codes from the engine and transmission control unit.

If the described errors are stored in the engine and transmission control unit, the coolant temperature sensor should be replaced, and the automatic transmission should be checked for proper clutch engagement, especially in 4th and 5th gear. To do this, disconnect the transmission control unit from the vehicle's wiring harness and perform a static brake speed test in drive (D) for a maximum of 5 seconds (the transmission will be in emergency mode in 4th gear). If the engine speed exceeds 2800 RPM, this indicates a slipping clutch.

Sure, here's the translation:

"Note:"
When assessing the condition of the ATF (Automatic Transmission Fluid), it should be noted that in diesel vehicles, the high stress on the torque converter clutch in properly functioning transmissions can cause the ATF to darken significantly after mileage exceeding 20,000 km. The ATF can only be definitively assessed based on its smell, which can indicate whether it has been "burned" or "not burned" when compared to new ATF.

After replacing the coolant temperature sensor in measurement block 009 of the transmission control unit, the engine torque during driving must be checked for plausibility to eliminate any potential additional sources of error. The actual torque should be approximately equal to the maximum torque documented in the technical specifications (within +/- 5%) when operating at full load.

Pay attention to tuning instructions, as this could also damage the "E" clutch.

Sure, here's the translation:

"Note:"
The coolant temperature displayed on the instrument cluster may not be identical to the temperature read by the engine control unit, as the coolant temperature sensor operates with two independent, temperature-dependent resistors.