Differential pressure sensor G450 to be calibrated/adjusted (for TDI/DPF) (Solution)

The differential pressure sensor in current TDI models measures the pressure drop of the exhaust gases across the particulate filter. Using these measurements and other parameters, the engine control unit calculates the DPF's loading condition and ash mass.

The sensor measures relatively small pressure differences. Over time, its readings for "no pressure difference" or "small pressure difference" can shift, so that the engine control unit continuously adjusts the baseline values in the background.
For example, if the ignition is turned on without the engine running, no differential pressure can be expected, and the control unit can take into account the measured values supplied by the sensor to adjust the calibration values.

The differential pressure sensor either gradually fails, or its quiescent values become so nonsensical that the adjustment in the control unit reaches its limits (apart from the fact that the values are then no longer accurate), or it suddenly fails due to a failure of the sensor within the component.

The differential pressure sensor then needs to be replaced. Then, and only then, is adjusting the learning values sensible and necessary: This ensures that the measurement values of the new sensor are correctly interpreted by the engine control unit from the start, and do not have to go through a lengthy learning process.

Resetting learning values or Adjusting values can be done with VCDS as follows:

- Ignition ON, Engine OFF.
- VCDS -> 01 - Engine -> Coding II or Login / Security Access.
Enter the login code from the VCDS tooltip (Adjusting Exhaust Gas Sensor 1 (G450)).
- Ignition OFF

With newer engine control units, the adjustment of the differential pressure sensor is often carried out via the "Adjustment" function.

There are newer TDI systems with two differential pressure sensors:
- G450 is the exhaust gas pressure sensor
- G505 is the DPF differential pressure sensor (differential pressure between the inlet and outlet of the filter element)

To reset the learning values, please refer to the corresponding option in VCDS.