TDI Engine Problems: Low Power & Error Code 00553 (Solution)

V6 TDI
a) Gradually decreasing engine power.
b) Sudden power loss in rainy conditions; possibly error code 00553 (mass airflow sensor, implausible signal) stored in the engine control unit.

Cause:
a) Oil mist gradually accumulates on the sensor membrane of the mass airflow sensor. The mass airflow sensor signal becomes increasingly distorted, leading to a noticeable loss of power. If the "warm-up phase" of the mass airflow sensor, which lasts for 4 minutes after the engine is turned off, is still active, the oil mist will additionally become "stuck" on the membrane.
Due to the gradual change, errors are usually not introduced.

b) In heavy rain and at very high speeds, water splashed up by vehicles ahead can be sucked into the engine. In extreme cases, the air filter element becomes completely saturated, and water reaches the mass airflow sensor. This sudden change in signal causes a loss of power; error code 00553 may be stored, and the engine control unit enters emergency mode.


Procedure:
a) Check the mass airflow sensor. Verify the target and actual values of the air mass being drawn in under load using measurement block 10. Replace the mass airflow sensor if the target values are not met.
can be achieved.

Using a voltmeter or test lamp, check at pin 2 of the mass airflow sensor to see if there is still voltage present after the engine has been turned off by switching off the ignition. If voltage is still present, as a preventative measure against further contamination of the mass airflow sensor, the "warm-up phase" must be interrupted, and the power supply to the mass airflow sensor should be connected directly to terminal 15 (ignition).

Procedure for A4/A6:
1. Disconnect the wire from pin 2 of the mass airflow sensor and insulate the exposed end of the wire. The connector is numbered.

Run a new cable with an insulating tube (cross-section 1 sq mm) and a 2.8 mm gold contact, using single-strand wire sealing, from pin 2 of the mass airflow sensor to the output of fuse 31 in the central electrical unit. (Fuse 31 = reversing lights = terminal 15).
Route the cable along the engine wiring harness.
existing rubber grommets into the water tank and further into the...
E-Box.

3. Turn on the ignition. There should be approximately battery voltage at pin 2 of the mass airflow sensor. Start the engine. After turning off the engine by switching off the ignition, there should be no voltage at pin 2 anymore. Supplying direct voltage does not affect the driving behavior; it is purely a preventative measure against recontamination.

Procedure for A8:
Connect a wire from the terminal 15 power supply cable to the engine control unit in parallel, and run it to an available fuse slot in the central electrical system, securing it with a 5-amp fuse.

Disconnect the wire from pin 2 of the mass airflow sensor, cut the wire, and insulate the cable. The connector is numbered.

Run a new cable with an insulating tube (cross-section 1 sq mm) and a 2.8 mm gold contact, along with single-wire sealing, from pin 2 of the mass airflow sensor to the output of the free fuse in the central electrical system.
Route the cable along the engine wiring harness through existing rubber grommets into the water tank and then to the electrical box.

4. Turn on the ignition. There should be approximately battery voltage at pin 2 of the mass airflow sensor. Start the engine. After turning off the engine by switching off the ignition, there should no longer be any voltage at pin 2. Supplying direct voltage does not affect the driving behavior; it is purely a preventative measure against recontamination.

b) Check the air filter element for water ingress. If water has been drawn in, replace the air filter element. Bosch mass airflow sensors (with a black plastic housing) must be replaced with a new Bosch part after contact with water and if a negative result is obtained during testing in measurement block 10. Hitachi mass airflow sensors (with an aluminum housing) typically do not need to be replaced after contact with water, provided that a test drive can be completed without any issues.
It is not possible to interchange air mass flow sensor units between different models.

As a preventative measure and to avoid recurring issues (water intake), the following parts (Nordland version) can be installed:

A4:
Air filter lower section with snow deflector, part number 4B0 133 837 F.

A6:
Air filter lower section with snow deflector, part number 4B0 133 837 F. Air intake duct with coarse mesh grille, part number 4B0 129 617 F.

A8:
Air filter lower section with snow deflector, part number 4B0 133 837 N.
Below the air filter, there is a circular...
Body opening to the wheel well through which the fuel lines are routed. To prevent spray water from being drawn in through this body opening and into the auxiliary air intake of the air filter, this opening should be sealed with suitable sealing foam.