Identifying and troubleshooting engine lubrication system faults (Audi A6 C5)

After turning on the ignition, the oil pressure indicator light does not come on

The oil pressure sensor is faulty

Turn on the ignition, disconnect the wire from the oil pressure sensor and connect it to the "ground" (-). If the indicator light comes on, replace the sensor.

The oil pressure sensor is not receiving power due to oxidation of the contacts

Check the wire and contacts.

The signal lamp is faulty

Replace the light bulb.

Oil pressure warning light does not go out after engine start

Oil too hot

Ignore it if the indicator light goes out when you press the accelerator.

The indicator light does not go out when you press the accelerator pedal or remains on while driving

Oil pressure too low

Check the oil level. Top up if necessary. Check that the oil pressure complies with the vehicle's operating manual.

The electrical wire to the oil pressure regulator is shorted to the housing

Disconnect the wire from the oil pressure sensor and put it aside (do not bring it to the "ground" (-)). Turn on the ignition. If the indicator light comes on, check the wiring.

The oil pressure sensor is faulty

Replace the regulator.

Oil pressure too low across the entire engine speed range

There is too little oil in the engine

Add oil.

The mesh filter of the oil intake pipe in the pan is clogged

Remove the oil pan, clean the mesh filter, replace it if necessary.

The oil pump is faulty

Remove and inspect the pump. Replace it if necessary.

Defective crankshaft bearing shells

Remove the engine.

Too low oil pressure in the lower engine speed range

Due to contamination, the pressure reducing valve was stuck open

Remove and check the valve.

Oil pressure too high at engine speeds above 2000 rpm

The pressure reducing valve does not open due to contamination

Remove and check the valve.

[The text is based on materials from the website AUDIMANUAL.ru]