Oil Pressure Sender: Testing and Inspection
Oil Pressure and Oil Pressure Switch, Checking
Special tools, testers and auxiliary items required
• Oil pressure gauge (V.A.G 1342)
• Voltage tester (V.A.G 1527B)
• Connector test kit (V.A.G 1594C) or (V.A.G 1594A)
Function of the Dynamic Oil Pressure Warning System
When not under pressure, the oil pressure switch is open and will close when the operating pressure is attained.
The oil pressure warning is activated approximately 10 seconds after switching on the ignition ("terminal 15 on").
Switch-on delay of oil pressure warning: approximately 3 seconds
Switch-off delay of the oil pressure warning: approximately 5 seconds
Check the Warning Light
After switching on the ignition without starting the engine, the oil pressure warning lamp in the instrument cluster insert must illuminate for approximately 3 seconds and then extinguish. The check will be interrupted when the engine is running.
Criteria for Warning
The optical oil pressure warning switches on (oil pressure warning lamp lights up continuously) and the buzzer sounds three times for the acoustical warning under one of the following conditions:
• "Ignition on", engine stationary, oil pressure switch closed
• Engine speed above 1500 RPM, oil pressure switch open
- When the engine speed is greater than 5,000 RPM, the oil pressure warning is not cancelled; even if the oil pressure switch is closed. Oil pressure warning cancelled below 5000 RPM
- If the oil pressure switch is open for 0.5 to 3 seconds when the engine speed is greater than 1500 RPM, it will be stored in the combi-processor in the instrument panel insert. If this condition occurs three times when the engine is running, the oil pressure warning will be activated and will not be cancelled even below 1500 RPM. The oil pressure warning is cancelled, when the oil pressure switch is closed for longer than 5 seconds at an RPM above 1,500 or when the "ignition is off".
Test Conditions
• Engine oil level OK, checking => [ Oil Dipstick Markings ] Component Tests and General Diagnostics.
• Oil pressure warning lamp (K3) must light up for approximately 3 seconds when ignition is switched on
• Coolant temperature at least 80° C (radiator fan must start up once)
Test Sequence
- Remove oil pressure switch (F1) and screw into oil pressure gauge.
- Thread oil pressure gauge into oil filter bracket in place of oil pressure switch.
- Connect brown wire of tester to ground (GND) (-).
- Connect voltage tester (V.A.G 1527B) using assist cables from (V.A.G 1594C) to battery (+) and oil pressure switch.
LED must not light up.
- When the LED illuminates, replace the oil pressure switch (F1).
If the LED does not light up:
- Start engine and slowly increase engine speed.
The LED must illuminate at 0.55 to 0.85 bar positive pressure, otherwise replace the oil pressure switch.
- Increase engine speed further.
At 2000 RPM and an oil temperature of 80° C, oil pressure must be at least 2.0 bar.
At higher engine speeds oil pressure must not exceed 7.0 bar
If the specified values are not reached:
- Check screen in intake line for soiling => [ (Item 11) Suction line ] Oil Pan and Pump Assembly Overview.
• Also, mechanical damage e.g. bearing damage can also be the cause of too low oil pressure.
If no malfunction can be found:
- Replace oil pump.
If the specification is exceeded:
- Check oil channels.
- If necessary, replace oil filter bracket with pressure relief valve => [ (Item 4) Oil filter bracket ] Service and Repair.