Table of contents: Brake fluid level indicator light ↓ Oil pressure switch ↓ Troubleshooting ↓ Replacing the oil pressure sensor ↓
Brake fluid level indicator light
The oil pressure in the Audi A4 engine is monitored by an oil pressure sensor in conjunction with an electronic logic unit in the instrument cluster. The signal is therefore no longer given based on the oil pressure alone, but in conjunction with the coolant temperature and engine speed. Criteria for switching on the warning light:
- The engine is not running, the oil pressure sensor is closed.
- The coolant temperature is above 60°C, the engine speed is above 1500 rpm and the oil pressure sensor is open.
- Coolant temperature is below 60°C, engine speed is above 300 rpm and oil pressure sensor is open.
- At engine speeds above 5000 rpm, the activated oil pressure signal does not turn off (regardless of the position of the oil pressure switch).
- If the oil pressure sensor remains open for more than 0.5 s when the engine is running at speeds above 1500/min, this information is stored in the computer. If this condition occurs three times in a row, the warning signal is activated and does not turn off, even if the speed drops. The countdown starts again from the next time the ignition is turned on.
Oil pressure switch
Four- and six-cylinder engines have different oil pressure sensors, the insulated parts of which are of different colors for distinction:
- Black colour for oil pressure switch from 1.4 bar in four-cylinder engines.
- White colour for oil pressure switch from 1.8 bar in six-cylinder engines.
Troubleshooting
If the signal light (sometimes with a sound signal) lights up when the engine is running, you must stop immediately!
Turn off the engine immediately, check the oil level. If everything is OK, then:
- Have your vehicle towed to prevent more serious damage due to lack of lubrication.
- As a next step, check the oil pressure.
- If the oil pressure is OK, then you can change the oil pressure sensor (in the workshop).
- If, despite this, the lamp does not go out, then the reason is in the device.
Replacing the oil pressure sensor
The wires to the oil pressure sensor and to the oil temperature sensor in a six-cylinder engine are connected at this plug connector (arrow) on the rear of the left cylinder head.
On the left, next to the crankshaft belt pulley in a six-cylinder engine, there is an oil temperature indicator sensor (1) and an oil pressure sensor (2).
1. Buy the correct oil pressure sensor with black or white insulation and a new sealing ring for it.
2. Tighten the oil pressure sensor to 25 Nm only.
[The text is based on materials from the website AudiManual.ru]