Low oil pressure can be a serious issue for any engine, leading to catastrophic damage if not addressed. This article explores a persistent low oil pressure problem on a 1.8 TFSI engine, diagnosed using Vcds 168, and documents the extensive troubleshooting process undertaken to identify the root cause. The fault code indicated by VCDS 168 points to “Oil Pressure Switch 3 (P168)”.
Troubleshooting Steps with VCDS 168
Initial measurements using VCDS 168 revealed an oil pressure of 1.1 bar at warm idle, increasing to 3.5 bar at 3000 RPM when the high-pressure valve activates. However, after 20 minutes of running, with oil temperature reaching 90 degrees Celsius, the idle pressure dropped to a concerning 0.5-0.6 bar.
To eliminate potential sensor issues, a new sensor with a lower switching limit of 0.3 bar was installed, but the problem persisted. This led to a systematic replacement of various components, guided by VCDS 168 readings:
- Oil Pressure Sensors: Both sensors (038919081K and 06K919081) were replaced.
- Oil Pressure Control Valves: Both valves (06K115243AB and 06K115243L) were replaced.
- Oil and Filter: New oil (Motorex SPX 5w30) and an OEM filter were used.
- Oil Filter Cover and Valve: The cover (06L115401J) and its valve (06L115678Q) were replaced.
- Oil Cooler Mechanical Valve: This valve was also replaced.
- Oil Pump: A new oil pump was installed.
Further investigations, aided by VCDS 168 data logging, included:
- Camshaft and Bearing Inspection: Minimal wear was observed on both components, ruling them out as the primary cause.
- Live Data Comparison: Comparing live data from the faulty car with a similar model revealed that the pressure control valve switched to high pressure more frequently in the problematic vehicle.
- Road Tests with External Gauge: Road tests with an external oil pressure gauge connected confirmed the fault occurred at 2-3 bar, although inconsistently.
- Piston Nozzle Control Valve Test: Disconnecting and connecting a different piston nozzle control valve had no effect on the fault frequency, despite lowering the oil pressure further.
Error Occurrence Pattern
VCDS 168 data revealed the error consistently occurred under specific conditions:
- Warm Engine: The oil temperature needed to be above 70 degrees Celsius for the fault to trigger.
- Constant Speed or Deceleration: The error manifested during steady driving or when the engine speed decreased after a load period.
- No Error at Idle or High Revs: Revving the engine at a standstill, whether parked or idling, did not trigger the fault.
Conclusion and Next Steps
Despite exhaustive efforts, the root cause of the low oil pressure fault remained elusive. The detailed documentation of the troubleshooting process, including the use of VCDS 168 for data logging and fault code reading, provides a valuable resource for others facing similar issues. Further diagnosis may require specialized tools or consultation with experienced technicians familiar with 1.8 TFSI engines. Future steps could involve checking oil galleries for blockages or investigating potential issues within the engine control unit (ECU) itself using VCDS 168’s advanced functionalities.
