What does it mean?
P1609 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Internal Control Module Engine Oil Temperature Performance .
Symptoms
- MIL (check engine lamp) on
- Oil temperature gauge reading wrong, stuck or pegged where the vehicle has one
- Service interval or oil life calculation clearly wrong, service message far too early or too late
- Cooling fans running longer than usual or cutting in at odd moments
- Slightly altered shift or fan behaviour, otherwise little change in drivability
- No temperature reading at all in the scan tool data list
Likely causes
- Engine oil temperature sensor drifting out of range or reading intermittently
- Corroded connector or high resistance in the oil temperature circuit, open circuit or short to ground
- Very low engine oil level so the sensor is not properly immersed
- Oil temperature and coolant temperature values that do not correlate, meaning one of the two sensors is wrong
- Damaged harness near the sump or heat-damaged insulation next to the exhaust
- Module software not matched to the sensor calibration after an update
- Internal processing fault in the module for that temperature channel
How to fix it
- Compare oil, coolant and intake air temperature in live data after the vehicle has stood overnight; all three should agree within a few degrees
- Check the engine oil level and condition before any electrical testing
- Back-probe the oil temperature sensor circuit and measure the reference voltage and signal voltage with the ignition on
- Measure sensor resistance at a known temperature and compare with the specification curve
- Check the sensor ground and look for corrosion or heat damage at the connector near the sump
- Replace the sensor if its curve is out, then re-evaluate whether the internal code returns
- Update the module software; replace and program the module only if the fault stays with a verified good sensor circuit