What does it mean?
This code covers an engine oil temperature sensor B signal that is present but unstable, dropping out or jumping between samples. Oil in a sump has enormous thermal inertia, so the temperature can only change gradually; a reading that moves tens of degrees in a fraction of a second cannot be real and is flagged as an intermittent or erratic circuit.
The sensor is mounted on the engine where heat cycling, oil mist and vibration attack the connector and the harness, which is why terminal fretting and cracked insulation dominate the cause list. Because the module briefly acts on each bad sample, functions like variable valve timing can behave oddly for a moment before the value is rejected. Faults like this rarely reproduce at idle, so wiggle testing while graphing live data is the practical approach.
Symptoms
- MIL (check engine lamp) that comes and goes without any repair
- Oil temperature value on a scan tool that spikes or drops momentarily
- Occasional brief roughness or a change in engine note as valve timing reacts to a bad sample
- Fault appearing after driving over rough surfaces or once the engine is fully hot
- Oil temperature warning appearing briefly and then clearing
- Nothing reproducible with the engine idling in the workshop
Likely causes
- Loose or fretted terminals in the oil temperature sensor B connector
- Oil and dirt inside the connector degrading the contact surfaces
- Chafed signal wire that grounds only when the engine rocks on its mounts
- Heat-embrittled insulation cracking where the harness passes near the exhaust
- Intermittent internal open in the thermistor, often appearing only when hot
- Corroded or loose engine ground point opening under vibration
- Loose connector at the engine control module
How to fix it
- Check the freeze frame for the temperature, load and speed present when the code set
- Graph the oil temperature B signal while wiggling the connector and moving the harness section by section with the engine running
- Check terminal tension with a matching pin and inspect the contact faces for oil, dirt and fretting corrosion
- Follow the harness along the block looking for rub points at brackets, hoses and heat shields
- Voltage drop test the ground circuit with the engine hot and vibrating rather than at rest
- Repair or replace the affected terminals, clean and secure the connector, protect the loom from heat, then road test to confirm the trace stays smooth
- Replace oil temperature sensor B if the signal continues to drop out with a proven harness, especially when the fault only occurs at operating temperature