Engine

P01BC — Engine Oil Temperature Sensor B Circuit High

Severity: medium Drive with care, to a shop

What P01BC means

The engine control module detected a voltage in the oil temperature sensor B circuit that is higher than expected. The sensor is a thermistor, so its resistance and the signal voltage change with oil temperature. A high reading usually points to an open circuit, poor connection or a short to voltage.

Symptoms

  • Check Engine light is on
  • Oil temperature reading is wrong or missing
  • Erratic behavior of functions that depend on oil temperature, if equipped
  • Engine may switch to a default control strategy

Possible causes

  1. Failed oil temperature sensor B
  2. Open circuit in the signal or ground wire
  3. Signal wire shorted to voltage
  4. Corroded or loose sensor connector
  5. Damaged harness insulation near hot engine parts
  6. Faulty engine control module (rare)

How to diagnose

  1. Scan for all codes and freeze frame data and look for other temperature sensor codes
  2. Read oil temperature on a scan tool: a cold engine should show roughly ambient temperature, not a value stuck at the minimum or maximum
  3. Inspect the sensor, connector and harness for oil contamination, chafing, heat damage and corrosion
  4. Unplug the connector and check for reference voltage (typically about 5 V) and a good ground using the wiring diagram
  5. Measure sensor resistance and compare it with the manufacturer's chart at a known temperature
  6. Test the wires back to the module for opens and shorts to voltage
  7. If wiring and sensor are good, check the module and look for a software update

Common fixes

  • Replace oil temperature sensor B
  • Repair the damaged wire or replace the connector
  • Clean the terminals and fix the cause of corrosion
  • Reflash or repair/replace the control module (last resort)

Questions and answers

What does P01BC mean?

The engine control module sees too high a voltage from oil temperature sensor B. The most common causes are a bad sensor, a broken wire or a poor connector contact.

Can I drive with P01BC?

For a short time, yes, but get it fixed soon. The module doesn't know the real oil temperature, which can affect engine control.

How can I quickly test the sensor?

Unplug the connector and inspect the terminals, then measure the sensor resistance and compare it with the spec. Also check what the scan tool shows for oil temperature on a cold engine.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.