P055C

Code

Generic P — Powertrain

Engine Oil Pressure Sensor/Switch B Low

Brand: Generic

Type: P — Powertrain

Views: UK: 29 EN: 45 RU: 27

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Page language: EN

Causes

Failed oil pressure sensor/switch (Bank B or sensor B)
Short to ground in the sensor signal wire
Open or high-resistance connector or wiring (poor contact, corrosion)
Low engine oil level or severely low oil pressure (mechanical)
No reference power or poor ground to the sensor
PCM/ECM internal fault (rare)

Symptoms

Check Engine Light (MIL) illuminated
Oil pressure warning or lamp may illuminate
Possible engine limp mode or reduced protection if PCM limits performance
Erratic or low oil pressure readings in scan tool data for sensor B
Possible abnormal engine noise if actual oil pressure is low

What to check

Read freeze frame and pending/confirmed status with a scan tool; record live data for oil pressure sensors
Visually inspect sensor B connector and wiring for corrosion, damage, pin push-out or contamination
Check engine oil level and condition; correct low oil before electrical diagnosis
Backprobe sensor connector to measure signal voltage, reference voltage and ground
Check for shorts to ground or opens using a multimeter (continuity and resistance checks)
Compare sensor B live data to sensor A (if present) and to mechanical oil pressure gauge

Signal parameters

Typical sensor signal: 0.5–4.5 V (varies by manufacturer). Low code usually indicates signal < ~0.3–0.5 V
Reference supply commonly 5 V (check vehicle data)
Sensor ground should be near 0 V; measure voltage drop across ground for integrity
Engine off / key on idle sensor output may show specific voltage—consult vehicle service data for exact thresholds

Diagnostic algorithm

Retrieve codes, freeze frame and live data; note whether code is current/persistent or intermittent.
Check engine oil level and top up if low. If oil was very low, clear codes and retest before electrical work.
Visually inspect the sensor B connector, wiring harness and nearby components for damage or contamination.
With ignition ON (engine off), backprobe the sensor connector: verify reference voltage (typically ~5 V), signal voltage (low per code), and good ground.
If reference voltage is missing, trace power supply/fuse/relay and repair open circuit. If signal is short to ground, isolate wiring and repair short.
Wiggle test wiring while monitoring signal voltage to reproduce intermittent faults; repair chafing or broken conductors.
If wiring and supply/ground OK but signal stays low, swap with a known-good identical sensor (if applicable) or measure sensor resistance per service manual; replace sensor if out of spec.
If replaced sensor and wiring are good but fault remains, inspect PCM connector and grounds. Consider PCM test or replacement only after eliminating wiring and sensor faults.
If there is concern about actual oil pressure, attach a mechanical oil pressure gauge to verify true pressure before engine damage occurs.
After repairs, clear codes and perform drive cycle/functional test to confirm the fault does not return.

Likely causes

Corroded/loose connector at the oil pressure sensor
Sensor B internal failure (stuck low or shorted)
Signal wire damaged and shorted to chassis ground
Missing/weak sensor reference voltage (blown fuse, open supply)
Actual oil pressure extremely low due to oil starvation or failed oil pump

Fault status

⚠️ Status

Powertrain Control Module reports Engine Oil Pressure Sensor/Switch B signal at abnormally low voltage (circuit indicates low input or short to ground).

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours