Faulty oil pressure sensor 'B' (internal failure or contaminated sensing element); Low engine oil level or degraded oil; Wiring damage (open, short, or chafed harness) between sensor and ECM; Corroded or loose electrical connector at the sensor; Clogged oil passage or restricted oil filter; Oil pump wear or failure (less common); ECM software or internal fault (rare)

DTC codes / P05xx · Vehicle speed, idle control and auxiliary inputs / P055C

P055CEngine Oil Pressure Sensor/Switch B Low

Q: What does code P055C mean?

Engine Oil Pressure Sensor/Switch B Low. P055C indicates that the engine control module has detected a low signal from the engine oil pressure sensor or switch designated as 'B', which is typically the second sensor in a multi-sensor system. The computer compares the reported oil pressure against expected values for the current engine speed and temperature, and it sets this code when the signal falls below the low threshold.

P055C indicates that the engine control module has detected a low signal from the engine oil pressure sensor or switch designated as 'B', which is typically the second sensor in a multi-sensor system. The computer compares the reported oil pressure against expected values for the current engine speed and temperature, and it sets this code when the signal falls below the low threshold.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

Oil pressure warning light or message on the dashboard
Gauge showing low or zero oil pressure, sometimes fluctuating
Audible chime or buzzer warning
Engine may enter reduced power or limp mode
Often no symptoms besides the warning light
In severe cases, engine knocking or ticking if actual oil pressure is low

Common causes, most likely first

Faulty oil pressure sensor 'B' (internal failure or contaminated sensing element)
Low engine oil level or degraded oil
Wiring damage (open, short, or chafed harness) between sensor and ECM
Corroded or loose electrical connector at the sensor
Clogged oil passage or restricted oil filter
Oil pump wear or failure (less common)
ECM software or internal fault (rare)

How to diagnose and fix it

Check engine oil level and condition; top up or change oil if needed
Inspect sensor 'B' connector and wiring for damage or corrosion; clean and secure
Use a scan tool to view live oil pressure data and compare with a mechanical gauge
Test the sensor 'B' signal circuit for continuity and short to ground
Replace the oil pressure sensor 'B' if faulty
Check oil pressure with a mechanical gauge to verify actual pressure; if low, inspect oil pump and passages
Clear codes and verify repair with a test drive

What most technicians overlook with P055C

A low oil pressure reading from sensor 'B' often reflects a failing sensor rather than actual low oil pressure, so always verify with a mechanical gauge before condemning the engine.
On vehicles with two oil pressure sensors, sensor 'B' may monitor a different oil gallery or provide a redundant signal, and its failure can set this code without any drivability symptoms.
Wiring harness chafing near hot exhaust components or sharp edges is a common cause that is frequently missed during visual inspection.
After an oil change, air pockets or debris can temporarily disrupt sensor 'B' readings and set a false code; clearing it and rechecking after a short drive may resolve it.
The ECM may use sensor 'B' for variable valve timing or cylinder deactivation logic, so a low signal can cause subtle performance issues beyond a warning light.

Can I keep driving with P055C?

If the oil pressure warning light is on and accompanied by engine noise, stop driving immediately to avoid catastrophic damage. If only the code is stored with no noise or performance change, you may drive cautiously to a repair shop, but avoid high speeds and heavy loads.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.