Faulty 'B' oil pressure sensor or switch itself, often due to internal contamination or diaphragm failure; Damaged, chafed, or corroded wiring in the sensor 'B' signal or ground circuit; Loose or corroded electrical connector at the sensor, especially on engines with high vibration or oil seepage; Low engine oil level or degraded oil that causes actual pressure fluctuations the sensor correctly reports; Restricted oil filter or pickup screen causing intermittent pressure drops that trip the rationality check; Failed oil pressure relief valve or variable oil pump solenoid affecting the pressure the sensor sees; Powertrain control module software calibration issue or internal driver fault on the sensor circuit

DTC codes / P05xx · Vehicle speed, idle control and auxiliary inputs / P055B

P055BEngine Oil Pressure Sensor/Switch B Range/Performance

Q: What does code P055B mean?

Engine Oil Pressure Sensor/Switch B Range/Performance. P055B indicates that the powertrain control module has detected an out-of-range or erratic signal from the 'B' engine oil pressure sensor or switch circuit, which is often a secondary monitoring point on vehicles with variable oil pressure control. The computer compares the sensor's voltage or pressure reading against expected values for the current engine speed and temperature, and flags the code when the signal falls outside a calibrated window or fails a rationality check.

P055B indicates that the powertrain control module has detected an out-of-range or erratic signal from the 'B' engine oil pressure sensor or switch circuit, which is often a secondary monitoring point on vehicles with variable oil pressure control. The computer compares the sensor's voltage or pressure reading against expected values for the current engine speed and temperature, and flags the code when the signal falls outside a calibrated window or fails a rationality check.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

Illumination of the oil pressure warning light or a generic check engine light, often with no other noticeable symptoms
Oil pressure gauge reading that fluctuates erratically, pegs at maximum, or drops to zero intermittently
A warning chime or message on the driver information center advising to stop the engine
Reduced engine power or limp-home mode on some vehicles that use oil pressure for variable valve timing or cylinder deactivation
Intermittent flickering of the oil pressure lamp at idle when the engine is hot
Rough running or stalling only if the faulty sensor circuit shares a reference voltage with other engine sensors

Common causes, most likely first

Faulty 'B' oil pressure sensor or switch itself, often due to internal contamination or diaphragm failure
Damaged, chafed, or corroded wiring in the sensor 'B' signal or ground circuit
Loose or corroded electrical connector at the sensor, especially on engines with high vibration or oil seepage
Low engine oil level or degraded oil that causes actual pressure fluctuations the sensor correctly reports
Restricted oil filter or pickup screen causing intermittent pressure drops that trip the rationality check
Failed oil pressure relief valve or variable oil pump solenoid affecting the pressure the sensor sees
Powertrain control module software calibration issue or internal driver fault on the sensor circuit

How to diagnose and fix it

Verify engine oil level and condition, then check for any stored freeze-frame data to see the engine speed and temperature when the code set
Inspect the 'B' oil pressure sensor connector and harness for looseness, corrosion, or oil intrusion, and repair as needed
Measure the sensor signal voltage and ground reference at the connector with a multimeter and compare to the manufacturer's specification
Test the sensor's resistance or voltage output across its operating range using a pressure gauge and scan tool live data
Check for technical service bulletins or calibration updates that address false P055B setting on the specific vehicle
Replace the 'B' oil pressure sensor or switch if electrical tests confirm it is out of specification, then clear codes and verify
If the code persists, perform an actual oil pressure test with a mechanical gauge to rule out a genuine low-pressure condition before condemning the PCM

What the 'B' sensor really monitors

Many vehicles use two oil pressure sensors: 'A' for the primary gauge or warning lamp and 'B' for a secondary function such as variable valve timing feedback or cylinder deactivation, so a P055B may not affect the dash gauge at all.
A common misdiagnosis is replacing the sensor when the real fault is a shared five-volt reference or ground circuit that also feeds the camshaft or crankshaft position sensors, causing multiple codes to set together.
On engines with variable displacement oil pumps, a sticking pump solenoid can produce pressure swings that the 'B' sensor correctly reports, so the sensor is not always the culprit.
Oil sludging or a restricted filter can cause intermittent pressure drops that only appear at certain engine speeds, setting P055B without ever illuminating the low-oil-pressure warning lamp.
Some aftermarket oil filters with poor anti-drainback valves cause pressure spikes on cold start that trip the rationality check, and the code returns even after sensor replacement until the filter is changed.

Can I keep driving with P055B?

If the oil pressure warning lamp is not illuminated and the engine sounds normal, you can drive cautiously to a repair shop, but avoid high engine speeds and heavy loads. If the red oil pressure lamp is on or the engine is making ticking or knocking noises, stop driving immediately and have the vehicle towed to prevent catastrophic engine damage.

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.