What this code means
P055D may indicate that the PCM is seeing a high-voltage signal from the rocker arm oil pressure sensor B circuit.
What the vehicle may do
- The vehicle may turn on a warning light.
- The engine may seem to run normally in some cases.
- The PCM can change how it manages the rocker arm oil pressure control strategy.
Possible fault areas
- Possible sensor signal circuit issue.
- Possible sensor ground-side issue.
- Possible rocker arm oil pressure sensor issue.
- Possible connector or wiring issue.
- Possible PCM-related issue after other checks are normal.
Diagnostic path
Opening and code meaning
On this 2016 to 2024 Honda Civic with the 1.5 turbo engine, P055D points to the rocker arm oil pressure sensor B signal being higher than the PCM expects. In plain language, the computer is seeing a high-voltage signal on that oil pressure sensor circuit. The car may run normally, or it can set a warning light and affect how the PCM manages the rocker arm oil pressure control strategy. Broadly, the possible fault areas may include the sensor signal circuit, the sensor ground side, the rocker arm oil pressure sensor itself, related connector or wiring issues, and only after the other checks pass, the PCM. Start with the basic system checks, and if other codes are present, check what they mean first so you are not chasing this one out of context.
Confirm the failure first
Begin by confirming whether the fault is actually present. Turn the vehicle to the ON mode, then look at the HDS value for rocker arm oil pressure sensor B voltage. If that value is more than 4.79 V, the failure is duplicated. That gives you a real high-voltage condition to diagnose instead of just working from stored memory.
Check how the circuit responds with the sensor disconnected
Next, move into the rocker arm oil pressure sensor inspection. There is no direct method here to test the component by itself, so the diagnosis is done by checking the related parts of the circuit. Disconnect the rocker arm oil pressure sensor 3P connector. Then jump terminals No. 1 and No. 2 of that connector with a jumper wire. Turn the vehicle to the ON mode and confirm the same HDS voltage value again. In this check, normal is less than 4.79 V. If the circuit responds normally with the jumper in place, the problem points back to the rocker arm oil pressure sensor. If it does not respond normally, keep going because the problem is in other related components or wiring.
Protect the PCM before connector work
Before disconnecting the PCM connector, use the HDS to jump the SCS line and wait more than 1 minute. Do not skip that pause. After that, disconnect the rocker arm oil pressure sensor 3P connector, then disconnect PCM connector E, the 80P connector.
Check the P-OIL and SG2 wiring
Now perform the open-wire inspection for the P-OIL and SG2 circuits according to the connector table. For the SG2 open-wire inspection with the circuit OFF, normal is less than 1 Ω. For the P-OIL open-wire inspection with the circuit OFF, normal is also less than 1 Ω. If either check is abnormal, the problem is in the circuit. If those wiring checks are normal, the diagnostic path moves on to the remaining control side.
PCM conclusion and final takeaway
If the sensor-side inspection and the P-OIL and SG2 circuit checks all show normal results, the remaining cause is the PCM. At that point, do not guess or jump ahead; the logic of this code is to prove the high sensor voltage, prove whether the circuit can be pulled below the threshold, prove the related wiring is intact, and only then call the PCM. The takeaway: P055D is a high-voltage sensor-circuit diagnosis, so confirm the voltage first, use the jumper test to separate the sensor from the circuit, then finish with the open-wire checks before making a PCM call. For more diagnostic training, visit stepdiagnostics.com.
Final check
P055D is often approached as a high-voltage sensor-circuit fault: confirm the signal, separate the sensor from the circuit, check the related wiring, and only then consider the remaining control side.
For more guided automotive diagnostics, visit STEP Diagnostics.
