P055D means the powertrain control module (PCM) saw the signal from engine oil pressure sensor B stuck at the high end of its range. It sits in a small family of codes for a second oil pressure sensor: P055B for range or performance, P055C for a low signal, P055D for a high signal, and P055E for an intermittent one. The word "B" is what makes this code specific. Sensor A is the ordinary oil pressure sensor or switch that drives the warning light and the gauge. Sensor B, on the vehicles that set this code, monitors oil pressure in a control circuit downstream of a solenoid, and its job is to confirm that a valve-timing mechanism did what the computer asked.
Severity: low to moderate. Can you keep driving? Yes. The engine's main oil pressure is not in question; a different sensor watches that. What the PCM loses is confirmation that its variable valve mechanism is switching, so it typically disables the high-lift or high-rpm mode and runs the engine conservatively. Expect a check engine light, a slight loss of top-end power and no drivability drama. A flashing light or a red oil pressure lamp is a different problem; see why a flashing light means stop.
Which vehicles set P055D
The generic definition applies to any engine with a second oil pressure sensor, but in practice the population is dominated by Honda's turbocharged four-cylinders: the 1.5 L and 2.0 L in the 2018 and newer Accord, the 1.5 L in the 2022 and newer Civic, and the related CR-V engines. Honda's diagnostic training material for the 2017 to 2023 Accord and the 2022 and newer Civic titles the code exactly: "DTC P055D: Rocker Arm Oil Pressure Sensor Circuit High Voltage."
On these engines "sensor B" is the rocker arm oil pressure sensor B. It sits on the cylinder head downstream of rocker arm oil control solenoid B, the VTEC solenoid. When the PCM commands VTEC, the solenoid opens and oil pressure builds in the rocker arm circuit to lock the high-lift rocker arm to its neighbors. The sensor reports that pressure back, so the PCM can confirm the switch happened. Older Honda engines used a simple oil pressure switch for this job and set P2646 through P2652 when it disagreed with the command. The turbo engines use a three-wire sensor that returns a proportional voltage, which is why the codes moved to the P055x family.
One detail that matters when you look for the sensor: the 1.5 L turbo exists with and without VTEC depending on the cylinder head. The twin-scroll head has VTEC on the exhaust side only and carries the rocker arm oil pressure sensor; the single-port head has no VTEC and no sensor B. If the engine has no second oil pressure sensor at all, P055D on a scan tool is a translation error and the code should be re-read with Honda definitions.
The set condition, in numbers
Honda's service information describes the monitor precisely, and the numbers explain the diagnosis:
With the engine running and engine speed at 4,000 rpm, the output voltage from rocker arm oil pressure sensor B is 4.79 V or higher for at least 2 seconds.
Two things follow from that:
- The test runs at high engine speed. The PCM checks the sensor when VTEC is active or about to be, which means the code cannot set at idle. A vehicle that idles all day in a driveway will never store it. That is not a sign that the fault is gone; it is a sign the monitor has not run. Read the freeze frame to see the engine speed and coolant temperature at the moment it set, and reproduce that condition on the road test.
- 4.79 V is the top of the range. A three-wire sensor gets a 5-volt reference, a ground and returns a signal between them. A healthy sensor never reaches 4.79 V, because that would represent more oil pressure than the circuit can produce. The signal only gets there when the sensor is not pulling it down: an open signal wire, an open ground, or a sensor with a failed element. Each of those leaves the signal line floating up toward the reference. In other words, P055D is an open-circuit code dressed as a high-reading code.
Causes, in the order Honda's own list puts them
Honda's probable-cause list for this code, reproduced by technicians who work from the service information, reads in this order:
Poor connections or loose terminals at rocker arm oil pressure sensor B and at the PCM. The sensor connector sits on the cylinder head in engine heat, and the seal ages. A terminal that has backed out of the connector body or spread from an earlier probe gives an intermittent open that shows up only at 4,000 rpm when the engine rocks on its mounts.
An open circuit between the PCM and the sensor. The signal wire or the ground wire broken somewhere in the harness. A JustAnswer Honda technician working a 2018 Accord with this code noted a cause that is easy to overlook: a serpentine belt that has shredded and whipped the nearby harness, cutting or abrading a wire. If the belt has recently been replaced, or there is any sign of belt debris in the engine bay, inspect the harness in that path before anything else.
A faulty rocker arm oil pressure sensor B. The sensor element fails open, or oil migrates through the sensor body into the connector. Honda has a long history of oil pressure switches and sensors on this circuit leaking oil into the connector and up the harness by capillary action, which corrupts the signal and eventually the connector. Oil in the connector when you unplug it is a diagnosis, not a curiosity.
The PCM needs a software update, or has failed. Listed last, and Honda includes the update step because some early calibrations set the code too readily. Check for an available PCM update before condemning any hardware, and replace the PCM only after every wire has been measured and a known-good sensor has been tried.
A diagnostic order that respects the numbers
- Record the code and its companions before clearing. P055D alone points at the sensor B circuit. P055D with P2646 or P2647 family codes, or with a VTEC solenoid code, means the fault may be upstream in the solenoid circuit. Check whether the code is current or history and pull the freeze frame.
- Confirm the engine has a sensor B. Locate the rocker arm oil pressure sensor on the cylinder head near the VTEC solenoid. If this 1.5 L has the single-port head, there is no VTEC and no sensor B, and the code is a tool translation error.
- Open the connector and look. Oil inside the connector, corrosion, a pushed-back terminal, or a wire that has been cut or abraded by a belt each explains the code by itself. Clean or repair before measuring, because a contaminated connector fails every test.
- Measure at the sensor connector, key on, sensor unplugged. About 5 V on the reference pin. Under 0.1 V of drop on the ground pin to battery negative. On most Honda PCMs, roughly 5 V on the signal pin as well, because the PCM holds the signal line up through a pull-up resistor; that pull-up is why an open circuit reads high. No reference voltage means the fault is upstream, on a circuit that other sensors may share.
- Check the signal and ground wires end to end. With the PCM connector disconnected, continuity from the sensor connector to the PCM connector on each wire should be under an ohm, with no short to the reference wire. Flex the harness along its route, especially past the belt path, while measuring.
- Watch the sensor live. Reconnect, start the engine, and watch the rocker arm oil pressure sensor B voltage on the scan tool. It should sit low at idle and rise when VTEC is commanded at higher engine speed. A signal parked at 4.79 V or above with the engine running is the live fault.
- Check for a PCM update, then substitute a sensor only if the wiring passed. Confirm the fix on the road with a run to 4,000 rpm in a lower gear, held for a few seconds, and then let the readiness monitors complete.
What P055D does not tell you
It does not mean the engine has high oil pressure, and it does not mean the main oil pressure sensor is bad. It names a monitoring sensor on the VTEC circuit and says its signal was pinned high, which is what an open circuit looks like to a PCM. It does not distinguish a corroded connector from a cut wire from a failed sensor, and it does not say whether the fault is present now. The connector and a voltmeter separate those. The sensor comes last because it is the component that can be tested by measurement rather than replaced on faith; the general principle is covered in what a trouble code does not tell you.
Frequently asked questions
Can I drive with a P055D code?
Yes. The code concerns a sensor that monitors the VTEC oil circuit, not the engine's main oil pressure. The PCM usually disables the high-lift mode as a precaution, so the engine feels slightly flat above 4,000 rpm and the check engine light stays on. It should still be diagnosed, because an open on this circuit often means a connector or harness problem that will spread.
Does P055D mean my oil pressure is too high?
No. On the Hondas that set this code, sensor B is the rocker arm oil pressure sensor that watches VTEC oil pressure. A signal at 4.79 V or above is the top of the sensor's range, which a healthy sensor never reaches. That reading means an open signal wire, an open ground or a failed sensor, not an engine with excessive pressure.
Why did P055D set only after I drove hard?
Because Honda's monitor for this code runs at 4,000 rpm, when the PCM checks whether VTEC oil pressure has built. The fault cannot set at idle. If a scan shows the code as history only, reproduce the condition on the road test rather than concluding the problem has gone away.
How much does it cost to fix P055D?
A connector cleaning or a harness repair is usually under an hour of labor. A rocker arm oil pressure sensor on a Honda is a modest part with a short replacement time, and it is worth replacing any connector that has oil inside it at the same time. A PCM is the expensive outcome, and Honda's procedure puts it last, after a software update check and a full round of wiring tests.
Related codes
- P055B / P055C / P055E: oil pressure sensor B range or performance, low signal and intermittent. The same circuit failing in a different direction; P055C is the mirror of this code and points at a short to ground or a sensor pulled low.
- P2646 / P2647: rocker arm actuator system performance and stuck on. The VTEC mechanism did not respond to the command. On older Hondas these were the codes the oil pressure switch set; on the turbo engines they can accompany P055D when the solenoid circuit is also at fault.
- P2651 / P2652: rocker arm oil pressure switch B circuit low and high, the older switch-type codes for the same job.
- P0520 through P0523: engine oil pressure sensor or switch A circuit, the main oil pressure sensor that runs the warning light. Not the same sensor.
The code number itself tells you the family and the domain; how to read an OBD2 code number explains what each character means and why the D in P055D is a hexadecimal digit, not a letter.