P2651: Rocker Arm Actuator B Performance/Stuck Off (Meaning, Causes, Fixes)
What P2651 means
Some engines use oil pressure to switch the rocker arms, and so the valve timing or lift, between modes. Honda's VTEC system is the best-known example. P2651 has the generic definition "B" Rocker Arm Actuator System Performance/Stuck Off, the "B" counterpart of P2646. The two sources explain it differently. RepairPal says newer engines use variable valve lift, with position sensors inside the variable lift rocker arm assembly so the PCM can monitor what it is doing; its P2651 page then says a failed sensor sets code P264C, which looks like text reused from another code, so this page does not rely on that sentence. Honda's service bulletin 13-021 lists P2646/P2651 together as rocker arm oil pressure switch circuit low voltage, and P2647/P2652 as circuit high voltage, and says the rocker arm oil pressure switch may fail intermittently. The bulletin does not explain what separates P2651 from P2646 on the covered Hondas; it gives the same fix for both. Honda also notes the problem may be intermittent and may not come back right after the code is cleared.
Severity: can I keep driving?
Stop and fix promptly
Get it checked soon. RepairPal rates P2651 as Urgent. Honda's service bulletin 13-021 lists P2651 alongside P2646 as a rocker arm oil pressure switch circuit low voltage fault, caused by a switch that can fail intermittently. Because low engine oil is a listed cause for the matching "A" code, check the oil level before driving further. If the oil is low or the oil pressure light comes on, stop and don't drive until it is fixed, since running an engine low on oil can damage it.
Common symptoms
- Check engine light on (Honda bulletin 13-021)
- The fault may be intermittent and may not return right after the code is cleared (Honda bulletin 13-021)
- Neither source lists drivability symptoms specific to P2651; for the matching "A" code P2646, RepairPal lists decreased performance and higher fuel consumption
Likely causes
Roughly most to least common, based on the sources below. Your vehicle may differ.
- A failed rocker arm oil pressure switch, which Honda says can fail intermittently (Honda bulletin 13-021)
- A failed sensor inside the variable lift rocker arm assembly (RepairPal's general explanation)
- Wiring or connector problems in the switch or sensor circuit (a general electrical cause; RepairPal lists wiring for the matching "A" code P2646)
- Low engine oil level (RepairPal lists this for the matching "A" code P2646, so rule it out first)
Diagnostic steps you can do
Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.
- Check the engine oil level and condition first, and top it up with the correct oil if it is low.
- Read all stored codes and note whether P2646, P2647 or P2652 are also set.
- Find the rocker arm oil pressure switch (on the cylinder head near the valve cover on many Hondas) and check its connector and wiring for damage, oil soaking or a loose fit.
- Check for technical service bulletins for your vehicle. Honda bulletin 13-021 covers P2651 on the 2003-12 Accord 4-cylinder, 2002-05 Civic Si, 2012-13 Civic (except Si and Hybrid), 2002-09 CR-V, 2011 CR-Z, 2003-11 Element and 2007-11 Fit.
- Clear the code and see whether it returns; Honda notes it may be intermittent.
Typical fixes
- Replace the rocker arm oil pressure switch and its O-ring; on the Hondas covered by bulletin 13-021 this is the stated fix, with the switch torqued to 22 N-m (16 lb-ft)
- Top up or change the engine oil if it is low or the wrong type
- Repair damaged wiring or connectors in the switch circuit
- If the code returns after the switch is replaced, follow the factory troubleshooting procedure for the code, as Honda's bulletin directs
Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.
🛠 When to call a pro
- The oil level is fine and a new switch didn't fix it
- The oil pressure light comes on or the engine makes new ticking or knocking noises
- Several valve timing codes are set at once
- Your vehicle is covered by Honda bulletin 13-021 and is still under warranty
Where to buy
Plain search links. Always match parts to your exact year, make, model and engine.
FAQs
Is P2651 serious?
RepairPal rates it Urgent. On many Hondas the cause is an intermittent rocker arm oil pressure switch (Honda bulletin 13-021), but check the oil level right away and don't drive if it is low or the oil pressure light is on.
What is the most common fix for P2651 on a Honda?
Honda's service bulletin 13-021 says the rocker arm oil pressure switch may fail intermittently and directs replacing it with a new O-ring, on the 2003-12 Accord 4-cylinder, 2002-05 Civic Si, 2012-13 Civic (except Si and Hybrid), 2002-09 CR-V, 2011 CR-Z, 2003-11 Element and 2007-11 Fit.
What is the difference between P2651 and P2646?
Generically, P2646 refers to the "A" rocker arm actuator system and P2651 to the "B" system. Honda's bulletin groups them together as rocker arm oil pressure switch circuit low voltage and gives the same fix for both, without explaining the difference on the covered models.
How much does it cost to fix P2651?
None of the sources gives a repair cost. Honda's bulletin lists 0.3 to 0.5 hours of labor to replace the switch on the covered models, but parts prices and shop rates vary, so get a written estimate.
Sources
Last reviewed 2026-10-24. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.