P2652 on 2017 Acura RLX: Rocker Arm Oil Pressure Switch 'B' Stuck On Causes and Fixes

What's Unique About the 2017-2017 Acura RLX

On the Acura 3.5L V6 engine, this code is specifically tied to the Variable Cylinder Management (VCM) system, which Acura sometimes refers to as the Valve Pause System (VPS). The 'B' switch monitors the oil pressure used to deactivate the rear bank of cylinders (Bank 1). These systems are known to be sensitive to oil level and quality, as the solenoids and switches rely on clean oil to function correctly. The high frequency of cylinder deactivation and reactivation in normal driving puts significant cyclical stress on this particular switch, leading to a high failure rate across many Honda and Acura models with the J-series V6 engine. A technical service bulletin (TSB) was issued by Acura for this exact code on 2017 models, indicating it's a known issue the manufacturer is tracking.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Check Engine Light (Malfunction Indicator Lamp or MIL) is on
• Engine running rough or idling erratically
• Vehicle enters 'limp mode', limiting engine power and speed
🎬 See how to fix limp mode caused by code P2652
• Reduced fuel economy
• Strong smell of gasoline from the exhaust
• Audible ticking or tapping noise from the engine bay

Most Likely Causes

1. Low or Dirty Engine Oil 🔴 High Probability Acura's VCM system relies on clean oil and precise pressure to function. Low levels or degraded oil can cause pressure issues and sludge, leading to switch and solenoid malfunctions. Using non-OEM oil filters has also been anecdotally linked to this issue in forums.
   How to confirm: Check the engine oil dipstick for proper level and inspect the oil's color and consistency. If it's low, dark, or sludgy, it needs to be changed.
   Typical fix: Perform an oil and filter change using the correct viscosity oil specified for your vehicle (e.g., 0W-20). Use a quality OEM or equivalent oil filter. Reset the code and see if it returns.
   Est. part cost: $40-$80
2. Faulty Rocker Arm Oil Pressure Switch 'B' (Bank 1) 🔴 High Probability Forum discussions and mechanic reports indicate a very high failure rate for this specific pressure switch on Acura's J-series V6 engines due to VCM-related wear. The internal diaphragm fails, causing it to get stuck.
   How to confirm: After confirming oil level is correct, the next step is to test the switch. This can involve checking for continuity with a multimeter or using a scan tool to monitor its live data. However, given the high failure rate and low part cost, many owners and technicians choose to replace it as the primary diagnostic step after an oil change fails to resolve the code.
   Typical fix: Replace the Bank 1 Rocker Arm Oil Pressure Switch 'B' and its associated gasket. The recommended replacement part is the superseded OEM number 37250-R70-A04.
   Est. part cost: $40-$75
3. Wiring or Connector Issue ⚪ Low Probability
   How to confirm: Visually inspect the wiring harness and connector leading to the pressure switch for any signs of damage, corrosion, or loose connections. The connector is often brown. Use a multimeter to check for a short or open in the circuit.
   Typical fix: Repair the damaged wiring or clean/replace the connector.
   Est. part cost: $5-$50

Rare But Worth Checking

• Clogged VCM Oil Passages or Faulty Solenoid: If the oil is dirty or has been neglected, sludge can build up in the small oil passages of the VCM system or cause the control solenoid to stick. This is more serious and requires more extensive cleaning or component replacement.
• Low Battery Voltage: In some forum-reported cases, a failing battery has caused multiple, seemingly unrelated error codes to appear, including VCM-related codes. Before extensive repairs, ensure the battery and charging system are healthy.
• Faulty Engine Control Module (ECM): This is extremely rare. The ECM should only be considered after all other possibilities, including mechanical faults and wiring, have been exhaustively ruled out.

Diagnosis Steps

1. Verify the engine oil level and condition. Top up or change the oil and filter if necessary. Use the manufacturer-recommended oil type and viscosity (typically 0W-20).
2. Clear the trouble codes and test drive the vehicle to see if the code returns. If it doesn't, the issue was likely the oil.
3. If the code returns, locate the Rocker Arm Oil Pressure Switch 'B' on Bank 1. On the 3.5L V6, Bank 1 is the rear cylinder bank, closer to the firewall. The switch is often identified by a brown electrical connector.
4. Inspect the switch's electrical connector and wiring for any visible damage, corrosion, or loose connections.
5. Test the switch for continuity. When the engine is off, there should be no continuity between the switch's terminal and ground. If there is continuity, the switch is stuck 'on' and must be replaced.
6. To replace the switch, you will typically need a 24mm deep well socket and an extension.
🎬 Watch this walkthrough on replacing oil pressure switches
7. If the switch and wiring test good, the issue may be a clogged oil passage or a faulty VCM solenoid, which requires more advanced diagnostics, including checking oil pressure at the switch port with a gauge.

Parts You'll Likely Need

• Rocker Arm Oil Pressure Switch 'B' (Bank 1) (OEM #37250-R70-A04 (This supersedes 37250-R70-A03)) — This switch is the most common point of failure for code P2652. It gets stuck internally, sending a constant 'on' signal to the ECM. The -A04 version is the updated, more reliable part.
  Trusted brands: Genuine Acura/Honda, Standard Motor Products, NTK
  OEM price range: $60-$90
  Aftermarket price range: $40-$75
• Rocker Arm Oil Pressure Switch Gasket/O-Ring (OEM #91319-PAA-A01) — It is highly recommended to replace the small gasket or O-ring when replacing the switch to prevent oil leaks. Many aftermarket switches include it, but it should be verified.
  Trusted brands: Genuine Acura/Honda
  OEM price range: $2-$5
  Aftermarket price range: $1-$3
• Engine Oil and Filter — Incorrect oil level or poor oil quality is a primary cause of VCM system faults. An oil change is the first diagnostic step.
  Trusted brands: Mobil 1, Castrol, Valvoline
  OEM price range: $60-$100
  Aftermarket price range: $40-$80

Related Codes That Often Appear With This One

• P3400 — Acura's TSB #BTI&01192022901 explicitly links P2652 with P3400 🎬 Watch: How to replace the oil pressure switch for code P3400 ('Valve Pause System [VPS] Stuck Off Bank 1'). They relate to the same VCM system malfunction on Bank 1, so they frequently appear together as a pair.

Technical Service Bulletins (TSBs) & Recalls

• BTI&01192022901: Acura requested dealership assistance to inspect 2017 RLX, MDX, RDX, and TLX vehicles with client complaints of the MIL on and DTC P2652 and/or P3400 stored, sometimes with a rough running engine.

Platform-Specific Known Issues

• Acura issued TSB #BTI&01192022901, which is a 'Business and Technology Information' bulletin. This was a request for dealerships to collect information on 2017 RLX models (among others) storing codes P2652 and P3400. This indicates Acura was actively investigating a pattern of failure, rather than issuing a recall or specific repair campaign.

Mechanic-Grade Diagnostic Values

• Rocker Arm Oil Pressure Switch 'B' Continuity Test — expected: With the engine OFF (no oil pressure), there should be NO continuity between the switch's electrical terminal and the engine block (ground).. Failure: If continuity exists with the engine OFF, the switch is internally shorted or 'stuck on' and must be replaced.
• VCM System Oil Pressure at Switch Port — expected: At least 45 kPa (6.5 psi) when the VCM system is commanded on.. Failure: If pressure is below the specification, it indicates a blockage in the oil passages or a faulty VCM solenoid, not necessarily a bad pressure switch.
• Rocker Arm Oil Pressure Switch Installation Torque — expected: 22 N.m (16 lb-ft). Failure: Over-torquing can damage the switch or threads; under-torquing can cause oil leaks.

Scan Tool Commands That Help

• Honda HDS (or equivalent high-end scanner): VTEC+VCM TEST (specifically the CDVEB TEST) — This is a bidirectional test used to command the VCM system on and off. A technician can monitor the live data for the 'B' pressure switch to see if it changes state as commanded. If the command is sent to deactivate the system but the switch status remains 'On', it helps confirm the 'Stuck On' fault.

Wiring & Ground Locations

• Rocker Arm Oil Pressure Switch 'B' (Bank 1) — On the rear cylinder head (Bank 1), which is closer to the firewall. The switch is located on the VCM spool valve assembly and typically has a brown or black single-wire connector.. This is the specific component monitored by the P2652 code. Correctly identifying Bank 1 (rear) and Switch 'B' is critical to avoid replacing the wrong part.

Real Owner Repair Stories

• AcuraZine Forum User 'dyndragon' (2016 Acura MDX) — Limp mode, Check Emission System light, code P2652.
  ❌ Tried (didn't work) Initial self-diagnosis was uncertain between the two pressure switches.
  ✅ What actually fixed it A dealership diagnosis found the oil pressure switch was shorted to ground. They replaced the Bank 1 switch (Part No. 37240-R70-A04) and the O-ring (91319-R70-A01), which resolved the issue.
• Reddit User r/Honda (Honda with J-series V6 engine) — Pending P2652 code after wide-open throttle, engine sounds louder/raspier and runs poorly at low RPMs.
  ❌ Tried (didn't work) Replacing the entire spool valve assembly (which included a new switch and sensor) did not fix the problem; the code kept returning.
  ✅ What actually fixed it The user's issue was unresolved in the post, but it highlights a critical scenario where replacing the common parts does not work, pointing towards a more complex issue like a wiring harness problem or an intermittent mechanical fault.

OEM Part Supersession History

• 37240-R70-A01, 37240-R70-A02, 37240-R70-A03 → 37240-R70-A04 — The multiple revisions suggest Honda/Acura made improvements to the switch's internal diaphragm and construction to increase its reliability and prevent premature failure.
  Heads up: All previous versions are compatible but the -A04 part is the most current and recommended for replacement.