P2652 on 2017 Acura MDX: Rocker Arm Oil Pressure Switch Failure Causes and Fixes

What's Unique About the 2017-2017 Acura MDX

The 3.5L V6 engine (J35Y5) in the 2017 MDX uses Honda's Variable Cylinder Management (VCM) system to improve fuel economy by shutting down the rear bank of cylinders (Bank 1) during light-load cruising. Code P2652 specifically relates to the oil pressure switch that monitors this VCM function on Bank 1. This particular switch has a very high failure rate across many Honda and Acura models with the J-series V6 engine, leading Acura to issue a Technical Service Bulletin (TSB) to investigate the issue. The 'B' switch is for the VCM system, while the 'A' switch monitors the VTEC system.

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) is on, sometimes flashing
• Vehicle enters 'limp mode,' resulting in a significant lack of acceleration and power
• Engine may run rough, judder, or hesitate, particularly during light acceleration
• Variable Cylinder Management (VCM) system will be disabled, potentially leading to a decrease in fuel economy.

Most Likely Causes

1. Failed Rocker Arm Oil Pressure Switch (Bank 1) 🔴 High Probability This specific switch is a known high-failure part on Honda/Acura J-series V6 engines, with technicians reporting they replace them frequently. A TSB (BTI&01192022901) was issued by Acura to investigate this exact problem, confirming it's a recognized issue. The failure is often internal to the switch.
   How to confirm: The most definitive way is to replace the switch, as testing can be inconclusive. A technician can use a scan tool to monitor the switch's voltage to see if it changes state as expected. A visual inspection may reveal oil has leaked from the switch body itself into the electrical connector, which is a sure sign of failure.
   Typical fix: Replace the Rocker Arm Oil Pressure Switch for Bank 1. The part number is 37240-R70-A04, which supersedes 37240-R70-A03 and 37240-R70-A02.
   Est. part cost: $40-$80
2. Low or Dirty Engine Oil 🟡 Medium Probability The VCM system is hydraulic and highly sensitive to oil level, viscosity, and cleanliness. Using the wrong oil or extending oil change intervals can lead to sludge or debris that can clog passages or cause the switch to stick.
   How to confirm: Check the engine oil dipstick for proper level and inspect the oil's condition. If it is very dark, gritty, or below the minimum mark, this could be the cause. This should always be the first check.
   Typical fix: Perform an oil and filter change using the manufacturer-recommended oil type and weight (typically full synthetic 0W-20 for this model). In some cases, this alone can resolve the code.
   Est. part cost: $40-$90
3. Wiring or Connector Issue ⚪ Low Probability
   How to confirm: Visually inspect the wiring harness and connector going to the oil pressure switch. A common issue is the failed switch leaking oil into the connector, causing a poor connection or short. Check for any signs of damage, corrosion, or loose pins. A multimeter can be used to check for a short in the wire between the switch and the PCM.
   Typical fix: If oil is present, clean the connector thoroughly with electrical contact cleaner. If the wiring is damaged, repair the affected section. If the connector itself is damaged, it will need to be replaced.
   Est. part cost: $5-$50

Rare But Worth Checking

• Faulty Powertrain Control Module (PCM):

Diagnosis Steps

1. Verify the engine oil level and condition. Top off or change the oil and filter if necessary. This is the easiest and most important first step.
2. Scan the computer for any other trouble codes. Note if P3400 is also present, as this strongly points to the VCM system on Bank 1.
3. Locate the Rocker Arm Oil Pressure Switch 'B' for Bank 1. On the 3.5L V6, Bank 1 is the rear bank, closer to the firewall. The 'B' switch for the VCM system is typically the one closer to the intake manifold. Access can be tight.
4. Disconnect the electrical connector from the switch. Inspect the connector and the switch port for any oil contamination. A failed switch often leaks oil into the connector.
5. If oil is found in the connector, the switch is bad. Clean the connector with electrical contact cleaner before installing the new switch.
6. Given the high failure rate and low cost of the part, the most common and time-effective step is to replace the switch (Part No. 37240-R70-A04). A 24mm deep socket or wrench is typically required.
7. After replacement, clear the codes using a scan tool and perform a test drive, including light-load cruising, to ensure the code does not return.

Parts You'll Likely Need

• Rocker Arm Oil Pressure Switch (Bank 1, VCM) (OEM #37240-R70-A04) — This is the component that the code directly identifies as being 'stuck on'. It is a very common failure point on this engine, as documented in owner forums and a manufacturer TSB.
  Trusted brands: Acura (Genuine OEM), Honda (Genuine OEM), Standard Motor Products (Aftermarket), NTK (Aftermarket)
  OEM price range: $60-$80
  Aftermarket price range: $30-$50

Related Codes That Often Appear With This One

• P3400 — P3400 means 'Valve Pause System (VPS) Stuck Off Bank 1'. Since P2652 indicates the pressure switch for this same system is stuck on, the computer sees a conflicting state. Acura's TSB BTI&01192022901 explicitly links these two codes as appearing together, strengthening the diagnosis of a Bank 1 🎬 See how to diagnose and repair codes P3400 and P2652 VCM system fault.

Technical Service Bulletins (TSBs) & Recalls

• BTI&01192022901: AHM is searching for 2017 MDXs, RDXs, RLXs & TLXs with a client complaint of the Malfunction Indicator Light (MIL) on with the DTC P2652 (Rocker Arm Oil Pressure Switch B [Bank 1] Stuck On) & P3400 (Valve Pause System [VPS] Stuck Off Bank 1) stored.

Platform-Specific Known Issues

• Acura TSB BTI&01192022901 - Data Gathering: Acura issued this bulletin specifically to investigate 2017 MDX models (among others) that store DTC P2652 and P3400. This was not a recall, but a request for dealerships to capture data from affected vehicles before performing repairs, to help Honda's engineers better understand the root cause of the switch failure.
• Real-World Repair Story: An owner of a 2017 RDX (a platform mate) on AcuraZine experienced a flashing check engine light and the car entering limp mode. The dealership diagnosed code P2652, replaced the rocker arm oil pressure switch, and the issue was resolved. This is a typical owner experience with this specific fault code.

Mechanic-Grade Diagnostic Values

• Rocker Arm Oil Pressure Switch B (Bank 1) Voltage — expected: Fluctuating around 0.5V with engine running.. Failure: A reading of zero volts with the key on or an unchanging voltage when the engine is running could indicate a wiring or switch issue.
• VCM System Oil Pressure at Switch Port — expected: 45 kPa (6.5 psi) or more.. Failure: Pressure below this threshold indicates a problem with oil passages or the rocker arm oil control valve, not the switch itself.
• Rocker Arm Oil Pressure Switch B (Bank 1) Continuity — expected: No continuity between the switch terminal and ground when oil pressure is below the threshold.. Failure: Continuity present when there should be none indicates the switch is stuck internally.

Scan Tool Commands That Help

• Honda Diagnostic System (HDS): Snapshot function / Data List — To monitor the live data from the rocker arm oil pressure switch and other ECM/PCM parameters in real-time to see if the switch is changing state as expected under different driving conditions.
• Honda Diagnostic System (HDS): Jump the SCS line — A service manual procedure mentions jumping the Service Check Connector (SCS) line with the HDS as part of a diagnostic reset or check, which may be required after certain troubleshooting steps.

Wiring & Ground Locations

• Rocker Arm Oil Pressure Switch B (Bank 1) — On the rear cylinder bank (Bank 1), which is closer to the firewall. The 'B' switch for the VCM system is the one closer to the intake manifold, often with a brown electrical connector.. This is the physical location of the component identified by code P2652. Correctly identifying Bank 1 and the 'B' switch is critical to avoid replacing the wrong part.
• PCM Connector C (51P), Pin 34 — This is one of the main connectors at the Powertrain Control Module (PCM).. Pin 34 is the specific terminal for the VCMSW (VCM Switch) line. Technicians can test for a short to ground or check for continuity between this pin and the switch connector to diagnose wiring faults.

Real Owner Repair Stories

• Reddit user on r/accord (2019 Honda Accord Touring 2.0 (different engine, but same code logic)) — Pending P2652 code after hard acceleration (WOT). Engine sounds louder/raspier and drives poorly at low RPMs, as if stuck in VTEC.
  ❌ Tried (didn't work) Replaced the entire spool valve assembly (part #15810-6B2-A01), which included the oil pressure sensor, switch, and filter.
  ✅ What actually fixed it The user was still diagnosing, with the next step being to inspect the wiring connectors. This story is valuable because it shows that even replacing the entire assembly doesn't always fix the issue, pointing towards a potential wiring or PCM problem.
• AcuraZine user 'thoiboi' (2017 Acura RDX Tech) — Vehicle went into limp mode with flashing check engine light and juddering/shuddering while driving.
  ❌ Tried (didn't work) Owner initially suspected a transmission failure.
  ✅ What actually fixed it The dealership diagnosed code P2652 and resolved the issue by replacing the rocker arm oil pressure switch for Bank 1. They also performed a transmission fluid flush and firmware update for a separate shuddering issue.

When the Usual Fixes Don't Work

• While the most common fix is replacing the oil pressure switch, there are documented cases where this does not solve the problem. In one instance involving a similar Honda engine, an owner replaced the entire spool valve assembly, which includes the switch and a new filter screen, but the P2652 code persisted. This suggests that in some scenarios, the root cause is not the switch or its immediate assembly, but rather a wiring issue between the switch and the PCM, or a fault within the PCM itself. Therefore, if a new switch doesn't work, the next step should be a thorough inspection of the wiring harness for continuity and shorts before condemning the expensive PCM.