P2652 on 2017 Acura TLX 3.5L V6: Causes and Fixes for Rocker Arm Oil Pressure Switch Failure

What's Unique About the 2017-2017 Acura TLX

This code is specific to Honda and Acura vehicles equipped with the J-series V6 engine featuring Variable Cylinder Management (VCM). The engine uses multiple oil pressure switches: 'A' switches monitor VTEC operation, while the 'B' switch specifically monitors the VCM system. P2652 points to the 'B' switch on Bank 1 (the rear cylinder bank), which is the only bank that has a 'B' switch because VCM deactivates the rear cylinders to improve fuel economy. A failure in this switch directly impacts the engine's ability to seamlessly switch between 3-cylinder and 6-cylinder modes.

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 Light) is on
• Rough running engine or rough idle.
• Vehicle may enter 'limp mode', with reduced engine power and speed.
• Audible ticking or tapping noise from the engine.
• Vehicle may refuse to start or stall immediately after starting.

Most Likely Causes

1. Faulty Rocker Arm Oil Pressure Switch 'B' (Bank 1) 🔴 High Probability This specific pressure switch is noted in forums and by technicians to have a very high failure rate on Acura and Honda V6 engines, often failing internally and creating a short circuit.
   How to confirm: After checking oil level and wiring, the most definitive test is to check for continuity between the switch's electrical pin and a body ground with the connector unplugged and engine off. If continuity exists, the switch is internally shorted and has failed. Replacement is the standard fix.
   Typical fix: Replace the Rocker Arm Oil Pressure Switch 'B' for Bank 1. This switch is located on the rear cylinder head (closer to the firewall). A 24mm deep socket is required for removal.
   Est. part cost: $40-$80
2. Low Engine Oil Level or Incorrect Oil Type 🟡 Medium Probability The VCM system is highly sensitive to oil level and pressure. Low oil levels are a common cause for VCM-related diagnostic trouble codes like P3400 and P3497, which are functionally related to P2652.
   How to confirm: Check the engine oil dipstick to ensure the level is between the minimum and maximum marks. Verify that the oil viscosity matches the manufacturer's recommendation (usually found on the oil cap or in the owner's manual).
   Typical fix: Perform an oil and filter change with the correct grade of oil and a quality filter. Clear codes and re-test.
   Est. part cost: $40-$100
3. Damaged Wiring or Connector ⚪ Low Probability
   How to confirm: Visually inspect the wiring harness and connector leading to the Bank 1 Rocker Arm Oil Pressure Switch 'B' for any signs of damage, corrosion, or loose connections. The switch is on the rear cylinder head, so access may be tight. Check for reference voltage at the connector with the key on.
   Typical fix: Repair or replace the damaged section of the wiring harness or the connector.
   Est. part cost: $10-$50

Rare But Worth Checking

• Clogged Oil Passages: Sludge or debris from infrequent oil changes can clog the small passages leading to the VCM solenoid and pressure switch, causing erratic pressure readings. This is a known long-term concern on VCM-equipped engines. An engine flush may help, but replacing the entire VCM spool valve assembly is often required in severe cases.
• Faulty Powertrain Control Module (PCM): This is extremely rare. The PCM should only be considered after all other possibilities, including the switch, oil, and wiring, have been thoroughly ruled out.

Diagnosis Steps

1. Check the engine oil level and condition. If it is low, dirty, or the wrong viscosity, correct this first, clear the codes, and see if the problem returns. This is the first step recommended in official service bulletins.
2. Inspect the electrical connector and wiring for the Bank 1 Rocker Arm Oil Pressure Switch 'B'. It is located on the rear cylinder head, often with a brown or green connector. Check for damage, corrosion, or a loose fit.
3. Perform an electrical test on the switch. Disconnect the connector and, using a multimeter, check for continuity between the single pin on the switch and a good engine ground. With the engine off, there should be NO continuity. If there is continuity, the switch has failed and must be replaced.
4. If the oil, wiring, and switch test are all good, the issue may be mechanical. A VCM system oil pressure test using a specialized gauge can check for blockages in the oil passages, though this is less common.
5. Due to the extremely high failure rate and low cost of the part, many technicians and DIYers opt to replace the switch as a primary diagnostic step after confirming the oil level is correct.

Parts You'll Likely Need

• Rocker Arm Oil Pressure Switch B (Bank 1) (OEM #37240-R70-A04) — This switch is the primary cause for code P2652. It fails internally, sending a continuous 'stuck on' signal (short to ground) to the engine computer. This part number supersedes 37240-R70-A03 and 37240-R70-A02.
  Trusted brands: Genuine Acura/Honda, Standard Motor Products (PS499), Duralast (PS702)
  OEM price range: $50-$80
  Aftermarket price range: $30-$60
• Oil Pressure Switch O-Ring (OEM #91319-PAA-A01) — This O-ring provides the seal for the pressure switch. It is critical to replace it to prevent oil leaks after the repair. It is often sold separately.
  Trusted brands: Genuine Acura/Honda
  OEM price range: $2-$5
  Aftermarket price range: $1-$3

Related Codes That Often Appear With This One

• P3400 — P3400 means 'Valve Pause System (VPS) Stuck Off Bank 1'. Since P2652 indicates a problem with the pressure switch that monitors this exact system, the two codes frequently appear together. An official Acura TSB lists these two codes as a common pair requiring investigation.

Technical Service Bulletins (TSBs) & Recalls

• BTI&01192022901: A request from Acura to dealerships to inspect vehicles with P2652 and P3400 to better understand the root cause, indicating manufacturer awareness of the issue for the 2017 TLX within a specific VIN range.
• Honda TSB 13-031: While for slightly older models, this bulletin addresses the same VCM codes (P3400/P3497) and identifies the cause as an intermittently failing rocker arm oil pressure switch, recommending its replacement. This confirms the long-standing nature of this part failure.

Platform-Specific Known Issues

• Acura issued a Technical Service Bulletin, #BTI&01192022901, acknowledging that they were investigating 2017 TLX models with VINs between 19UUB….HA002327 and 19UUB….HA900123 for setting codes P2652 and P3400.
• The underlying Variable Cylinder Management (VCM) system on this engine is a point of controversy among owners. It is associated with long-term issues like increased oil consumption and fouled spark plugs. Some owners proactively install an aftermarket 'VCM Muzzler' or 'VCM Tuner' to disable the system and avoid these problems, though this is a modification and not a direct fix for a failed switch.

Mechanic-Grade Diagnostic Values

• Rocker Arm Oil Pressure Switch 'B' (Bank 1) Signal Wire Voltage — expected: Approximately 0V when VCM is active (3-cylinder mode) and battery voltage when VCM is inactive (6-cylinder mode).. Failure: A reading of 0V or near 0V when the engine is in 6-cylinder mode indicates the switch is stuck 'On' (shorted to ground), triggering P2652.
• VCM System Oil Pressure at Switch Port — expected: Greater than 45 kPa (6.5 psi) when the VCM system is commanded on.. Failure: Pressure below 45 kPa (6.5 psi) when the system should be active points to a mechanical issue like a clogged oil passage or a faulty VCM solenoid, not the switch itself.

Scan Tool Commands That Help

• Honda HDS (Honda Diagnostic System) or equivalent bidirectional scanner: VCM System Test or Cylinder Deactivation Test — This function allows a technician to manually command the VCM system on and off while monitoring the live data from the 'B' pressure switch. This can definitively confirm if the switch is responding to actual pressure changes or if it is stuck electrically, without having to wait for specific driving conditions.

Wiring & Ground Locations

• G101 (example, specific to model generation) — A primary engine-to-chassis ground is typically located near the passenger side motor mount or near the transmission mount, under the battery tray area.. The pressure switch is a single-wire sensor that grounds through the engine block. A poor engine ground can cause floating voltages and erratic sensor readings for multiple components, including the VCM pressure switch. Verifying the main engine ground strap is clean and tight is a crucial step in diagnosing any electrical fault.
• Rocker Arm Oil Pressure Switch 'B' Connector — On the rear cylinder head (Bank 1), often with a brown or green single-wire connector.. This is the direct connection point for testing. The wire (often labeled VCMSW) runs from this connector to the Powertrain Control Module (PCM). A short-to-ground in this wire can mimic a failed switch.

Real Owner Repair Stories

• AcuraZine Forum User (2017 Acura RDX (same 3.5L V6 and VCM system)) — Sudden limp mode, flashing check engine light, shuddering, and inability to accelerate.
  ❌ Tried (didn't work) The owner initially suspected a transmission failure due to the shuddering and limp mode.
  ✅ What actually fixed it The dealership diagnosed code P2652 and replaced the Rocker Arm Oil Pressure Switch 'B' on Bank 1. This single repair resolved all symptoms, including the limp mode and poor performance.
• AcuraZine Forum User (2016 Acura MDX (same 3.5L V6 and VCM system)) — Check Emission System light, limp mode, strong gasoline smell from exhaust.
  ❌ Tried (didn't work) The owner was unable to physically reach the rear switch to test it.
  ✅ What actually fixed it The user unplugged the electrical connector to the switch, drove the vehicle, then plugged it back in and cleared the codes. The issue did not immediately return, suggesting a possible intermittent connection issue or a switch on the verge of failure. While not a definitive repair, this points to the switch/connector as the source of the problem.

OEM Part Supersession History

• 37240-R70-A02, 37240-R70-A03 → 37240-R70-A04 — Part revisions are common to improve reliability and address known failure modes. The -A04 version is the latest revision intended to be more durable than its predecessors.
  Heads up: The latest part number, 37240-R70-A04, is fully backward compatible with vehicles that used the -A02 and -A03 versions.