P0651 on 2016-2019 Buick Envision: Sensor Voltage 'B' Circuit Causes and Fixes

What's Unique About the 2016-2019 Buick ENVISION

What's unique to the Buick Envision and other GM vehicles of this era using the 2.5L LCV and 2.0L LTG engines is the strong link between P0651 and P06DE (Engine Oil Pressure Control Circuit Stuck On). A manufacturer Technical Service Bulletin (TSB) explicitly states that if both codes are present, the technician must diagnose the P06DE code first. This shifts the focus from a generic electrical hunt to specific, known mechanical failure points. These include debris from broken piston oil squirters contaminating the system (per TSB PIP5247A) or tiny foreign particles lodging in the oil pump's cold start checkball (per TSB PIP5676).

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 (Service Engine Soon lamp) is on
• Oil pressure warning light may be illuminated
• Reduced engine power or 'Engine Power is Reduced' message on dash
• Engine may run rough or make knocking/rattling noises
• Decreased fuel economy
• Tachometer (RPM gauge) may not work
• Service StabiliTrak message may appear

Most Likely Causes

1. Fault in the Engine Oil Pressure Control System (triggers P06DE) 🔴 High Probability Multiple GM Technical Service Bulletins (PIPs) document specific failure modes for the oil pressure system on these engines. The system is complex, involving a variable displacement oil pump. 🎬 See this breakdown of common causes for the P06DE code.
   How to confirm: Scan for other codes. If P06DE is present, follow the diagnostic procedure for that code first. This involves checking oil level/condition, testing the oil pressure sensor, and inspecting the oil pressure control solenoid and oil pump per TSB guidelines.
   Typical fix: Repairing the root cause of the P06DE code. This could be cleaning the oil pump checkball, replacing a broken piston oil squirter, or replacing the entire oil pump assembly.
   Est. part cost: $50-$400
2. Faulty Engine Oil Pressure Sensor 🟡 Medium Probability The oil pressure sensor is a key component on the 5-volt reference circuit. It can fail internally, causing a short or open that triggers P0651. It can also send incorrect readings that contribute to a P06DE code.
   How to confirm: Disconnect the sensor. If the 5-volt reference returns to normal on the circuit, the sensor is faulty. Test the sensor's resistance and compare it to specifications. Check live data on a scan tool to see if the pressure reading is logical.
   Typical fix: Replace the engine oil pressure sensor.
   Est. part cost: $30-$80
3. Wiring Harness Issue ⚪ Low Probability All vehicles are susceptible to wiring damage. A specific real-world example on a platform-mate involved the harness being crushed between the engine and transmission during a previous repair, causing a short.
   How to confirm: Visually inspect the wiring harness leading to the sensors on the 'B' reference circuit (especially the oil pressure sensor) for any signs of damage, corrosion, or loose connections. Use a multimeter to check for continuity and shorts to ground.
   Typical fix: Repair or replace the damaged section of the wiring harness.
   Est. part cost: $10-$100
4. Stuck or Dirty 'ECO' Mode Button ⚪ Low Probability On platform-mates like the Chevy Equinox, the ECO mode button is on a 5V reference circuit. If the switch gets gummed up with dirt or spilled liquids, it can cause a short or incorrect voltage reading, triggering P0651.
   How to confirm: If other symptoms like a non-working tachometer are present, try cleaning the ECO button assembly. A user on a forum reported that cleaning the sticky button with an ultrasonic cleaner resolved their P0651 code.
   Typical fix: Clean or replace the ECO mode switch.
   Est. part cost: $0-$50

Rare But Worth Checking

• Faulty Engine Control Module (ECM): This is extremely rare and should only be considered after all other possibilities, including all sensors and wiring on the circuit, have been thoroughly tested and ruled out.
• Improperly Installed Timing Chain Tensioner Gasket: A GM Preliminary Information bulletin notes that if major engine work was recently performed, an improperly installed timing chain tensioner gasket can cause an oil pressure leak, leading to low pressure and a P06DE code.

Diagnosis Steps

1. Connect an OBD-II scanner and check for all stored codes. Pay close attention if P06DE is present with P0651.
2. If P06DE is present, follow TSB #PIP5247A and diagnose P06DE first.
3. Check the engine oil level and condition. Ensure the correct oil type (e.g., 5W-30 full synthetic meeting GM standards) and a quality OEM-spec filter are being used. An incorrect filter can cause this issue.
4. Test the engine oil pressure mechanically to verify it is within specification.
5. If diagnostics lead to the oil pan (per TSB PIP5247A), inspect the oil pan and pickup tube for plastic or metal debris from a broken piston oil nozzle/squirter.
6. If diagnostics lead to the oil pump (per TSB PIP5676), inspect the cold start checkball for foreign material. Look very closely as the debris can be tiny.
7. If the engine has had recent major repairs, inspect the timing chain tensioner gasket to ensure it is not misaligned, causing an oil pressure leak.
8. If P0651 is present alone, identify all sensors on the 5V reference 'B' circuit using a service manual.
9. Disconnect sensors one by one, checking if the 5V reference returns to normal. The sensor that, when disconnected, restores the voltage is likely the faulty part.
10. Inspect wiring harnesses for damage, especially in areas where they might be pinched or chafed, such as between the engine and transmission.
11. Only suspect a faulty ECM after exhausting all other diagnostic steps.

Parts You'll Likely Need

• Engine Oil Pump / Balancer Assembly — May need to be replaced if debris is found internally that cannot be cleaned (per TSB PIP5676), or if the pump itself has failed, causing the P06DE code. The oil pump is integrated with the balance shaft assembly on the 2.5L LCV engine.
  Trusted brands: ACDelco, Melling
  OEM price range: $250-$450
  Aftermarket price range: $150-$300
• Engine Oil Pressure Control Solenoid — This solenoid, often located within the oil pump assembly, controls oil pressure and is a primary suspect for the related P06DE code. It can get stuck or fail electrically.
  Trusted brands: ACDelco, Dorman
  OEM price range: $60-$120
  Aftermarket price range: $40-$90
• Engine Oil Pressure Sensor — This sensor reports pressure to the ECM and is on the 5V reference circuit. It can fail and cause P0651 directly or be part of a P06DE fault.
  Trusted brands: ACDelco, Bosch, Standard Motor Products
  OEM price range: $40-$80
  Aftermarket price range: $25-$60
• Piston Oil Nozzle / Squirter — TSB PIP5247A indicates these can break apart, causing debris in the oil pan and leading to low oil pressure and the P06DE code. If one is found broken, it must be replaced.
  Trusted brands: ACDelco (GM Genuine)
  OEM price range: $15-$30

Related Codes That Often Appear With This One

• P06DE — According to GM TSB #PIP5247A, these codes often set together. P06DE indicates a problem with the oil pressure control circuit being stuck on, which can disrupt the 5-volt reference circuit and trigger P0651.
• P0521 — This code for 'Engine Oil Pressure Sensor/Switch Range/Performance' can also appear alongside P06DE, indicating a problem with the oil pressure readings. TSB PIP5676 mentions this code may set with P06DE.

Technical Service Bulletins (TSBs) & Recalls

• PIP5247A: Mentions that P0651 may set with P06DE and to follow diagnostics for P06DE first. Points to broken piston oil squirters as a potential root cause.
• PIP5676: Details a cause for P06DE where small debris gets caught in the oil pump's cold start checkball, requiring cleaning or pump replacement.
• GM PI #19-NA-004: A preliminary bulletin that warns of P06DE being caused by an improperly installed timing chain tensioner gasket after major engine repairs.

Platform-Specific Known Issues

• TSB PIP5247A: Broken Piston Oil Squirters: A known issue, documented in TSB #PIP5247A, is for P0651 to set with P06DE. The TSB advises technicians to inspect the oil pan for debris from broken piston oil nozzles (squirters) if diagnostics point to low oil pressure.
• TSB PIP5676: Debris in Oil Pump Checkball: TSB #PIP5676 notes that the cause for P06DE can be very small debris lodging in the oil pump's cold start checkball, which requires careful inspection of the oil pump assembly.

Mechanic-Grade Diagnostic Values

• Engine Oil Pressure Control Solenoid Resistance — expected: 10-18 Ohms. Failure: A reading of 0 Ohms indicates a short, while infinite resistance (OL) indicates an open circuit. A reading significantly outside the 10-18 Ohm range suggests a faulty solenoid.
• 5-Volt Reference Circuit Voltage (Key On, Engine Off) — expected: Approximately 5.0 Volts. Failure: Voltage that is significantly lower (e.g., below 4.5V) or higher (e.g., above 5.5V), or no voltage at all, indicates a short, open, or fault on the circuit.
• High-Pressure Fuel System Pressure — expected: Approx. 750 psi at idle to 2,250 psi at wide-open throttle.. Failure: While not a direct test for P0651, if the fuel pressure sensor is on the 'B' reference circuit, erratic fuel pressure readings could correlate with the voltage fault.

Scan Tool Commands That Help

• GDS2 (GM Global Diagnostic System 2): Active Test: Oil Pressure Solenoid Control — When P06DE is present with P0651, this command allows a technician to manually command the oil pressure control solenoid on and off. This helps determine if the solenoid is mechanically stuck or electrically unresponsive without having to remove it from the engine first.
• GDS2 (GM Global Diagnostic System 2): Circuit Test: Solenoid Resistance Check — This function within the GDS2 can guide the technician through testing the solenoid's coil resistance, often providing the expected range (typically 10-18 ohms) on-screen for immediate comparison.

Wiring & Ground Locations

• G103 — At the rear of the left-hand (driver's side) engine head.. This is a critical engine ground. A poor connection here can cause a variety of electrical issues and seemingly unrelated trouble codes, including reference voltage faults. A service bulletin mentions ensuring this connection is clean and tight when diagnosing electrical DTCs.
• G104 / G105 / G106 — Various ground points on the engine block and frame rail, often near the front of the engine.. These are primary engine and chassis grounds. A GM service bulletin regarding unrelated transmission codes emphasizes the importance of these grounds for overall module communication and electrical stability. A fault in these core grounds could manifest as a sensor reference voltage error.
• ECM/PCM Connectors — On the Engine Control Module (ECM), typically located in the engine bay.. The 5-volt reference signal originates from the ECM. Technicians must identify the correct pin for the 'Sensor Reference Voltage B' circuit at the ECM connector to test for proper voltage output directly at the source.

Real Owner Repair Stories

• Innova Garage YouTube Channel (Chevrolet Equinox (platform-mate with shared 2.5L LCV engine), 47,000 miles) — Check Engine Light with code P06DE.
  ❌ Tried (didn't work) Initially suspected a faulty oil pressure control solenoid valve located in the oil pan.
  ✅ What actually fixed it The vehicle was found to be extremely low on engine oil. After clearing the code and topping off the oil to the correct level, a test drive confirmed the code did not return. The root cause was either a slow oil leak or excessive oil consumption.

OEM Part Supersession History

• 12621234 → 12677836 (also listed as ACDelco 25202591) — Standard part evolution, likely for improved reliability or manufacturing process.
  Heads up: While physically similar, using an older or incorrect part number may lead to premature failure or incorrect pressure readings. It is critical to use the latest superseded part number for the vehicle's VIN.