P0651 on 2015-2019 Chevrolet Colorado: Sensor Voltage 'B' Circuit Causes and Fixes

What's Unique About the 2015-2019 Chevrolet COLORADO

On the 2015-2019 Colorado, P0651 is specifically mentioned in GM Technical Service Bulletins (TSBs) alongside code P06DE, which relates to the engine oil pressure control system. This strong link suggests that the oil pressure control system is a common point of failure for the 'B' reference circuit. Unlike a generic P0651 fault, on the Colorado, your diagnosis should heavily prioritize this system. TSBs reveal the issue can be more severe than just a sensor; diagnostics for the accompanying P06DE code can lead to inspecting the oil pan for debris from broken internal piston oil squirters, a known mechanical failure point.

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 is on
• Reduced engine power or 'limp mode'
• Engine running rough, misfiring, or stalling
• Erratic gauge readings
• Hard starting
• Intermittent nature of the Check Engine Light (may clear on its own and return later)

Most Likely Causes

1. Wiring Harness Issue (Chafe, Open, or Short) 🔴 High Probability Engine vibration and heat can cause wiring insulation to wear down over time, especially where the harness is routed near engine components. A specific failure point noted in repairs is the harness getting pinched between the engine and transmission bellhousing, crushing the 5V reference wire.
   How to confirm: Visually inspect the wiring harness going to all sensors on the 'B' circuit, paying close attention to the oil pressure sensor/solenoid area and the harness routing near the transmission. Use a multimeter to check for continuity and shorts to ground or power on the reference wire.
   Typical fix: Repair the damaged section of the wire and protect it with loom or tape. In severe cases, a harness section or pigtail connector may need replacement.
   Est. part cost: $10-$50 for repair materials
2. Faulty Sensor on the 'B' Circuit 🟡 Medium Probability A sensor can fail internally and short out the 5-volt reference circuit. Given the TSBs, the oil pressure sensor is a primary suspect. Owners have reported that replacing the oil pressure sensor resolved the related P06DE code. The oil pressure control solenoid, which is part of the oil pump assembly, can also fail.
   How to confirm: Disconnect sensors on the 'B' circuit one by one. After disconnecting each sensor, clear the codes and check if P0651 returns. If the code disappears when a specific sensor is unplugged, that sensor is the likely culprit. For the oil pressure sensor, live data on a scan tool may show erratic readings.
   Typical fix: Replace the faulty sensor. For this vehicle, this is often the oil pressure sensor. 🎬 Watch: Step-by-step guide to replacing the Colorado oil pressure sensor. If the oil pressure control solenoid is at fault, the entire oil pump assembly typically requires replacement.
   Est. part cost: $30-$150 depending on the sensor
3. Corroded or Loose Electrical Connector ⚪ Low Probability Connectors exposed to moisture and road grime can develop corrosion, leading to poor electrical contact and voltage drops. The oil pressure sensor connector is located in an area susceptible to oil and dirt contamination.
   How to confirm: Unplug and inspect the connectors for the ECM and all related sensors. Look for green or white crust (corrosion) or bent/loose pins.
   Typical fix: Clean the connector pins with an electrical contact cleaner. If pins are damaged, the connector may need to be repinned or replaced.
   Est. part cost: $5-$30

Rare But Worth Checking

• Internal Engine Mechanical Failure: This is a rare but critical possibility specific to this platform when P0651 is paired with P06DE. TSB PIP5247A documents cases where internal components of a piston oil nozzle/squirter break apart and are found as debris in the oil pan, causing oil pressure issues that trigger the codes.
• Debris in Oil Pump Assembly: TSB PIP5676 notes that for a P06DE code, foreign material can get stuck in the oil pump's cold start checkball, affecting oil pressure regulation. If found, the debris can be cleaned out; if not, the oil pump assembly may need replacement.
• Faulty Engine Control Module (ECM): This is the least likely cause. The ECM's internal voltage regulator can fail, but all other possibilities should be exhausted before condemning the ECM.

Diagnosis Steps

1. Scan the vehicle for all stored trouble codes. Note any other codes that appear with P0651, especially P06DE.
2. Using a scan tool with live data, check the status of the 5-volt reference circuits. A healthy circuit should read between 4.8 and 5.2 volts.
3. Consult a vehicle-specific wiring diagram to identify all sensors powered by the 'B' reference circuit. On this truck, start with the oil pressure control system.
4. Visually inspect the entire wiring harness for the identified circuit. Look for any signs of chafing, melting, corrosion, or pinching, particularly near the engine, transmission housing, and exhaust.
5. If the visual inspection reveals nothing, begin disconnecting sensors on the circuit one at a time. After each one is disconnected, clear the codes and see if P0651 returns. If the code does not return after disconnecting a particular sensor, that sensor is likely shorted and is the cause of the problem.
6. If P06DE is present and oil pressure is low when hot, follow TSB PIP5247A guidance: if the oil pan is removed, inspect it for plastic or metal debris from broken piston oil nozzles/squirters.
7. Per TSB PIP5676, if P06DE persists, inspect the oil pump's cold start checkball for foreign material causing it to stick.
8. If all sensors are disconnected and the fault persists, test the reference wire itself for a short to ground or a short to voltage using a multimeter.
9. If the wiring, sensors, and related mechanical checks are all good, the final possibility is a fault within the Engine Control Module (ECM).

Parts You'll Likely Need

• Engine Oil Pressure Sensor (Switch) (OEM #ACDelco 12674782 (for 3.6L V6 LFX engine, verify by VIN)) — This sensor is a common failure point that can short the 5V reference circuit. It is relatively accessible and a frequent fix for the related P06DE code, as reported by owners.
  Trusted brands: ACDelco, Dorman, Autopart Premium
  OEM price range: $30-$60
  Aftermarket price range: $20-$40
• Engine Oil Pump Assembly — The oil pressure control solenoid that triggers P06DE is typically integrated into the oil pump/balance shaft module. If the solenoid itself fails, or if debris is found in the pump's checkball, the entire assembly often needs to be replaced. This is a labor-intensive job.
  Trusted brands: ACDelco, Melling
  OEM price range: $150-$300
  Aftermarket price range: $100-$220
• Wiring Harness Pigtail/Connector — If the fault is a corroded or damaged connector at a sensor, replacing the connector pigtail is often the most effective repair.
  Trusted brands: ACDelco, Dorman
  OEM price range: $30-$60
  Aftermarket price range: $15-$40

Related Codes That Often Appear With This One

• P06DE — This code for 'Engine Oil Pressure Control Solenoid Valve Stuck On' is directly linked to P0651 in GM's TSBs #PIP5247A and #PIP5676. The oil pressure control system is on the 5-volt reference 'B' circuit, so a fault with its wiring, sensor, or related mechanical components can trigger both codes.

Technical Service Bulletins (TSBs) & Recalls

• PIP5247A: Notes that P0651 may set with P06DE. Instructs technicians to follow diagnostics for P06DE, and if it leads to oil pan removal, to inspect for broken piston oil nozzle/squirter parts i

Platform-Specific Known Issues

• TSB #PIP5247A explicitly links P0651 with P06DE on these vehicles. It elevates the diagnosis beyond a simple electrical fault, instructing technicians to inspect for broken internal engine piston oil squirters if oil pressure is low, as debris can be found in the oil pan.
• TSB #PIP5676 provides another mechanical cause for the related P06DE code: foreign material getting lodged in the oil pump's cold start checkball, which requires inspection and potentially cleaning or replacement of the oil pump assembly.

Mechanic-Grade Diagnostic Values

• Sensor Reference Voltage 'B' Circuit — expected: 4.5 V to 5.5 V (typically 4.8 V to 5.2 V). Failure: Voltage reading outside the expected range (e.g., 0V or below 4.5V) indicates a short to ground or an open circuit.

Scan Tool Commands That Help

• GDS2 or equivalent professional scan tool: Active Test / Output Control — While not a specific command for P0651, a technician can use bidirectional controls to command components on other circuits. The primary diagnostic method for P0651 involves monitoring the 5V reference voltage while disconnecting sensors one-by-one to see when the voltage returns to normal.

Wiring & Ground Locations

• Harness Chafe Point — The wiring harness area where it passes between the engine block and the transmission bellhousing.. This area is a known chafe/crush point. If the harness is pinched during transmission service or from engine vibration, the 5V reference wire (often gray on GM vehicles) can short to ground, causing an intermittent or constant P0651.
• G101 (example) — Typically located on the engine block.. This is a primary ground for the Engine Control Module (ECM). A loose or corroded main ECM ground can cause a host of erratic electrical issues, including reference voltage faults. While not a direct cause of a single circuit fault, checking main grounds is a critical step in any electrical diagnosis.
• G103 (example) — Located on the cowl in the engine compartment, often near the brake booster.. This ground point serves multiple components, including the Body Control Module (BCM) and Data Link Connector (DLC). A fault here can cause widespread communication and electrical issues that could be confused with a P0651 fault.

Real Owner Repair Stories

• YouTube video 'P0651 code repair without a wiring diagram' (2007 Chevrolet Equinox (similar GM platform)) — Code P0651 - Reference Signal B Open.
  ❌ Tried (didn't work) Initial checks of various sensors.
  ✅ What actually fixed it The wiring harness was found crushed and pinched between the engine and transmission, likely from a previous transmission replacement. The gray 5V reference wire inside the harness was severed. The fix was to separate the engine and transmission slightly, pull the harness out, and repair the broken wire.
• YouTube channel 'South Main Auto Repair' (2013 Chevrolet Impala (similar GM platform)) — Code P0651, intermittent loss of 5V reference voltage.
  ❌ Tried (didn't work) Unplugging individual sensors on the circuit did not consistently isolate the fault.
  ✅ What actually fixed it The mechanic found the fault by wiggling the wiring harness near the transmission. The 5V signal would drop to 0V when the harness was pushed against a transmission bracket. The harness had rubbed through on the sharp edge of the bracket, causing an intermittent short to ground. The fix was to repair the damaged wire and re-route the harness away from the sharp edge.

OEM Part Supersession History

• 12570798, 12621649, 12621659 → 12674782 — Standard part consolidation and design updates by the manufacturer.

Model Year Variations Within This Range

• 2015-2016: These model years are equipped with the 3.6L LFX V6 engine. Diagnostics for the related P06DE code will focus on this engine's specific oil pressure system.
• 2017-2019: These model years use the updated 3.6L LGZ V6 engine. This engine features a more complex two-stage variable displacement oil pump and Active Fuel Management (AFM). Therefore, diagnosis of the associated P06DE code is different and must account for the two-stage pump's operation and potential AFM system-related faults.