C0131 on 2021-2022 Buick Encore: Brake Pressure Circuit Fault Guide

What's Unique About the 2021-2022 Buick ENCORE

On this generation of Buick Encore and its platform mates (like the Chevy Trax, Sonic, and Spark), the brake pressure sensor is not a separate, replaceable part. It is permanently integrated into the Brake Pressure Modulator Valve (BPMV), also known as the ABS module or hydraulic unit. This design means a failure of a small sensor requires replacing the entire expensive assembly. A specific GM Technical Service Bulletin (TSB), most recently PIC5704H, also warns technicians that this code can appear after a repair if shipping plugs are not removed from the new part before installation, which can cause a stuck 5-volt reading from the sensor and potentially damage the new module.

Diagnostic Flowchart

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

Symptoms You May Notice

• ABS warning light is on
• Traction Control System (TCS) or StabiliTrak warning light is on
• "Service StabiliTrak" or similar message on the driver information center (DIC)
• Cruise control may be inoperative

Most Likely Causes

1. Internal Failure of the Brake Pressure Sensor 🔴 High Probability The sensor is integrated into the Brake Pressure Modulator Valve (BPMV) and is a known failure point on this GM Gamma II platform, which includes the Encore, Trax, Sonic, and Spark.
   How to confirm: A professional scan tool (like a GM Tech 2 or GDS2) can read the live data from the brake pressure sensor. A normal reading is near 0V with the pedal released and should increase smoothly when pressed, staying within a range of approximately 0.12V to 3.2V. If the reading is stuck (often at 5 volts), erratic, or does not change with pedal application, the sensor has failed.
   Typical fix: Replace the entire Brake Pressure Modulator Valve (BPMV) assembly. The new module will require programming, a 'Brake Pressure Sensor Calibration', and a specialized 'Automated Bleed' procedure using a scan tool.
   Est. part cost: $350-$800
2. Shipping Plugs Not Removed After BPMV Replacement 🟡 Medium Probability This is a specific procedural error noted by GM in TSB #PIC5704H. New BPMV units are shipped with protective plugs that can be easily overlooked during installation, causing an immediate C0131 code with symptom byte 00. This mistake can also cause permanent damage to the new EBCM and BPMV.
   How to confirm: This cause should be suspected if the C0131 code appears immediately after a new BPMV has been installed, often with a live data reading stuck at 5 volts. The technician must remove the part to inspect the brake pressure sensor port for obstructions.
   Typical fix: Remove the BPMV assembly, inspect for and remove any shipping plugs or caps from the sensor port, and reinstall the unit. A full, scan-tool-actuated brake bleed procedure will be required again.
   Est. part cost: $0
3. Wiring or Connector Issue ⚪ Low Probability
   How to confirm: Visually inspect the wiring harness and connector at the EBCM/BPMV for damage, corrosion, chafing, or loose pins. Use a multimeter to test the sensor circuit for proper voltage (5V reference), ground, and signal continuity back to the EBCM. Check primary EBCM ground points, such as G110/G111 on the engine compartment firewall, for corrosion or looseness.
   Typical fix: Repair the damaged section of the wiring harness or clean/replace the connector. Clean and tighten affected ground points.
   Est. part cost: $10-$100

Rare But Worth Checking

• Faulty Electronic Brake Control Module (EBCM): While the pressure sensor is the most common point of failure within the assembly, the control module itself can fail, though it's less frequent. In some cases, a technician may mistakenly replace only the EBCM, which will not solve the problem if the sensor in the hydraulic unit is the cause.
• Brake Pressure Sensor Not Calibrated: After replacing the BPMV, a specific symptom code like C0131 5A, C0131 3A, or C0131 4B may set if the new sensor is not calibrated to the EBCM. This indicates a missed procedural step, not a faulty part. A GM-compatible scan tool is required to perform the 'Brake Pressure Sensor Calibration' function.

Diagnosis Steps

1. Verify the complaint and check for illuminated ABS and StabiliTrak warning lights.
2. Connect a professional-grade scan tool capable of reading GM chassis codes (C-codes).
3. Read the DTC and note any symptom bytes (e.g., 00, 5A, 3A, 4B). C0131 00 often relates to circuit malfunctions or the shipping plug issue, while C0131 5A can indicate a plausibility failure, and 3A/4B indicate a calibration issue.
4. Navigate to the EBCM live data and monitor the 'Brake Pressure Sensor' reading. The voltage should be near 0V with the pedal released and increase smoothly when the pedal is applied, staying within the 0.12V to 3.2V range.
5. If the reading is stuck (especially at 5V), absent, or erratic, a sensor/circuit fault is present.
6. If the code appeared immediately after a BPMV replacement, consult TSB #PIC5704H. The primary suspect is a shipping plug left in the new unit. The module must be removed for inspection.
7. If the original module is installed, inspect the wiring harness and connector at the BPMV for any visible damage, corrosion, or loose connections. Check for a stable 5V reference and good ground at the connector. Check the main EBCM ground point (e.g., G110/G111) for integrity.
8. If the wiring is confirmed to be good, the failure is internal to the BPMV assembly.
9. Replace the Brake Pressure Modulator Valve assembly.
10. After replacement, perform the 'Brake Pressure Sensor Calibration' and 'Automated Bleed' procedures using the scan tool to ensure proper function.

Parts You'll Likely Need

• Brake Pressure Modulator Valve (BPMV) (OEM #94559626) — This is the primary fix for code C0131, as it contains the non-serviceable brake pressure sensor that commonly fails. This part is also referred to as the ABS Control Unit.
  Trusted brands: ACDelco (GM Genuine)
  OEM price range: $350-$650
  Aftermarket price range: $350-$550

Technical Service Bulletins (TSBs) & Recalls

• PIC5704H: Diagnostic Tip - Traction and Stability Control Indicator on with Code C0131 Set After BPMV Replacement. Updated Feb. 2024, this TSB covers 2013-2022 Encore, Trax, Sonic, and Spark. It warns that if shipping materials are not removed from a new BPMV, code C0131 with symptom 00 will set, the brake pressure sensor will read a constant 5 volts, and the new module may be damaged.

Mechanic-Grade Diagnostic Values

• Brake Pressure Sensor Signal Voltage — expected: Approx. 0.12V to 3.2V. Should be near the low end with the pedal released and increase smoothly when pressed.. Failure: A signal voltage less than 0.12V or greater than 3.2V for more than one second. A reading stuck at a constant value (especially 5V) is a definitive failure indicator.

Hidden / Shadow Codes Worth Checking

• C0131 00: General 'ABS Pressure Circuit' failure. This is also the specific symptom byte that sets when shipping material is left on a new BPMV during installation. (see via GM GDS2 or equivalent professional scan tool.)
• C0131 3A: 'Incorrect Component Installed'. Sets after an EBCM has been replaced and the calibration to the brake pressure sensor is outside of the programmed range. (see via GM GDS2 or equivalent professional scan tool.)
• C0131 4B: 'Calibration Not Learned'. Sets when the mandatory 'Brake Pressure Sensor Calibration' procedure has not been performed after replacing the EBCM/BPMV. (see via GM GDS2 or equivalent professional scan tool.)
• C0131 5A: 'Pressure Circuit Plausibility Failure'. The EBCM detects a conflict, such as brake pressure increasing when it has not received a signal that the brake pedal is applied, or vice versa. (see via GM GDS2 or equivalent professional scan tool.)

Scan Tool Commands That Help

• GM GDS2 / Tech 2: Automated Bleed — This function is mandatory after replacing the BPMV or opening any hydraulic lines to the module. It cycles the internal ABS pump and valves to purge trapped air that cannot be removed by manual bleeding alone.
• GM GDS2 / Tech 2: Brake Pressure Sensor Calibration — This special function must be performed after replacing the EBCM or BPMV. It teaches the control module the 'zero' or baseline reading of the new sensor. Failure to perform this step is a common cause for an immediate C0131 code (specifically with symptom bytes 3A or 4B) on a new part.

Wiring & Ground Locations

• G110 / G111 — Located in the left center/rear of the engine compartment, often near the underhood fuse block or on the firewall.. This is a primary ground point for the Electronic Brake Control Module (EBCM) on this platform. A corroded or loose connection here can cause erratic voltage, leading to various EBCM codes including C0131.
• EBCM to BPMV Mating Surface — The physical connection where the black electronic module (EBCM) bolts onto the aluminum hydraulic block (BPMV).. A service manual notes that a C0131 code can be set if the EBCM is loosely attached to the hydraulic unit. The mounting bolts must be checked for proper torque.

Real Owner Repair Stories

• CorvetteForum user (Chevrolet Corvette C6 (different vehicle, but same GM code logic)) — C0131 code, Service ABS light, Active Handling turned off, no brake lights.
  ❌ Tried (didn't work) Clearing the code (it would return), Checking electrical connections at the ABS module
  ✅ What actually fixed it The root cause was a damaged Brake Pedal Position Sensor (BPPS) that was accidentally hit during an unrelated repair. Replacing the inexpensive BPPS and performing a calibration with a Tech 2 scan tool resolved the C0131 code and all symptoms.

OEM Part Supersession History

• 95189662, 95911078 → 94559626 — Standard part revision and consolidation by the manufacturer.