P0558 on 2017-2021 GMC Acadia: Brake Booster Pressure Sensor Circuit High Fixes

What's Unique About the 2017-2021 Gmc ACADIA

On this generation of the GMC Acadia and its platform mates (like the Cadillac XT5, Chevrolet Traverse, and Buick Enclave), the P0558 code is a known issue addressed by a specific Technical Service Bulletin, #20-NA-071. The bulletin points to potential electromagnetic interference (EMI) in the engine harness and poor terminal tension at the sensor connector as root causes, rather than just a simple sensor failure. This makes checking the wiring and referencing the TSB a critical first step that is unique to this platform, as the official fix involves installing a new, separate wiring harness and replacing the vacuum hose/sensor assembly.

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
• "Service Power Brake Assist" message on the driver information center (DIC)
• Hard brake pedal requiring more effort to press
• Increased stopping distance
• ABS or Stabilitrak/Traction Control warning lights may also illuminate
• Hissing sound from the brake booster area
• Engine may stall when braking

Most Likely Causes

1. Faulty Brake Booster Pressure Sensor Wiring/Connector 🔴 High Probability GM Technical Service Bulletin #20-NA-071 explicitly identifies poor terminal tension and potential for EMI in the engine harness as the primary cause for this code on these vehicles. The original wiring is susceptible to interference that can corrupt the sensor's signal.
   How to confirm: Inspect the sensor connector for corrosion or loose pins. The definitive confirmation is following the diagnostic procedure in TSB #20-NA-071, as this is the most common failure mode.
   Typical fix: Install the updated external wiring harness as described in TSB #20-NA-071. This involves cutting the old connector, taping off the old wires, and splicing in the new harness which is routed away from sources of EMI. The TSB also calls for replacing the power brake booster vacuum hose.
   Est. part cost: $50-$100 for the harness kit and hose
2. Failed Brake Booster Pressure Sensor 🟡 Medium Probability The sensor itself can fail internally, causing it to send a constant high voltage signal. While the TSB points to wiring first, the sensor is often replaced concurrently as part of the official repair procedure, as it is integrated into the vacuum hose assembly.
   How to confirm: With a scan tool, observe the live data for the brake booster pressure sensor. If the voltage is stuck high (near 5 volts) and does not change with vacuum applied, and the wiring is confirmed to be good, the sensor is faulty.
   Typical fix: Replace the brake booster pressure sensor. On these Acadia models, the sensor is part of the power brake booster vacuum hose assembly which must be replaced as a unit.
   Est. part cost: $70-$120 for the hose and sensor assembly
3. Faulty Powertrain Control Module (PCM) ⚪ Low Probability
   How to confirm: This should only be considered after all other possibilities (sensor, wiring, connections) have been exhaustively ruled out by a professional technician. This is a rare cause for this specific code.
   Typical fix: Replace and reprogram the PCM. This requires specialized tools and access to manufacturer software.
   Est. part cost: $500-$800

Diagnosis Steps

1. Verify the code P0558 is present using an OBD-II scanner.
2. Check for the 'Service Power Brake Assist' message on the dashboard.
3. Obtain a copy of GM Technical Service Bulletin #20-NA-071, as it contains the most likely cause and specific repair procedure for this exact vehicle and issue.
4. Visually inspect the brake booster pressure sensor and its electrical connector for any signs of damage, corrosion, or looseness.
5. Follow the TSB procedure to replace the power brake booster vacuum hose and install the new external wiring harness. This is the official GM-recommended fix. The procedure involves locating the original connector, cutting the wires, taping them off, and then routing and connecting the new harness to the ECM.
6. If the TSB procedure does not resolve the issue, test the sensor's signal wire for a short to voltage using a multimeter.
7. Using a scan tool, monitor the sensor's voltage reading in real-time. A reading that is stuck high (typically near 5 volts) points towards a sensor or circuit fault.
8. If wiring and connections are confirmed good and the TSB has been performed, suspect a faulty sensor. Replace the brake booster pressure sensor (which is integrated with the vacuum hose).
9. Clear the codes and test drive the vehicle to ensure the repair was successful.

Parts You'll Likely Need

• Power Brake Booster Vacuum Sensor Wiring Harness (OEM #84773558) — As per TSB #20-NA-071, a faulty harness or poor connection is the most likely cause of this code on the 2017-2021 Acadia. This is the specific part called for in the bulletin.
  Trusted brands: ACDelco, GM Genuine Parts
  OEM price range: $50-$100
  Aftermarket price range: $40-$80
• Power Brake Booster Vacuum Hose with Sensor (OEM #23465287) — The TSB also requires the replacement of the vacuum hose, which includes the sensor. This part number is referenced in a related TSB (#21-NA-045) for vacuum pipe issues. Even if the sensor hasn't failed, it is replaced as part of the official repair procedure.
  Trusted brands: ACDelco, GM Genuine Parts
  OEM price range: $70-$120
  Aftermarket price range: $40-$90

Related Codes That Often Appear With This One

• P0557 — P0557 is for 'Brake Booster Pressure Sensor Circuit Low'. Both codes are mentioned in the same TSB (#20-NA-071) and can be caused by the same wiring issues, indicating an intermittent or erratic connection.
• P050F — P050F indicates 'Brake Assist Vacuum Too Low'. This can be a related code as the system may detect a performance issue in addition to the circuit fault. TSB #21-NA-045 also lists this code alongside P0558 for related vacuum pipe issues.

Technical Service Bulletins (TSBs) & Recalls

• 20-NA-071: Addresses a Service Engine Soon Lamp and/or Service Power Brake Assist message with DTCs P0557 or P0558 stored, caused by wiring issues (EMI and poor terminal tension). This is the primary document for this issue.
• 21-NA-045: Addresses multiple brake booster DTCs including P0558, caused by the routing of the power brake booster vacuum pipe. Recommends replacing the pipe and a related connector.

Platform-Specific Known Issues

• TSB 20-NA-071 was issued by GM for this exact code (along with P0557) on 2017-2021 Acadias. It points to EMI and poor terminal tension in the sensor's wiring harness and provides a specific repair procedure involving a new external harness and vacuum hose replacement.
• TSB 21-NA-045 also mentions P0558 and other brake booster codes, pointing to issues with the routing of the power brake booster vacuum pipe, further highlighting the sensitivity of this system on these vehicles.

Mechanic-Grade Diagnostic Values

• Brake Booster Pressure Sensor Signal Voltage — expected: The sensor operates on a 5V reference circuit. Voltage should vary with brake application and engine vacuum. A normally functioning sensor will show a voltage change when the brake pedal is pressed.. Failure: The ECM will set code P0558 if the sensor output voltage is 4.8 V or more 🎬 Watch: Understanding the P0558 circuit high code and sensor data. for 2 seconds. This indicates a short to voltage or an internal sensor failure.
• Sensor Circuit Test at ECM Connector — expected: With the sensor disconnected, check for 5V reference and a good ground at the harness connector. Test for continuity on the signal wire back to the ECM. Resistance should be less than 1 ohm.. Failure: Absence of 5V reference or ground, or high resistance/open on the signal wire points to a wiring fault between the sensor and the ECM.

Scan Tool Commands That Help

• GDS2 / Tech2 / Professional Scan Tool: Live Data / Data Display for Brake Booster Pressure Sensor — This is the primary diagnostic method. Monitor the sensor's voltage or pressure reading in real-time while applying and releasing the brake pedal with the engine running. A stuck high voltage (near 5V) that does not change confirms a fault in the sensor or its circuit.

Wiring & Ground Locations

• B19B Brake Booster Vacuum Sensor — Mounted on the power brake booster vacuum hose assembly in the engine compartment.. This is the sensor that provides the signal to the ECM. TSB #20-NA-071 identifies poor terminal tension at this sensor's connector as a primary cause of the code.
• ECM Connector X1 (V6 Engines - LGX/LFY) — At the Engine Control Module (ECM).. TSB #20-NA-071 requires re-pinning this connector. Pin 65 (YE/VT wire, Circuit 6030) is the 5V reference. Pin 45 (YE/RD wire, Circuit 6031) is the signal. Pin 44 (BK/WH wire, Circuit 2151) is the low reference/ground.
• ECM Connectors X1 & X3 (4-Cyl Engine - LCV) — At the Engine Control Module (ECM).. TSB #20-NA-071 specifies different pin locations for the 4-cylinder engine. Pin 32 (X1, YE/VT wire, Circuit 6030) is 5V reference. Pin 15 (X3, YE/RD wire, Circuit 6031) is the signal. Pin 20 (X3, BK/WH wire, Circuit 2151) is the low reference/ground.
• Circuit 2151 (formerly 6032) — This is the ground/low reference circuit for the sensor, running from the sensor to the ECM.. The TSB procedure involves cutting the original ground wire and splicing it into the new harness near the ECM connector. The TSB was revised to change this circuit number from 6032 (BK/YE) to 2151 (BK/WH), a critical detail for technicians.

Real Owner Repair Stories

• acadiaforum.net user discussion (2018 GMC Acadia) — Check Engine Light on and 'Service Brake Assist' message displayed on the DIC.
  ❌ Tried (didn't work) Initial diagnosis pointed to the sensor, but simply replacing the sensor is a common misdiagnosis that may not permanently fix the issue.
  ✅ What actually fixed it The issue was resolved by performing the repair outlined in GM TSB #20-NA-071, which involves replacing the power brake booster vacuum hose/sensor assembly AND installing the new, separate wiring harness (P/N 84773558) to shield it from EMI.

OEM Part Supersession History

• 13577043, 13580878, 19356496, 88988939 → 84773558 — These are previous part numbers for wiring harness connectors or pigtails that have been superseded by the harness kit specified in TSB 20-NA-071.
  Heads up: Using an older pigtail part number instead of the full harness kit (84773558) will not resolve the root cause of the issue (EMI interference) and the P0558 code is likely to return.

Model Year Variations Within This Range

• 2017-2021: The ECM pin locations for the brake booster pressure sensor circuit are different depending on the engine. V6 models (LGX/LFY) use pins 44, 45, and 65 in the X1 connector. 4-cylinder models (LCV) use pin 32 in X1 and pins 15 and 20 in the X3 connector. This is critical information when performing the TSB #20-NA-071 wiring repair.