C1173 on 2025 Buick Enclave: TPMS Relearn Failure Causes and Fixes

What's Unique About the 2025-2025 Buick ENCLAVE

The 2025 Buick Enclave, along with its GM platform mates like the 2024-2025 GMC Acadia and Chevrolet Traverse, utilizes a newer vehicle architecture where TPMS functions are linked with other modules, like the OnStar (Telematics Control Protocol or TCP) module, via an Ethernet connection. A grounding issue with this specific Ethernet cable can cause interference, leading to the C1173 code. This is a specific design-related fault, making it different from older vehicles where a TPMS code almost always pointed to a bad sensor in the wheel.

Diagnostic Flowchart

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

Symptoms You May Notice

• TPMS warning light is illuminated on the dashboard.
• A 'Service Tire Monitor System' message appears in the driver information center.
• The vehicle is unable to complete the TPMS relearn procedure, especially for the front tires.
• Tire pressure readings may be missing or incorrect on the display, often showing as dashes (--).

Most Likely Causes

1. Ethernet Communication Interference 🔴 High Probability As documented in GM TSB #24-NA-166, the Ethernet cable for the OnStar (TCP) module can have an intermittent grounding issue at the X7 connector, causing interference that disrupts TPMS relearn procedures.
   How to confirm: A GM technician will follow the TSB's diagnostic steps. The key step is to lower the rear headliner to access and disconnect the X7 Ethernet connector at the Telematic Control Module. If the TPMS relearn procedure then succeeds with the module disconnected, the TSB applies and the overlay harness is the confirmed fix.
   Typical fix: Install the specified Ethernet cable overlay harness (GM Part #26501515). The procedure involves routing the new harness and cutting off both ends of the original, faulty Ethernet cable to ensure it is not used in future repairs.
   Est. part cost: $50-$100 for the overlay harness (part only).

Rare But Worth Checking

• Faulty TPMS Sensor: → Shop Tire Pressure Monitoring System (TPMS) Sensor While the TSB is the most likely cause, an individual TPMS sensor can still fail due to a dead battery (lifespan is typically 5-10 years) or physical damage. If the TSB diagnostics do not identify a communication issue, the sensor itself should be tested.
• Faulty Body Control Module (BCM) or Remote Control Door Lock Receiver (RCDLR): The module responsible for receiving the TPMS signals could be faulty. This is rare and should only be considered after ruling out the TSB and individual sensors.

Diagnosis Steps

1. Verify code C1173 and any other related codes (C1171, C1172, C1174) with a professional scan tool that can read GM chassis codes.
2. Check the vehicle's VIN for applicability of GM Technical Service Bulletin #24-NA-166.
3. Attempt a standard TPMS relearn procedure. 🎬 Watch: How to perform a standard TPMS relearn on GM vehicles. If it fails, this strongly points towards the TSB issue rather than a simple sensor fault.
4. Follow the specific diagnostic procedure outlined in TSB #24-NA-166. This involves accessing the Telematic Control Module (OnStar module) by lowering the rear headliner, disconnecting the X7 Ethernet connector, and attempting the relearn again.
5. If the relearn succeeds with the connector unplugged, the TSB fault is confirmed. Install the specified Ethernet cable overlay harness, GM Part #26501515.
6. If the TSB does not apply or resolve the issue, proceed with standard diagnostics for the individual TPMS sensors using a TPMS tool to check for battery life and signal output.

Parts You'll Likely Need

• Cable, Body Wiring Harness Modular Pair (Ethernet Overlay) (OEM #26501515) — This is the specific part designed by GM to fix the known communication and grounding issue that causes code C1173, as detailed in TSB #24-NA-166.
  Trusted brands: GM Genuine Parts
  OEM price range: $50-$100
• Tire Pressure Monitoring System (TPMS) Sensor — This part would only be needed if the primary cause (the TSB wiring issue) is ruled out and a specific sensor is found to be faulty.
  Trusted brands: ACDelco, Schrader, Continental
  OEM price range: $60-$120
  Aftermarket price range: $30-$70

Related Codes That Often Appear With This One

• C1171 — This code is part of the same family and is mentioned in TSB #24-NA-166, indicating a system-wide TPMS relearn failure.
• C1172 — This code is part of the same family and is mentioned in TSB #24-NA-166, indicating a system-wide TPMS relearn failure.
• C1174 — This code is part of the same family and is mentioned in TSB #24-NA-166, indicating a system-wide TPMS relearn failure.

Technical Service Bulletins (TSBs) & Recalls

• 24-NA-166: DTC C1171 C1172 C1173 C1174 Tire Pressure Monitor Sensor Unable to Relearn Ethernet Cable Overlay for TCP OnStar Module. (This bulletin supersedes a previous preliminary version, PIT6188E).

Platform-Specific Known Issues

• A known issue documented in GM TSB #24-NA-166 describes how interference from the OnStar module, due to an Ethernet cable grounding problem, can prevent the TPMS from completing a relearn procedure and set codes C1171, C1172, C1173, and/or C1174.
• As these are new generation vehicles for the 2024-2025 model years, some electronic issues are being discovered and addressed via TSBs. This TPMS fault is one of the more widely documented early issues for this platform.

Mechanic-Grade Diagnostic Values

• GM Data Bus Activity (General) — expected: A toggling voltage signal, indicating data transfer. For older Class 2 networks, this was 0V to 7V. The principle is the same for newer CAN/Ethernet buses.. Failure: A bus that is 'stuck' at a constant voltage (either high or low) indicates a short or a faulty module pulling the network down.

Scan Tool Commands That Help

• GDS2 (GM Diagnostic Software): TPMS Relearn Procedure — This is the primary function that fails, triggering code C1173. It is initiated to test if the system can learn sensor positions. The TSB diagnostic procedure requires attempting this function before and after disconnecting the OnStar module.
• GDS2 (GM Diagnostic Software): Module Communication Status / Data Bus Diagnostic Tool — Used to 'ping' all modules on the network to verify which ones are communicating. In a complex network fault, this can help identify a module that is offline, although for the C1173 issue, the OnStar module may still appear to be communicating intermittently.
• Techline Connect (TLC) / SPS2: Module Programming — This tool is used for programming or reprogramming modules like the BCM or ECM. While not a direct fix for C1173, it would be used if a module itself were replaced or if a software update was released to address a related anomaly.

Wiring & Ground Locations

• Telematics Control Protocol (TCP) Module — In the passenger compartment, accessed by lowering the rear of the headliner. Forum posts for similar GM models suggest it is at the rear shelf, under the trim.. This is the OnStar module. The faulty Ethernet communication that causes C1173 originates from the wiring connected to this module.
• Connector X7 — The specific Ethernet connector at the Telematics Control Protocol (TCP) Module.. This is the connector that TSB #24-NA-166 instructs technicians to disconnect to confirm the diagnosis. If the TPMS relearn works after unplugging X7, the TSB repair is the correct path.
• Overlay Harness Routing Path — The new harness (PN 26501515) is routed from the TCP module at the rear headliner, down the right-hand C-pillar, along the floor under the right-hand rear and front door sill plates.. This is the physical path of the official repair, bypassing the original faulty Ethernet cable.

Real Owner Repair Stories

• OnStar Community Forum User (2025 Buick Enclave) — Complete failure of the OnStar/Telematics module. The user notes it's a known issue and it took over a week just to get a service appointment.
  ❌ Tried (didn't work) Waiting for the system to self-correct.
  ✅ What actually fixed it The issue was identified by the dealer as a failed Telematics module, which is the same component implicated in TSB 24-NA-166. The owner was informed the part was on backorder, which is a common complaint for this issue on new GM SUVs. The ultimate fix is the dealer performing the TSB or replacing the module when parts become available.

OEM Part Supersession History

• N/A → 26501515 — This is a newly created part specifically for the repair outlined in TSB 24-NA-166. It does not supersede a previous version of the overlay harness.