U0672 on 2020-2024 Cadillac XT5: Coolant Pump Communication Loss Causes and Fixes

What's Unique About the 2020-2024 Cadillac XT5

The Cadillac XT5 from this period, specifically with the 2.0L LSY turbo engine, uses an advanced Active Thermal Management system. 🎬 Watch: A deep dive into the 2.0L LSY engine's cooling defects. This system relies on an electric, variable-speed water pump instead of a simple belt-driven one. While efficient, this introduces a new point of failure: the electrical communication link. General Motors has acknowledged this issue through multiple Technical Service Bulletins (TSBs), which point directly to the pump's electrical connector as a common source of the problem. The prevalence of this specific connection issue prompted GM to create a unique labor operation (4088838) for billing 0.3 hours of warranty time just to inspect and cycle the connector, indicating how frequently this is the sole cause of the fault.

Diagnostic Flowchart

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

Generation note: The 2020-2024 model year range covers the first-generation Cadillac XT5, which received a significant refresh in 2020 that included the introduction of the 2.0L LSY turbocharged engine. A second generation was unveiled for other markets in late 2024. This guide applies to the first-generation models from 2020 onward, particularly those with the 2.0L engine specified in the TSBs.

Symptoms You May Notice

• Check Engine Light (Malfunction Indicator Lamp or MIL) is on.
• Engine overheating or temperature gauge reading high.
• Message on the driver information center (DIC) about reduced engine power.
• Loss of cabin heat, as hot coolant isn't being circulated to the heater core.
• Radiator fan running at high speed constantly, even when the engine is not hot.
• Coolant leaks, appearing as orange or pink fluid (Dex-Cool) under the front of the vehicle.

Most Likely Causes

1. Poor Electrical Connection at Coolant Pump 🔴 High Probability This is a widely known issue documented by GM in TSBs #PIP5863B and #PIP5863C. The 4-pin connector can suffer from contamination, poor terminal tension (fretting), corrosion from moisture, or improperly seated pins, interrupting the LIN bus communication.
   How to confirm: Visually inspect the electric coolant pump's wiring harness connector (X327) for any signs of damage, corrosion, or loose pins. Unplug the connector, check for issues like water intrusion or backed-out terminals, and plug it back in securely ('cycle the connection'). Clearing the code after cycling the connection will often resolve the issue if this was the cause.
   Typical fix: Clean the connector terminals with an appropriate electrical contact cleaner and apply dielectric grease to prevent future moisture intrusion. If the connector or terminals are damaged, the connector pigtail will need to be replaced. Often, simply cycling the connection and clearing the code resolves the issue.
   Est. part cost: $0-$35
2. Failed Electric Engine Coolant Pump 🟡 Medium Probability The pump contains an integrated control module. If this internal module fails electronically, it cannot communicate with the ECM, triggering the U0672 code. The pump can also fail mechanically (leaks, bearing noise), though this may not always set a U-code initially.
   How to confirm: If the wiring and connector are confirmed to be in good condition and the code returns immediately after being cleared, the pump module is the likely culprit. A professional scan tool can attempt to directly communicate with the pump module to confirm it's unresponsive.
   Typical fix: Replace the entire electric engine coolant pump assembly. It is a single unit with the control module built-in. No programming is required after installation.
   Est. part cost: $180-$650
3. Chafed Wiring Harness ⚪ Low Probability Another GM TSB (#23-NA-074) notes that on some XT5, XT6, Blazer, and Acadia models, the main engine wiring harness can chafe on a sharp edge of the battery tray support bracket. This can cause a short in various circuits, including the communication line for the coolant pump, triggering U0672 among many other possible codes.
   How to confirm: With the battery removed, carefully inspect the wiring harness in the area around and under the battery tray for any signs of rubbing, exposed copper wires, or damage.
   Typical fix: Repair the damaged wires according to service procedures. The TSB recommends cutting 3-inch strips of anti-abrasion deadener tape and wrapping them around the sharp metal edges of the battery tray bracket to prevent future chafing.

Rare But Worth Checking

• Internal Pump Circuit Board Defect:

Diagnosis Steps

1. Scan the vehicle for codes. Confirm that U0672 is present, either active or in history.
2. Follow GM TSB #PIP5863C: Locate the electric engine coolant pump on the lower side of the engine.
3. Carefully inspect the wiring harness and the 4-pin electrical connector (X327) leading to the pump. Look for contamination, corrosion, backed-out pins, or any visible damage.
4. Disconnect the connector, inspect the terminals inside, and reconnect it firmly. This is known as 'cycling the connection'.
5. Clear the U0672 trouble code with a scan tool.
6. Start the engine and let it run to see if the code returns. If it does not, the issue was likely a poor connection. Applying dielectric grease is recommended.
7. If the code returns, inspect for a chafed harness near the battery tray per TSB 23-NA-074.
8. If the harness is intact, the next step is to test the wiring between the ECM and the pump for continuity and shorts.
9. If the wiring is confirmed to be good, the electric engine coolant pump assembly has likely failed and needs to be replaced.

Parts You'll Likely Need

• Electric Engine Coolant Pump Module (OEM #12738953) — This is the most common part to fail if the electrical connector is not the source of the problem. The control module is integrated into the pump, so the entire assembly must be replaced. This part number supersedes older versions including 12724522, 55506790, 55508939, 55510113, and 55515497.
  Trusted brands: ACDelco, GM Genuine Parts
  OEM price range: $180-$350
  Aftermarket price range: $150-$250

Related Codes That Often Appear With This One

• P26BB — This code relates to the separate 'Coolant Flow Control Valve' that works with the electric pump. A communication failure with the pump (U0672) can cause related faults in the system. TSB 21-NA-256 addresses P26BB on LSY engines, noting it can sometimes occur during a break-in period on new vehicles.

Technical Service Bulletins (TSBs) & Recalls

• PIP5863C: Malfunction Indicator Lamp (MIL) Illuminated due to a U0672 setting. Advises the technician to perform Electric Engine Coolant Pump connection inspections.
• PIP5863B: An earlier version of the same bulletin, also advising to check the pump connection for the U0672 code.
• 23-NA-074: Addresses multiple communication DTCs, including U0672, that can be caused by the engine wiring harness chafing on the battery tray support bracket.

Platform-Specific Known Issues

• GM has issued Technical Service Bulletin PIP5863C, which directly addresses the U0672 code on 2020-2024 Cadillac XT5 models. It explicitly advises technicians to inspect the Electric Engine Coolant Pump connection first before replacing parts.
• TSB 23-NA-074 identifies a harness chafing point under the battery tray as a possible cause for U0672 and a host of other communication codes on the XT5 and its platform mates.

Mechanic-Grade Diagnostic Values

• LIN Bus Voltage (communicating) — expected: Toggling between approximately 1V (low) and 11-12V (high).. Failure: A steady, non-toggling voltage (e.g., stuck at 12V or 0V) indicates a communication fault.
• Power Supply at Pump Connector (Pin 4, RD/YE wire) — expected: Battery Voltage (12V+) with key on.. Failure: No or low voltage points to a blown fuse or a break in the power supply wire.
• Ground Resistance at Pump Connector (Pin 1, BK wire) — expected: Below 0.1 Ω to a known good chassis ground.. Failure: Resistance higher than 0.1 Ω indicates a poor ground connection, which can cause communication errors.

Scan Tool Commands That Help

• GDS2 (GM Global Diagnostic System 2): Engine > Output Controls > Low Temperature Loop Coolant Pump — This bidirectional command allows a technician to manually activate the electric coolant pump at various speeds (e.g., 10-100%). It is used to verify if the pump motor runs when commanded, which helps differentiate a wiring/communication issue from a physically failed pump.

Wiring & Ground Locations

• X327 — The 4-pin electrical connector directly on the electric engine coolant pump, located on the lower driver's side of the engine block.. This is the primary point of failure cited in GM TSBs. Poor connection, corrosion, or backed-out pins at this connector will directly cause a U0672 code. The pins are: Pin 1 (BK) - Ground, Pin 2 (GY) - LIN Data Bus, Pin 4 (RD/YE) - Fused Battery Positive Voltage.
• G101 — Located at the front of the engine on the lower block.. This is a primary engine ground point that provides the ground reference for the Engine Control Module (ECM). A poor connection here can cause a wide range of communication codes, including U0672, as the ECM may not be able to communicate reliably with other modules.

Real Owner Repair Stories

• YouTube user 'PAULY'S AUTO' (GM Truck with 2.7L L3B Engine (shares Active Thermal Management architecture with LSY)) — Check Engine Light with U0672 and other LIN bus fault codes.
  ❌ Tried (didn't work) Initial visual inspection did not reveal the fault.
  ✅ What actually fixed it A massive voltage drop (5-7 volts) was measured from the battery-top fuse block when the fuse was wiggled. The fuse block had an internal failure and required replacement to restore proper voltage to the pump circuit.
• YouTube user 'Casi que motor' (2022 Chevrolet Silverado 1500 2.7L) — Check Engine Light with code U0672.
  ✅ What actually fixed it The electric water pump had an internal short to ground. Replacing the water pump and the 80-amp fuse on the battery fuse block (which had blown due to the short) resolved the issue.

OEM Part Supersession History

• 55506790, 55508939, 55510113, 55515497, 12724522 → 12738953 — Standard part evolution for improved reliability and manufacturing consistency. The history of electronic failures (per program N202320510) suggests revisions were made to improve circuit board and internal module durability.