U0672 on 2019-2024 Cadillac XT4: Electric Coolant Pump Communication Failure Causes and Fixes

What's Unique About the 2019-2024 Cadillac XT4

The Cadillac XT4 with the 2.0L LSY engine uses a modern, electronically controlled water pump as part of its Active Thermal Management system instead of a traditional belt-driven pump. This design allows for more precise temperature control but introduces a potential point of failure in the communication network. General Motors has acknowledged intermittent connection issues by issuing multiple Technical Service Bulletins (TSBs), such as PIP5863C, that specifically address code U0672 on this platform and many others sharing the same engine. These bulletins point technicians to check the pump's electrical connector first before attempting any component replacement.

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 (Malfunction Indicator Lamp) is on.
• Engine overheating or temperature gauge rising rapidly into the red zone.
• Message on the driver information center regarding engine temperature, such as 'Engine Overheated', or a reduced power warning.
• Loss of cabin heat, as hot coolant may not be circulating to the heater core.
• Engine may enter a reduced power or 'limp' mode to protect itself from overheating damage.
• Cooling fans running at maximum speed as a fail-safe measure.

Most Likely Causes

1. Poor Electrical Connection at the Coolant Pump 🔴 High Probability GM has issued multiple TSBs (PIP5863B, PIP5863C) specifically for this issue, indicating it's a known problem across numerous models with the LSY engine. The bulletins state the cause is a 'Potential Electric Engine Coolant Pump Connection Issue' and advise checking for contamination, poor terminal tension, or corrosion at the 4-pin connector.
   How to confirm: Visually inspect the wiring harness and 4-pin connector at the electric engine coolant pump for any signs of damage, looseness, or corrosion. Unplug the connector, check the pins, and plug it back in securely (a process called 'cycling the connector'). Clear the code and see if it returns. TSB PIP5863B allocates 0.3 hours of labor time for this specific inspection.
   Typical fix: Clean the connector terminals with electrical contact cleaner and apply dielectric grease to prevent future moisture intrusion. If the connector or wiring is damaged, it will need to be repaired or replaced. In many documented cases, simply cycling the connector resolves the intermittent fault.
   Est. part cost: $0-$25
2. Failed Electric Engine Coolant Pump 🟡 Medium Probability The pump contains an integrated control module. An internal failure of this electronic module will prevent it from communicating with the ECM, triggering the U0672 code. GM has a history of electronic faults with this pump design, including a prior customer satisfaction program (N202320510) for a similar issue on other models.
   How to confirm: If the wiring and connector are confirmed to be good and the code still returns immediately after being cleared, the pump assembly itself is the likely culprit. A professional scan tool can be used to directly query the pump module; a lack of response confirms the failure.
   Typical fix: Replace the entire electric engine coolant pump assembly. This is a labor-intensive job that involves draining the cooling system.
   Est. part cost: $180-$740
3. Wiring Harness Chafe/Damage ⚪ Low Probability Another TSB (23-NA-074) notes that wiring harnesses in the engine bay, particularly near the battery tray, can chafe against brackets, causing shorts or open circuits for various components, including those on the communication network. This can interrupt the LIN bus signal to the coolant pump.
   How to confirm: Perform a detailed visual inspection of the engine wiring harness, especially in areas where it contacts brackets or other components. Check for continuity and shorts on the communication (LIN bus) and power/ground wires going to the coolant pump using a multimeter.
   Typical fix: Repair the damaged section of wire and protect the harness from future chafing using loom or anti-abrasion tape.
   Est. part cost: $5-$50

Rare But Worth Checking

• Failed Engine Control Module (ECM): This is very rare. The ECM is a robust component. All other possibilities, especially wiring and the pump itself, should be exhaustively ruled out before considering ECM replacement.

Diagnosis Steps

1. Read the trouble codes with an OBD-II scanner to confirm U0672 is present.
2. Turn the vehicle off. Locate the electric engine coolant pump on the lower part of the engine.
3. Carefully inspect the 4-pin electrical connector and wiring harness leading to the pump. Look for any signs of corrosion, damage, or loose connections.
4. As per TSB PIP5863C, unplug the connector, inspect the pins for damage or contamination, and securely plug it back in. This is known as 'cycling the connector'. This step alone often resolves the issue.
5. Clear the U0672 trouble code using the scanner.
6. Start the engine and let it run to see if the Check Engine Light and code return. If they do not, the issue was likely the intermittent connection, and you should advise the customer that GM is aware of the issue.
7. If the code returns immediately, the next step is to test the circuit. Using a multimeter and a wiring diagram, check for proper power, ground, and communication signal at the pump connector.
8. If the wiring and signals are correct, the fault is internal to the electric engine coolant pump. The pump assembly will need to be replaced.
9. If the pump is replaced, the cooling system must be drained, refilled with DEX-COOL coolant, and properly bled of air to prevent air pockets.

Parts You'll Likely Need

• Electric Engine Coolant Pump (OEM #12738953) — This is the most common part to fail if the issue is not a simple connection problem. The integrated control module fails, cutting off communication with the ECM. This part number is the latest revision and supersedes several older numbers including 12724522, 55506790, 55508939, 55510113, and 55515497.
  Trusted brands: ACDelco, GM Genuine
  OEM price range: $627-$739
  Aftermarket price range: $180-$250

Related Codes That Often Appear With This One

• P26BB — This code relates to the 'Engine Coolant Control Valve', which works in conjunction with the electric pump as part of the Active Thermal Management system. A fault in the system can trigger codes for related components.
• U1348 — This code can appear alongside U0672 and also points to a communication issue on the same data bus line (LIN Bus) that the coolant pump uses. A Reddit user with a 2022 Chevy Blazer reported both codes appearing simultaneously.

Technical Service Bulletins (TSBs) & Recalls

• PIP5863C: Advises technicians to inspect the Electric Engine Coolant Pump connection and cycle it to resolve a U0672 code.
• PIP5863B: An earlier version of the same bulletin, also pointing to the pump connection as the likely cause for U0672. It covers a wide range of GM vehicles with the 2.0L LSY and 2.7L L3B engines.
• 23-NA-074: While not specific to U0672, it notes potential for various electrical codes due to wire chafing on the battery tray support bracket, which could be a root cause.

Platform-Specific Known Issues

• A known issue with the electrical connector at the pump can cause an intermittent U0672 code. GM's official procedure is to first inspect and cycle the connector before replacing any parts.
• TSB PIP5863B/C specifically notes that if cycling the connector resolves the code, the vehicle should be returned to the customer with the advice that GM is aware of the intermittent issue, implying that further repair may not be needed unless the code returns.

Mechanic-Grade Diagnostic Values

• LIN Bus Voltage (Communication Wire) — expected: When communicating, voltage toggles between approx. 1V (dominant) and 1V less than battery voltage (recessive, approx. 12V). At rest, should be a steady ~12V.. Failure: Voltage stuck at 0V, a constant intermediate voltage (e.g. 7-9V if not using peak measurement), or no voltage may indicate a short, open, or faulty module on the bus.
• Voltage Drop on Pump Power Supply Wire — expected: Less than 0.5V drop between the battery positive post and the pump connector's power pin while wiggling the harness and fuse.. Failure: A significant voltage drop (e.g., 5-7 volts as seen in one documented case) when wiggling the battery-top fuse block indicates a bad internal connection in the fuse block itself.

Hidden / Shadow Codes Worth Checking

• U1348: Engine Control Module LIN Bus Fault. This code indicates a general fault on the same communication line the coolant pump uses. A failing coolant pump module can disrupt the entire bus, causing this code to set alongside U0672. (see via Standard OBD-II scanner with manufacturer-specific code reading capability.)

Scan Tool Commands That Help

• GDS2 (GM Global Diagnostic System 2): Coolant Pump Test / Output Control — After verifying power, ground, and the LIN bus signal at the pump connector. This command attempts to run the pump directly, bypassing normal ECM control. If the pump runs during the test, the pump itself is likely good, and the issue is likely in the wiring or ECM. If it fails to run, the pump has failed internally.
• GDS2 (GM Global Diagnostic System 2): Cooling System Bleed Procedure — This is a mandatory procedure after replacing the electric coolant pump or servicing the cooling system. The function cycles the pump in a specific sequence to purge air trapped in the system. Failure to perform this bleed procedure can result in overheating and related codes even with a new, functional pump.

Wiring & Ground Locations

• K61 — Integrated into the Electric Engine Coolant Pump assembly.. This is the GM schematic designation for the Electric Engine Coolant Pump Control Module. The U0672 code specifically means 'Lost Communication With K61'.
• G59 Electric Engine Coolant Pump Connector — The 4-pin electrical connector on the pump body, located on the lower driver's side of the engine block.. This is the primary point of failure according to TSB PIP5863C. Inspecting and cycling this connector is the first diagnostic step.
• F54 (2019-2021) / F31 (2022-2024) — In the underhood fuse block, located in the engine compartment.. This 40A fuse supplies main power to the electric coolant pump. An internal short in the pump can blow this fuse, causing a loss of power and communication.
• G107 — A common engine ground point, typically located on the left front of the engine block.. A poor ground connection at this location could cause various electrical issues, including communication faults for modules grounded to the engine block.

Real Owner Repair Stories

• YouTube user 'Casi que motor' (2022 Chevrolet Silverado 1500 2.7L (platform mate with similar pump design)) — Check Engine Light with code U0672.
  ❌ Tried (didn't work) Initial diagnosis pointed to the water pump.
  ✅ What actually fixed it The electric water pump had an internal short to ground. Replacing the water pump and the blown 80-amp fuse in the battery fuse block resolved the issue.
• YouTube user 'RainmanRaysRepairs' (GM Truck with 2.7L L3B engine (platform mate with similar pump design)) — No communication with coolant pump, LIN bus codes.
  ❌ Tried (didn't work) A simple visual inspection of the fuse would not have revealed the fault.
  ✅ What actually fixed it A voltage drop test revealed a faulty internal connection in the battery-top fuse block. Wiggling the 80A fuse caused a 5-7 volt drop to the pump's power supply. Replacing the entire battery fuse block, not the pump, was the correct repair.

OEM Part Supersession History

• 12724522, 55506790, 55508939, 55510113, 55515497 → 12738953 — Likely internal revisions to improve reliability and address electronic failure modes seen in earlier versions.

Model Year Variations Within This Range

• 2019-2024: The fuse designation for the electric coolant pump in the underhood fuse block changed. For 2019-2021 models, it is typically fuse F54. For 2022-2024 models, it is fuse F31.