U0672 on 2020-2024 Cadillac XT6: Coolant Pump Communication Failure Causes and Fixes

What's Unique About the 2020-2024 Cadillac XT6

The Cadillac XT6 with the 2.0L LSY turbo engine uses a sophisticated Active Thermal Management system instead of a traditional thermostat. Coolant flow is managed electronically by the pump. General Motors has issued specific Technical Service Bulletins (TSBs) for the XT6 and numerous other models with this engine, acknowledging that a poor electrical connection at the pump is a common cause for this code, often not requiring pump 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 temperature gauge rising rapidly into the red zone.
• Warning messages on the driver information center like "Engine Overheated".
• Loss of cabin heating, with vents blowing cold air.
• Engine may enter a reduced power or "limp mode".
• Engine cooling fans may run constantly at high speed, even when the engine is cold.

Most Likely Causes

1. Poor Connection at the Electric Engine Coolant Pump 🔴 High Probability GM has issued TSBs #PIP5863B and #PIP5863C specifically identifying this as a known issue. The connector can suffer from contamination, poor terminal tension, improper crimp, or backed-out pins.
   How to confirm: Visually inspect the wiring harness and 4-pin connector at the electric coolant pump. Check for dirt, damage, or backed-out pins. Per TSB guidance, check for proper terminal tension and then simply unplug and securely replug the connector ('cycling the connection'). This alone can resolve the issue.
   Typical fix: Clean the connector terminals and apply dielectric grease. Ensure the connector is fully seated and locked. If the code does not return, the repair is complete. GM allocates 0.3 labor hours for this inspection under warranty.
   Est. part cost: $0-$15
2. Failed Electric Engine Coolant Pump 🟡 Medium Probability The pump contains an integrated control module that can fail internally due to electronic faults. If the connection is good but communication cannot be restored, the pump assembly is the next likely point of failure.
   How to confirm: After confirming the wiring and connector are intact and have proper power and ground, the pump module is the suspected cause. Diagnosis may require a scan tool capable of communicating directly with the pump module on its specific LIN bus.
   Typical fix: Replace the entire electric engine coolant pump assembly. The latest OEM part number is 12738953, which supersedes previous versions.
   Est. part cost: $250-$400
3. Damaged Wiring Harness ⚪ Low Probability Another TSB, #23-NA-074, notes that the wiring harness can chafe on the battery tray support bracket, causing a variety of communication codes, including U0672.
   How to confirm: Inspect the wiring harness in the area around and under the battery tray for signs of rubbing, exposed wires, or pinching against sharp metal edges.
   Typical fix: Repair the damaged wires and protect the harness from future chafing using anti-abrasion tape or conduit. The TSB recommends applying strips of deadener material to the sharp edges of the bracket to prevent recurrence.
   Est. part cost: $10-$50

Rare But Worth Checking

• Internal Pump Circuit Board Defect:

Diagnosis Steps

1. Verify the code U0672 is present using an OBD-II scanner. Check for other related codes like U1348.
2. Let the engine cool completely before beginning work.
3. Locate the electric engine coolant pump. On the 2.0L LSY engine, it is typically on the lower side of the engine.
4. Carefully inspect the 4-pin electrical connector (X327) and the wiring harness leading to the pump. Look for any signs of corrosion, contamination, or physical damage.
5. As per TSB #PIP5863C, disconnect the connector. Inspect the terminals for proper tension, ensure they are not backed out, and check for any crimp or lock issues.
6. Securely reconnect the connector. This is known as 'cycling the connection'.
7. Clear the trouble code with the scanner.
8. Start the engine and let it run to see if the code returns. If it does not, TSB guidance suggests the issue is resolved and the vehicle can be returned to the customer.
9. If the code returns, inspect the wiring harness for chafing, particularly around the battery tray support bracket as noted in TSB #23-NA-074.
10. If the wiring and connection are confirmed to be good, the electric engine coolant pump assembly is the most likely cause of the failure and should be replaced.

Parts You'll Likely Need

• Electric Engine Coolant Pump (OEM #12738953) — This part is replaced if the integrated control module fails, which is the most common cause after a poor connection is ruled out.
  Trusted brands: ACDelco
  OEM price range: $300-$400
  Aftermarket price range: $200-$300
• Electric Coolant Pump Connector Pigtail (OEM #ACDelco PT2923 (example, verify fitment)) — If the connector housing or terminals are found to be corroded, melted, or damaged during inspection, a new pigtail must be spliced into the harness.
  Trusted brands: ACDelco, Dorman
  OEM price range: $25-$50
  Aftermarket price range: $15-$30

Related Codes That Often Appear With This One

• P26BB — This code relates to the coolant flow control valve, which works in conjunction with the electric water pump as part of the Active Thermal Management system. A communication failure with the pump can lead to faults with associated components.
• U1348 — This code indicates a fault on the LIN Bus. Since the electric coolant pump communicates over a LIN bus, a U0672 is often accompanied by a general bus fault code like this.

Technical Service Bulletins (TSBs) & Recalls

• PIP5863C / PIP5863B: Addresses MIL on with DTC U0672. Advises technicians to inspect the electric engine coolant pump connection for contamination, terminal tension, and crimp issues, then cycle it and clear the code before performing further diagnostics. Notes that if the code does not return, the issue is resolved.
• 23-NA-074: Notes that wire chafing on the battery tray support bracket can cause a host of intermittent electrical and communication DTCs, including U0672. Recommends repairing the wire and applying deadener material to the bracket.

Platform-Specific Known Issues

• A known issue, documented in GM TSBs PIP5863B and PIP5863C, points to a problem with the electrical connection to the pump. This issue is not unique to the XT6 and affects a wide range of GM vehicles using the 2.0L LSY engine.