2021 Cadillac XT6 Problems: 16 Known Issues

On the 2020-2021 Cadillac XT6 3.6L V6 LGX, gM bulletin 21-NA-108 (which superseded PIP5257E) covers engine overheating with the cooling system contaminated by engine oil, and it lists the 2020-2021 Cadillac XT6 with the 3.6L LGX V6 among the affected applications. The failure is not a head gasket in the usual sense: pressurized oil from the main oil gallery migrates into a coolant water jacket through porosity or a thin-wall casting defect in the engine block. Because oil pressure is far higher than coolant pressure, oil pushes into the coolant rather than the other way round, and the surge tank and radiator fill with a thick brown oil-and-coolant emulsion that looks like a milkshake. That emulsion will not carry heat, so the engine overheats, and it plugs the radiator and heater core. GM bulletins 21-NA-147 and 22-NA-240 cover the related diagnosis of a coolant and/or oil leak with the malfunction indicator lamp on. This is engine-code specific — it is an LGX 3.6L casting issue and is not a claim about the 2.0L LSY turbo four also sold in the XT6.

On the 2021-2024 Cadillac XT6 2.0L Turbo I4 (LSY), gM bulletin PIP5863B addresses an illuminated malfunction indicator lamp with DTC U0672, lost communication with electric engine coolant pump G59. Its North American applicability includes XT6 vehicles with the 2.0L LSY engine. A pump-connection problem is a potential cause; the code alone does not establish a failed pump.

On the 2020-2023 Cadillac XT6 3.6L V6 (LGX), p0128 requires diagnosis before replacing parts. PIP5940 covers thermostat replacement on 2020–2023 XT6 vehicles with the 3.6L LGX and changes the repair to the thermostat housing rather than an unnecessary pipe-and-outlet assembly. It does not establish a failure rate. Separately, GM 22-NA-054 identifies a possible ECM calibration timing error on 2021 XT6 LGX vehicles with P0128, a check-engine warning, an inoperative temperature gauge or fans running after shutdown.

On the 2021-2023 Cadillac XT6, an internal short inside the K111 Fuel Pump Driver Control Module (FPDCM, also called the fuel pump power control module) can cause a cluster of drivability faults on 2021-2023 Cadillac XT6 vehicles. GM documented this first as preliminary information PIP5964 and then as service bulletin 24-NA-139, published July 2024, which replaces PIP5964D. The symptom set is broad and misleading: crank-but-no-start, stalling while driving, loss of power, rough idle, erratic shifting, and an inoperative or erratic fuel gauge, all with the check engine light on and multiple codes stored. Because the module drives fuel pump speed, technicians may chase a failing in-tank pump or a transmission concern before finding the module. The bulletin directs module replacement when P023F and/or P129F are set and diagnostics find no other cause. Owner reports of the failure exist on the Cadillac Owners Forum, including a 2021 XT6 Sport that would not start with P023F stored.

On the 2020-2025 Cadillac XT6, the auto start-stop system engages and disengages harshly, causing the vehicle to shudder on restart. The AGM battery required for the system degrades quickly, and when it weakens, the start-stop system becomes erratic or disables itself. Many owners find the system intrusive.

On the 2021 Cadillac XT6, if you own a 2021 Cadillac XT6, this one is worth a VIN check. GM recalled a limited group of 2021 XT6, XT5 and GMC Acadia vehicles because the fuel supply lines may have been improperly attached and seated at the factory. NHTSA's consequence statement is blunt: lines that are not properly seated may loosen or separate, causing a fuel leak, which increases the risk of a fire. The whole campaign covers 572 vehicles across all of the models listed, so inclusion is the exception rather than the rule for the XT6 — but the potential outcome is serious enough that verifying by VIN is the right move rather than waiting to notice a problem. GM's internal recall number is N212335590, and owner letters were mailed July 1, 2021.

On the 2020-2023 Cadillac XT6, xT6 owners report a "Steering Assist is Reduced — Drive with Care" or "Service Power Steering" message in the driver information center, usually with a noticeable increase in steering effort. GM bulletin 20-NA-215 covers this condition on the XT5 and XT6 and ties it to DTCs C0460 and/or C0545 stored in the power steering module. The XT6 uses a belt-drive electric rack with the motor and control module integrated into the steering gear, so an internal fault or a torque-sensor signal fault sets the code and the module deliberately cuts or reduces assist rather than allowing erratic assist. Steering is still mechanically connected — the car remains steerable — but effort rises sharply, which is most alarming at parking-lot speeds or in an evasive maneuver. Owners also describe a separate, milder version where assist fades after sustained low-speed maneuvering and returns once the system cools; that thermal derate is normal protection, not a failed rack, and it clears itself.

On the 2020-2023 Cadillac XT6, the XT6's GM 9T65 9-speed automatic transmission exhibits shuddering during light throttle acceleration between 25-50 mph, similar to driving over rumble strips. The torque converter clutch wears prematurely, contaminating the transmission fluid.

On the 2020-2021 Cadillac XT6, gM PIP5608F covers 2020-2021 XT6 vehicles with 9-speed transmissions RPO M3G or M3W when torque-converter clutch shudder occurs on re-apply after a shift at 40 mph or below. GM identifies possible excessive assembly lubricant in the fluid and requires confirmation with TCC slip data or the scan-tool command test.

On the 2021-2025 Cadillac XT6 2.0L Turbo I4 (LSY), gM bulletin 21-NA-240 describes an engine oil leak that may result from the amount of sealant at the LSY camshaft-carrier gasket. Oil can appear to originate at another front-engine joint. The bulletin directs technicians to locate the actual leak before selecting a repair; it does not establish that every equipped XT6 has this condition.

On the 2020-2025 Cadillac XT6, the XT6 uses the GM 3.6L V6 (LGX) which has a documented history of timing chain stretch across the GM lineup. While the LGX generation is improved over earlier 3.6L variants, the three-chain design with plastic guides remains a long-term reliability concern. Most XT6s are still too new for widespread timing chain failures, but owners should monitor for early signs and plan for preventive replacement around 100,000-120,000 miles based on the engine's history in other models.

On the 2020-2021 Cadillac XT6, if your 2020 or 2021 Cadillac XT6 was ordered with the optional Surround Vision feature, it may be part of NHTSA recall 22V709000. GM found that the coaxial cable connectors carrying the rearview camera signal may have been crimped improperly, and a faulty crimp can cause the rearview camera to fail outright or work only intermittently. The practical effect for an XT6 driver is a missing or unreliable rear image when reversing, which NHTSA notes reduces rear visibility and increases crash risk. XT6s without Surround Vision are not covered. The campaign as a whole spans 95,231 vehicles across all the models it includes - that number is for the entire campaign and says nothing about how many XT6s are involved. GM tracks the recall internally as N222378380 and mailed owner letters on January 18, 2023.

On the 2020-2025 Cadillac XT6, the Power Transfer Unit (PTU) on AWD-equipped XT6 models develops seal leaks that allow fluid to seep out. Low PTU fluid causes the internal gears and bearings to wear prematurely, eventually producing a whining noise. The PTU is not included in routine maintenance schedules, so leaks often go unnoticed.

On the 2020-2021 Cadillac XT6, gM bulletin 19-NA-167 covers water leaking into the interior on the 2020-2021 Cadillac XT6 (alongside the 2017-2021 XT5 and GMC Acadia). Owners find wet carpet or headliner at the front and/or rear, on either side, typically after rain or a car wash. The cause is not the sunroof drains that owners and shops usually chase first: it is pinhole voids in the laser braze joint between the roof panel and the outer body ring, and in the seam sealer over it. The bulletin says the pinholes are most often found near the top of the windshield at the A-pillars, or near the top of the liftgate at the D-pillars. Water entering at the D-pillars runs down into the rear of the vehicle, and the bulletin specifically notes that on the XT6 the liftgate actuator may become noisy or inoperative as a result — so an electrical complaint at the tailgate is a symptom of the body leak, not a separate failure. Left alone, trapped water rots carpet padding, grows mold, and corrodes rear body connectors.

On the 2021-2023 Cadillac XT6, owners of 2021-2023 Cadillac XT6 vehicles built before the bulletin's VIN breakpoint report a grinding or groaning noise from the front brakes on the first few stops, particularly after the vehicle has sat overnight. It may feel like the ABS is active even though it is not. GM bulletin 21-NA-142 (current revision January 2025) says the cause may be the front disc brake pad material and has technicians check the pad stamp (GM9130 or GM9140). The same bulletin also covers the Buick Enclave, Cadillac XT5, Chevrolet Blazer and Traverse, and GMC Acadia within listed VIN ranges.

On the 2020-2022 Cadillac XT6, gM bulletin 22-NA-094, issued July 2022, addresses a loss of cabin heat on the Cadillac XT6 and XT5. Owners get little or no warm air from the vents even after the engine reaches operating temperature — the complaint typically shows up in cold weather and is easy to misdiagnose as a stuck thermostat, an air pocket in the cooling system, a blend door actuator, or a plugged heater core. GM traced it instead to a software anomaly in the engine control module: the ECM's thermal management strategy does not bring coolant temperature up or route flow to the heater core as intended, so the heater has nothing hot to work with. Because the fault is calibration rather than hardware, no part is actually broken, and owners who let a shop chase it mechanically can spend hundreds of dollars replacing a perfectly good thermostat or heater core before the real fix is applied.