2023 GMC HUMMER EV PICKUP

Symptoms: Reduced propulsion power warnings on dash, Vehicle enters limp mode or won't exceed 40 mph, Coolant smell or visible leaks near front subframe, Check Engine light with P0AC0 or P1A42 codes

Fix: Inverter coolant loop uses separate circuit from battery thermal management. Failures often trace to clogged filters, pump failures, or leaking connections at the power electronics cooling module (PECM). Inverter R&R requires 8-12 hours if component itself fails—typical indie shops can't test these, so you're throwing parts. GM warranty covers most, but post-warranty you're looking at dealer-only repair.

Estimated cost: $4,500-8,000

Typical onset: 15,000-40,000 mi

Symptoms: Whining or grinding noise that increases with speed, Clunking on initial acceleration from stop, Metal shavings visible in transmission fluid during service, Drive unit leaking fluid from output seal

Fix: GM calls it an 'eAxle' but it's still a gearbox—just one fixed ratio. Early units show premature bearing wear on output shafts, likely from inadequate lubrication at high torque launches. Repair requires complete drive unit R&R, typically 10-14 hours per axle. Tri-motor trucks have three of these units. Front differential rebuild often needed simultaneously if metal contamination spread. This is warranty-claim territory—post-warranty, independent shops struggle with Ultium drivetrain programming.

Estimated cost: $6,000-12,000

Symptoms: Sudden range loss (50-100 miles) without warning, Battery pre-conditioning doesn't complete, Dashboard shows 'Service High Voltage Charging System', Uneven State of Charge between module groups visible on scan tool

Fix: The 200+ kWh pack uses 24 modules. When one cell group fails to balance, entire range takes a hit. GM's solution is module replacement—not individual cell repair. Module R&R is 6-8 hours if underneath panels cooperate; add 2-3 hours for diagnosis with factory scan tools. Independent shops can't touch this without GM SPS programming access. Some failures traced to water intrusion through underbody skid plate bolts.

Estimated cost: $3,000-7,500

Typical onset: 20,000-50,000 mi

Symptoms: Extract mode (6-inch lift) won't engage or raises unevenly, Air compressor runs constantly or not at all, 'Service Suspension System' warning on cluster, Vehicle drops to bump stops overnight

Fix: The adaptive air suspension sees heavy duty cycles with Extract mode abuse—many owners treat it like a daily party trick. Compressor overheats or actuator solenoids stick. Compressor replacement is 4-5 hours; full corner actuator is 3-4 hours. Parts are Hummer-specific, no aftermarket yet. Air line fittings at subframe also crack from flex during articulation. This isn't your Denali air ride—components are overworked from day one.

Estimated cost: $2,200-4,800

Symptoms: AC blows warm intermittently despite full refrigerant, Moisture or oily residue on passenger floor, Clicking from dash when AC cycles on, Climate control screen freezes or resets randomly

Fix: Evaporator core leaks require full dash removal—16-18 hours labor. Some cases resolve with software reflash of HVAC module (1 hour, dealer-only), but physical leaks are material defects. GM used new eco-friendly refrigerant (R-1234yf) in ultra-tight coils that corrode faster than R-134a systems. If it's actually leaking, you're in for a week at the dealer. Many get bandaided with stop-leak until warranty expires.

Estimated cost: $3,500-6,000

Symptoms: Vehicle won't wake from sleep mode, dead 12V battery, Phantom electrical loads detected during parasitic draw test, Infotainment won't boot or stuck in loop, Door locks cycle randomly when parked

Fix: Like all modern EVs, the 12V system runs accessories while the HV battery stays isolated. Gateway control module (which bridges dozens of CAN networks) fails to sleep properly, draining the 12V in 3-5 days. Replacement is 2-3 hours but requires Techline subscription for programming. Some fixed with software updates, others need hardware swap. Always load-test 12V battery first—AGM failures mimic module issues. GM extended warranty on some VINs quietly.

Estimated cost: $800-1,800