2024 GMC Sierra EV

GMC Sierra EV P0D35 OBC Fault — Ground Fault at Charge Inlet Wiring

P0D35 U3003 Published 2025-04-08 Updated 2025-04-08
GMC Sierra EV P0D35 OBC ground fault charge inlet wiring

2024 GMC Sierra EV Denali presented with P0D35 and intermittent AC charging failure. DC Ultium fast charging unaffected. Ground fault found in the AC charge inlet wiring harness where it enters the OBC — caused by a loose retaining clip allowing harness movement and abrasion.

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The Problem
2024 GMC Sierra EV Denali (8,900 miles) presented with intermittent AC Level 2 charging failure. DC fast charging at Ultium/EVgo stations worked normally. P0D35 (Charging System Fault) and U3003 stored. Only 8,900 miles — unexpected on a nearly new vehicle.
Diagnostic Procedure
  1. 1. Confirm P0D35 and U3003. DC charging normal — rules out battery and BMS.
  2. 2. AC charging path: measure AC input voltage at OBC during Level 2 attempt — 240V present. OBC output: 0V. OBC not converting.
  3. 3. Check OBC ground resistance. Measure OBC chassis ground to vehicle chassis: reads 4.2 ohms — should be <0.1 ohms. High ground resistance would cause OBC to fault on over-voltage on the floating ground.
  4. 4. Trace OBC ground path. Ground wire runs from OBC through a retaining clip on the firewall to the main chassis ground lug.
  5. 5. Inspect retaining clip — clip was installed but not fully engaged at the factory, allowing the ground wire to vibrate against a sharp firewall edge. At 8,900 miles, minor abrasion has increased resistance without yet causing visible damage.
  6. 6. Re-route ground wire with full clip engagement and additional protective sleeve at contact point.
  7. 7. OBC ground resistance: 0.04 ohms. AC Level 2 charging initiated — full 11.5kW session completes. P0D35 does not return.
Resolution & Root Cause
OBC ground wire re-routed and properly secured. Ground resistance reduced to 0.04 ohms. AC charging fully restored.
💡 Key Lesson
P0D35 AC charging fault on a nearly new GMC Sierra EV points to a manufacturing or assembly issue rather than component failure. High OBC ground resistance from an improperly secured ground wire is the failure mode here — a $0 repair found by measuring ground resistance before any part replacement.
About This Case

This case was solved remotely by an HVDesk specialist with 15+ years of hands-on experience across major EV platforms including Tesla, Hyundai/Kia, Volkswagen ID series, BMW i-series, and Ford EVs. The procedure was provided as structured remote support to an independent auto repair shop.