2020 Tesla Model X

Tesla Model X AC Charging Fault P0D35 — OBC Thermal Sensor Failure

P0D35 CHG_a053 CHG_a061 Published 2024-11-08 Updated 2024-11-08
Tesla Model X P0D35 OBC onboard charger thermal sensor AC charging

2020 Tesla Model X Long Range presented with AC charging failure at all Level 2 stations. DC Supercharging worked normally. P0D35 and CHG_a053 stored. Root cause was a failed thermistor inside the onboard charger assembly.

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The Problem
2020 Tesla Model X Long Range Plus (67,300 miles) presented unable to complete AC Level 2 charging sessions. Car would connect, display charging as started, then stop within 2-4 minutes with 'Charging Stopped — Check Charging Equipment'. DC Supercharging sessions completed normally. P0D35 (Charging System Fault), CHG_a053 (OBC temperature sensor), and CHG_a061 stored.
Diagnostic Procedure
  1. 1. Confirm fault codes. P0D35 and CHG_a053 present. Note that CHG_a053 specifically identifies OBC internal thermistor.
  2. 2. Verify DC charging works — confirmed via 30-minute Supercharger session with no faults. Rules out battery pack, BMS, and HV contactor issues.
  3. 3. Monitor OBC temperature sensor live data during AC charge attempt. Sensor reads -40°C from the moment charger initializes — physically impossible value indicating open circuit on thermistor.
  4. 4. AC charging control logic uses OBC thermistor to prevent thermal runaway. -40°C reading is interpreted as a sensor fault, and charging is terminated as a safety measure after a short timeout.
  5. 5. Inspect OBC coolant inlet temp vs OBC sensor. Coolant temp reads 22°C (ambient), confirming the thermistor is open-circuit, not a coolant flow problem.
  6. 6. Replace OBC assembly. Post-replacement thermistor reads 23°C — matches ambient. Clear codes.
  7. 7. Initiate Level 2 AC charge session. Charges to 100% without interruption. Fault codes do not return.
Resolution & Root Cause
OBC assembly replaced. Thermistor reads correctly, AC charging fully restored. DC charging unaffected throughout.
💡 Key Lesson
When a Tesla charges fine on DC Supercharger but fails on AC Level 2, the fault is almost always in the OBC (onboard charger), not the battery system. CHG_a053 with a -40°C OBC temp reading confirms an open-circuit thermistor. Replacing the charging equipment or testing at multiple stations wastes time — pull the live OBC temperature data first.
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.