P2D68

Code

Generic P — Powertrain

Battery Charging System Negative Contactor C Control Circuit High

Brand: Generic

Type: P — Powertrain

Views: UK: 14 EN: 23 RU: 17

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Page language: EN

Causes

Open or shorted wiring in the contactor C control circuit
Short to battery positive (B+) on the control wire
Damaged or internally shorted negative contactor (coil)
Faulty ECU/BCM driver (high-side/low-side transistor failure)
Corroded/loose connector or terminal at contactor, fuse, or module
Blown or incorrect fuse / faulty relay in control supply

Symptoms

Battery charging disabled or interrupted
HV battery or charge system warning lamp/message on dash
Vehicle may enter limp/limited functionality or refuse to start/drive (for hybrids/EVs)
DTC P2D68 stored and possibly other related contactor or charging codes
No audible click from contactor when commanded

What to check

Retrieve DTCs and freeze-frame data with a scan tool; note ignition/engine state when fault set
Visually inspect contactor C, harness, connectors, and associated fuses/relays for damage or corrosion
Use a scan tool to command contactor C ON/OFF and observe reported circuit status and any other related parameters
Back-probe the ECU/BCM control pin and the contactor coil terminal while commanding ON/OFF; record voltages
Measure coil resistance across the contactor terminals (with HV system made safe/disconnected per manufacturer instructions)
Check for continuity to battery positive and to chassis ground to detect unintended shorts or opens

Signal parameters

Expected control voltage (varies by design): typically ~0 V when driver pulls low, and near battery supply (e.g., 12 V or B+) when released — consult vehicle wiring diagram
Contactor coil resistance: common ranges — high-voltage contactors: ~0.1–5 ohms; low-voltage relay/solenoid coils: ~20–200 ohms. Refer to service spec
When commanded ON via scan tool: control circuit should change state (voltage or logic) and show continuity across contactor coil
A ‘Control Circuit High’ fault means the measured voltage is higher than the ECU/BCM expected threshold for a correct OFF/ON state

Diagnostic algorithm

Safety first: follow all high-voltage and battery isolation procedures before working on HV contactors. Disable HV system if required.
Connect a diagnostic scanner, clear codes, and attempt to reproduce the fault. Note conditions (IGN on, charging, vehicle off).
Visually inspect connectors, wiring insulation, and fuses/relays for damage, melting, corrosion, or rodent chew.
With harness accessible, back-probe the control wire at the ECU/BCM and at the contactor while commanding the contactor ON/OFF. Compare voltages to specifications.
Check for short to B+: with ignition off and HV isolated, measure resistance between the control wire and battery positive. A low resistance indicates a short to B+.
Check for open/high-resistance to ground: measure continuity from control wire to the ECU driver ground reference when commanded to pull low.

Likely causes

Wiring short to B+ between ECU/BCM and contactor C
Open or high-resistance ground in the contactor/coil circuit
Failed contactor coil with internal short to battery
Defective driver output in the ECU/BCM
Connector corrosion or damaged insulation creating intermittent high voltage

Fault status

⚠️ Status

Battery Charging System Negative Contactor C Control Circuit High — control circuit voltage higher than expected. This can prevent the negative contactor from operating and may disable battery charging. Inspect wiring, contactor, fuses/relays, and controller output.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours