01 How To Deactivate the Immobilizer From Your ECU (Complete G… • 02 The Benefits of ABS: Why You Need This Safety Feature in Yo… • 03 Tyre Burst At High Speed: What To Do And How To Stay Safe • 04 iStop: The Revolutionary Brake-Activated Auto Stop-Start Sy… • 05 P0104 - Mass Air Flow Circuit Intermittent • 06 Greener Roads: The Role of Catalytic Converters in Emission… • 07 Troubleshooting Black Smoke: Diagnosing Fuel-to-Air Issues … • 08 B0016 - Right Front or Passenger Frontal Deployment Loop (S… • 09 Drivers Are Accidentally Destroying Their Cars By Trusting … • 10 P0015 B Camshaft Position - Timing Over Retarded (Bank 1) •

DTC codes / P2Dxx · Hybrid propulsion / P2D68

P2D68Battery Charging System Negative Contactor C Control Circuit High

P2D68 indicates that the battery charging system's negative contactor control circuit is reporting a high voltage condition, meaning the control module has detected an open circuit or short to voltage on the wire that commands the negative contactor. The negative contactor is a high-current relay that connects the battery's negative terminal to the charging system, and when its control circuit is high, the contactor may fail to close, preventing the battery from charging or discharging properly.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaHybrid propulsion

Symptoms you may notice

  • Illumination of the battery/charging system warning light or a dedicated service vehicle soon message
  • The vehicle may fail to start or experience a no-crank condition due to a depleted battery
  • Electrical accessories may dim or behave erratically if the contactor does not close
  • The charging system may not charge the battery, leading to a dead battery after short drives
  • Often no symptoms besides the warning light, especially if the contactor remains closed by default
  • Possible reduced engine performance or stall if the contactor affects power supply to critical modules

Common causes, most likely first

  1. Open circuit or high resistance in the control wire between the control module and the negative contactor
  2. Short to voltage on the control circuit, often due to chafed wiring or moisture intrusion
  3. Faulty negative contactor coil or internal contactor failure
  4. Corroded or loose electrical connectors at the contactor or control module
  5. Failed control module driver for the contactor circuit
  6. Blown fuse or relay that supplies power to the contactor control circuit

How to diagnose and fix it

  1. Perform a visual inspection of the negative contactor, its connectors, and the control wiring for damage, corrosion, or loose pins
  2. Use a scan tool to command the negative contactor on and off and listen for an audible click; no click indicates a circuit or contactor fault
  3. Measure resistance of the contactor coil and compare to specification; an open or shorted coil requires contactor replacement
  4. Check for battery voltage on the control wire at the contactor with the key on; absence of voltage suggests an open circuit or faulty control module
  5. Inspect the control wire for a short to voltage by measuring voltage with the contactor disconnected and the control module commanding off
  6. Test the control module output with a test light or oscilloscope to confirm the driver is functioning
  7. Repair or replace damaged wiring, connectors, or the contactor as needed, then clear codes and verify the repair

Before you replace the negative contactor

  • A high control circuit code often results from a simple open circuit in the wiring harness rather than a failed contactor, so always check continuity and voltage drops before condemning the component.
  • Moisture intrusion into the contactor connector can cause a short to voltage that mimics a failed control module, so inspect for green corrosion or water tracks.
  • Some vehicles use a smart charging system where the negative contactor is normally closed; a high circuit may prevent it from opening, leading to a parasitic drain rather than a no-charge condition.
  • The control module may set this code if the contactor coil is disconnected during a battery replacement or service, so verify recent work before diagnosing.
  • A weak or failing battery can cause erratic control module behavior and set false high circuit codes, so always load-test the battery first.

Can I keep driving with P2D68?

If the warning light is on and the vehicle starts and runs normally, you can drive short distances to a repair shop, but avoid long trips or heavy electrical loads. If the battery is not charging or the vehicle fails to start, do not drive and seek immediate assistance.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage