01 Can a Hybrid Car Survive a Flood? Understanding the Risks a… • 02 GM's Oshawa Plant Gets a C$280M Boost for Next-Gen HD Picku… • 03 What Happens When the Throttle Body Gets Dirty • 04 Pushing the Limits: How Long Can You Really Go Without an O… • 05 The Hidden Cause of Poor Fuel Economy After Basic Repairs • 06 Demystifying OBD-II Trouble Codes: An In-Depth Look at Auto… • 07 This is How Synthetic Oil Can Make or Break Your Engine’s L… • 08 Porsche vs. Mercedes vs. BMW vs. Audi: Which Brand Will Las… • 09 Why Spare Parts Shops Are One of the Most Profitable Busine… • 10 The Business of Car Importation: Profits and Risks Explained •

DTC codes / P2Dxx · Hybrid propulsion / P2D08

P2D08Motor Electronics Coolant Pump B Supply Voltage Circuit

P2D08 indicates that the engine control module (ECM) has detected an abnormal voltage condition on the power supply circuit for the motor electronics coolant pump 'B'. This pump is typically an electric auxiliary pump used to circulate coolant through the turbocharger or other components, and the ECM monitors its supply voltage to ensure it is within the expected range. The code is set when the voltage is too low (open circuit, high resistance) or too high (short to voltage), indicating a fault in the power feed to the pump.

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

Symptoms you may notice

  • Illumination of the check engine light (malfunction indicator lamp).
  • Often no symptoms besides the warning light, especially if the pump is not critical for basic engine operation.
  • Possible overheating of the turbocharger or related components under heavy load or after engine shutdown.
  • Reduced engine performance or power derate in some vehicles to protect the turbocharger.
  • Coolant warning light or message on the dashboard in vehicles that monitor coolant temperature closely.
  • Auxiliary coolant pump may not run, leading to poor heater performance or delayed cabin heat.

Common causes, most likely first

  1. Faulty motor electronics coolant pump 'B' (internal short or open circuit).
  2. Damaged or corroded wiring harness or connector at the pump.
  3. Blown fuse or fusible link supplying power to the pump circuit.
  4. Poor ground connection for the pump or its control module.
  5. Faulty relay or power supply control module (if equipped) that feeds the pump.
  6. Corrosion or water intrusion in the connector causing high resistance.
  7. ECM internal fault (rare) misinterpreting the voltage signal.

How to diagnose and fix it

  1. Verify the code with a scan tool and check for any related codes in other modules.
  2. Inspect the pump connector and wiring for signs of damage, corrosion, or loose pins.
  3. Check the fuse and relay that supply power to the coolant pump circuit.
  4. Measure voltage at the pump connector with the key on and engine off; compare to battery voltage.
  5. Perform a voltage drop test on the power and ground circuits to identify high resistance.
  6. If voltage supply is correct, test the pump motor resistance or command the pump on with a scan tool to see if it operates.
  7. Replace the pump or repair the wiring as needed, then clear codes and verify the repair.

What the supply voltage code really means

  • This code is often set by a simple blown fuse that also powers other components, so check fuses first before condemning the pump.
  • A pump that runs quietly does not guarantee the supply circuit is healthy; voltage drops under load can set the code intermittently.
  • The ECM may set this code if the pump draws too much current, which can be caused by a failing pump motor or a restricted coolant flow.
  • On some vehicles, the auxiliary coolant pump only runs after engine shutdown, so the fault may not appear during a short test drive.
  • Do not overlook the ground circuit; a poor ground can cause the ECM to see low voltage on the supply side even if the power wire is good.

Can I keep driving with P2D08?

It is generally safe to drive with this code if the engine temperature remains normal, but avoid heavy loads or aggressive driving that could overheat the turbocharger. Have the fault diagnosed soon to prevent potential damage to the turbocharger or other components that rely on the auxiliary coolant pump.

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