Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means that the computer in your car has detected a problem with the part that helps warm up the engine coolant. It's like when your electric blanket has a broken wire and can't heat up properly.
The P2B78 code is triggered when the engine control module (ECM) detects a high voltage condition in the control circuit for the second coolant heater.
The P2B78 code indicates that the ECM has found an abnormally high voltage in the control circuit of the Coolant Heater B. This could be due to a short circuit, a faulty heater, or an issue with the wiring or connectors.
• Check Engine Light is on
• Engine takes longer to reach operating temperature
• Poor heater performance
• Faulty Coolant Heater B
• Short circuit in the wiring
• Poor electrical connection
ECM: Engine Control Module
OBD-II: On-Board Diagnostics, Second Generation
• Use an OBD-II scanner to confirm the code.
• Inspect the wiring and connectors for damage.
• Test the coolant heater for proper operation.
• Repair or replace damaged wiring.
• Replace the faulty coolant heater.
• Ensure all connections are secure and free of corrosion.
• OBD-II scanner
• Multimeter
• Wrench set
$150 - $400
Moderate
• Toyota Prius
• Honda Accord Hybrid
• Chevrolet Volt
• Regularly inspect electrical connections.
• Perform routine maintenance checks.
• Use quality replacement parts.
Sensor Issue
• Do not ignore the Check Engine Light.
• Have the vehicle inspected by a professional.
• Avoid driving the vehicle until the issue is resolved.
Check with your vehicle manufacturer for warranty coverage on emissions-related components.
P2B78 is a relatively uncommon code, typically associated with hybrid and electric vehicles that use coolant heaters to manage engine temperature.
Moderate – This issue should be addressed soon to prevent potential engine performance issues.
Driving with a malfunctioning coolant heater can lead to engine performance issues and increased emissions.
• Engine at operating temperature
• Vehicle stationary
The coolant heater is typically located near the engine block or in the cooling system circuit.
Q: Can I drive my car with a P2B78 code?
A: It's best to have the issue checked as soon as possible to avoid potential engine performance issues.
Q: Will the P2B78 code cause my car to overheat?
A: It may not cause immediate overheating, but it can affect how quickly your engine reaches optimal temperature.
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