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 car's computer is getting too much electricity from the main relay, which is like a switch that helps turn on the car's engine and other important parts.
The main relay is responsible for supplying power to the vehicle's electronic control unit (ECU) and other critical components. Overvoltage means that the voltage level is higher than expected, which can cause damage to electrical components.
P164B is triggered when the powertrain control module (PCM) detects a voltage level from the main relay that exceeds the manufacturer's specified range. This can lead to potential damage to the ECU and other sensitive electronic components.
• Check Engine Light is on
• Engine may not start or stall
• Electrical components may malfunction
• Faulty main relay
• Wiring issues such as shorts or corrosion
• Faulty alternator causing overcharging
Relay: An electrically operated switch used to control a circuit.
Overvoltage: A condition where the voltage in a circuit exceeds the normal operating range.
• Inspect the main relay and its connections for damage or corrosion.
• Check the vehicle's battery and alternator for proper voltage output.
• Test the wiring between the main relay and the ECU for shorts or opens.
• Replace the faulty main relay.
• Repair or replace damaged wiring.
• Replace or repair the alternator if it is overcharging.
• Multimeter
• Relay tester
• Diagnostic scan tool
$100 - $300
Moderate
• Volkswagen Golf
• Audi A4
• BMW 3 Series
• Regularly inspect and maintain battery and alternator.
• Check and clean electrical connections periodically.
• Replace relays at recommended intervals.
Electrical Issue
• Do not ignore the Check Engine Light.
• Have the vehicle inspected by a professional if you notice electrical issues.
• Regular maintenance can prevent this issue.
Check with your vehicle manufacturer for warranty coverage on electrical components.
This code has been more common in vehicles with aging electrical systems or those with aftermarket electrical modifications.
Moderate – It should be addressed soon to prevent potential damage to the vehicle's electrical system.
Driving with electrical issues can lead to further damage or unsafe driving conditions. Always address Check Engine Light warnings promptly.
• Vehicle at operating temperature
• Electrical system under load (e.g., lights, radio on)
The main relay is typically located in the engine compartment fuse box or relay panel.
Q: Can I drive with a P164B code?
A: It's not recommended to drive with this code as it can lead to further electrical issues or damage.
Q: How can I prevent a P164B code from occurring?
A: Regular maintenance of the electrical system and components can help prevent this issue.
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