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 is having trouble with the part that helps slow down the car using the engine. It's like when your bike's brakes aren't working properly.
The P04D6 code indicates a problem with the electrical circuit that controls the exhaust brake, which is used to slow down the vehicle by increasing engine backpressure.
The Exhaust Brake Input Circuit High code is triggered when the Powertrain Control Module (PCM) detects a high voltage condition in the exhaust brake input circuit. This could be due to a short to voltage or an open circuit, affecting the exhaust brake's ability to function properly.
• Exhaust brake not functioning
• Check Engine Light illuminated
• Reduced vehicle braking performance
• Faulty exhaust brake switch
• Wiring issues such as shorts or opens in the circuit
• Defective PCM
PCM: Powertrain Control Module
OBD-II: On-Board Diagnostics II
• Inspect the exhaust brake switch for damage or wear.
• Check the wiring and connectors for any signs of damage or corrosion.
• Test the voltage and continuity of the exhaust brake circuit.
• Replace the exhaust brake switch if faulty.
• Repair or replace damaged wiring or connectors.
• Reprogram or replace the PCM if necessary.
• Multimeter
• OBD-II scanner
• Basic hand tools
$100 - $500
Moderate
• Ford F-250
• Chevrolet Silverado 2500
• Ram 2500
• Regularly inspect and maintain exhaust brake components.
• Ensure wiring and connectors are free from corrosion.
• Use the exhaust brake regularly to ensure proper operation.
Sensor Issue
• Have the vehicle inspected by a professional if the Check Engine Light is on.
• Avoid heavy braking until the issue is resolved.
• Keep up with regular vehicle maintenance.
Check with your vehicle manufacturer to see if the exhaust brake system is covered under warranty.
The P04D6 code has been associated with diesel engines that use exhaust brakes to enhance braking performance.
Moderate – While the vehicle is still drivable, the braking performance may be compromised.
Always address Check Engine Light issues promptly to ensure safe vehicle operation.
• Vehicle engine running
• Exhaust brake engaged
The exhaust brake switch is typically located near the brake pedal or on the dashboard.
Q: Can I drive with the P04D6 code?
A: While it's possible to drive, it's not recommended as braking performance may be reduced.
Q: How can I reset the P04D6 code?
A: Fix the underlying issue first, then use an OBD-II scanner to clear the code.
Pro · Four-system diagnostics
A handheld scanner aimed at engine, transmission, ABS, and airbag diagnostic work.
Chassis and ABS faults usually need a scanner that can read brake-system data directly.
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Universal · Torque wrench
Useful when reassembly torque matters for wheel, suspension, and under-hood fasteners.
Useful when wheel, hub, or suspension hardware needs correct reassembly torque.
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Universal · Drive-on ramps
Helpful for safer access underneath the vehicle during exhaust, EVAP, and underbody inspection work.
Helpful for safer access during underbody inspection work.
View on AmazonThese are optional diagnostic tools, not guaranteed fixes. As an Amazon Associate I earn from qualifying purchases.