P04D6

Symptoms

• Check Engine Light Is On
• The engine brake may engage involuntarily or may not work
• Reduced braking performance on descents
• Possible jerking when driving in engine braking mode

Causes

• Short circuit to power in the switch signal circuit
• Stuck engine brake switch
• Damage to wire insulation
• Moisture getting into the connector
• ECU malfunction

How to Fix

1. Read error codes and capture freeze frame data
2. Find the engine brake switch according to the diagram
3. Check the voltage in the signal circuit with the switch off
4. Disconnect the switch connector and check for voltage on the wire (if present, short to power)
5. Check the resistance of the switch and the serviceability of its contacts
6. Repair short circuit or replace damaged wire
7. Replace the switch if necessary
8. Reset the error and check the system operation

Related codes

Error P04D6 by Vehicle Brand