P05F4

Symptoms

• Check Engine Light and Emission System Warning Light Illuminates
• Incorrect operation or complete failure of SCR/DPF
• Increased emissions
• Possible power limitation
• Unstable operation of the neutralization system relay

Causes

• Relay control circuit short to ground
• Damage to control wire insulation
• Internal defect of the relay control winding (short circuit of turns)
• Moisture getting into the relay connector
• ECU output stage malfunction

How to Fix

1. Read codes, check for related codes
2. Disconnect the control connector of the relay, measure the voltage on the control wire
3. Check the resistance of the control circuit to ground (with the computer turned off)
4. Inspect the wiring for pinches on metal parts
5. Check the connector for signs of moisture or corrosion.
6. Replace the relay or eliminate the short circuit in the control circuit

Related codes

Error P05F4 by Vehicle Brand