P0646

Symptoms

• Check Engine light comes on
• Air conditioner won't turn on
• Air conditioner relay does not click when turned on
• Warm air comes from the air ducts
• Other air conditioning system codes are also possible

Causes

• Short circuit of the relay control wire to ground
• Clutch relay malfunction (internal short circuit)
• Poor ground connection of ECU or relay
• Malfunction of the ECU output stage (relay control)
• Damage to wiring insulation

How to Fix

1. Check the voltage at the relay control contact with the air conditioner on
2. Replace A/C Relay
3. Check the control wire from the ECU to the relay for a short to ground
4. Check the quality of the ECU mass connection
5. If the code remains unchanged after replacing the relay and checking the wiring - ECU diagnostics

Related codes

Error P0646 by Vehicle Brand