P0647

Symptoms

• Check Engine light comes on
• The air conditioner can be constantly on
• Increased load on the engine (reduced power)
• The air conditioner does not respond to the off button
• The compressor runs constantly, causing noise

Causes

• Short circuit of the relay control wire to the power source
• Relay fault (contacts closed)
• Wiring harness insulation damage
• ECU output stage malfunction (no ground)
• Incorrect connection after repair

How to Fix

1. Check the voltage at the relay control contact with the air conditioner turned off (should be about 0 V)
2. Replace A/C Relay
3. Check the control wire from the ECU to the relay for a short to positive
4. Inspect the wiring harness for damaged insulation
5. Check the operation of the ECU output stage (diagnostics on the bench)
6. If necessary, repair or replace the ECU

Related codes

Error P0647 by Vehicle Brand