P0640

Symptoms

• Check Engine light comes on
• Difficulty starting in cold weather
• White smoke from the exhaust pipe during cold start (diesel)
• Unstable idle when warming up
• Increased fuel consumption in winter

Causes

• Intake air heater relay malfunction
• Blown heater circuit fuse
• Open or short circuit in heater wiring
• Malfunction of the heating element (broken spiral)
• ECU malfunction (rare)

How to Fix

1. Check the intake air heater circuit fuse
2. Check heater relay (replace with a known good one)
3. Check the heater supply voltage with the ignition on
4. Measure the resistance of the heating element with a multimeter
5. Inspect the heater wiring and connectors
6. Replace the faulty component (relay, heating element)

Related codes

Error P0640 by Vehicle Brand