P0640 Fault Code

Intake Air Heater Control Circuit

• What does that mean?
• Symptoms
• Causes
• Solutions

The P0640 fault code indicates a problem with the Intake Air Heater Control Circuit. This error typically arises in diesel engine vehicles equipped with an intake air heater system that helps to preheat the incoming air for optimal combustion, especially in colder conditions. In such cases, the vehicle's Engine Control Module (ECM) detects an abnormality in the circuit responsible for controlling the intake heater operation, leading to this diagnostic code being triggered.

What are the symptoms of the P0640 code?

Drivers experiencing a P0640 fault code may notice several symptoms, including:

• Illuminated Check Engine Light: The most common and immediate indication of a fault.
• Reduced engine performance: The vehicle might exhibit sluggishness, particularly in cold weather conditions.
• Starting issues: Difficulty starting the engine, especially in low temperatures, can be a result of inadequate air heating.
• Increased emissions: As the vehicle struggles with combustion, it may produce higher levels of emissions.

What causes the P0640 code?

Several factors can contribute to the P0640 fault code. Common causes include:

• Open or shorted wires: Damage to the wiring harness connected to the intake air heater can lead to broken connections or electrical shorts.
• Faulty intake air heater: If the heater element is burned out or malfunctioning, it may disrupt the circuit.
• Malfunctioning ECM: The engine control module itself may be at fault or not properly communicating with the heater control circuit.

How to fix P0640?

To resolve the P0640 fault code, several steps should be taken:

• Diagnostic scan: Use an OBD-II scanner to verify the code and check for any related codes that could indicate other problems.
• Visual inspection: Examine the wiring and connectors associated with the intake air heater for damage or corrosion.
• Test the intake air heater: Measure resistance and functionality of the intake air heater. Replace it if it is found to be faulty.
• Check the ECM connections: Ensure that the ECM is functioning correctly and that there are no communication issues. Replace or reprogram as necessary.