What Does It Mean?
This generic powertrain diagnostic trouble code (DTC) generally applies to all OBD-II equipped vehicles that have an air intake heater, including but not limited to Chevrolet GMC (Duramax), Ford (Powerstroke), Honda, Nissan, Dodge, etc.
This code is one of several possible codes associated with a malfunction in the air intake heater circuit. An air intake heater is a critical component for a diesel engine to assist the starting process. The five codes that the Powertrain Control Module (PCM) can set for issues with the “A” air intake heater circuit are P0540, P0541, P0542, P0543, and P2604.
What is an Air Intake Heater For?
The “A” air intake heater circuit is designed to operate the components that provide hot air to facilitate the starting and idling of the diesel engine at various temperatures. The typical air intake heater circuit includes a heating element, relays, a temperature sensor, and at least one fan. Air ducts are also required to route the hot air to the intake connections, and electrical wiring controls the operation of these components.
The P0540 fault code is triggered by the PCM when it receives an abnormal signal from the “A” air intake heater circuit. The circuit may be out of range, contain a faulty component, or have poor airflow. Various circuit malfunctions may be present and can be physical, mechanical, or electrical.
The P0540 code is set when the PCM detects a malfunction in the “A” air intake heater circuit.
Here is an example of an air intake heater:
Code Severity and Symptoms
The severity of this code is normally moderate but can be severe depending on the specific malfunction.
Symptoms of a P0540 diagnostic trouble code may include:
Engine does not start
Longer than normal starting time
Check Engine Light illuminated
Rough idle in cold weather
Engine stalls
Causes
Typically, potential causes of this code include:
Faulty heating element relay
Defective heating element
Faulty temperature sensor
Corroded or damaged connector
Damaged or restricted air duct
Faulty or damaged wiring
Faulty blower motor
Faulty PCM
Another style of air intake heater:
What are the most common repairs?
Replacing the heating element
Replacing the temperature sensor
Replacing the heating element relay
Cleaning corrosion from connectors
Repairing or replacing wiring
Replacing damaged air ducts
Replacing the fan motor
Flashing or replacing the PCM
Diagnostic and Repair Procedures
The first step in the troubleshooting process for any malfunction is to search for Technical Service Bulletins (TSBs) for the specific vehicle by year, model, and powertrain. In some circumstances, this can save you a lot of time in the long run by pointing you in the right direction.
The air intake heater circuit may not operate automatically if the ambient air or engine temperature is above the limit set by the manufacturer. The circuit should activate if it is commanded “ON” with a scan tool, or if power is applied manually.
Basic Steps
Check the heating element, does it turn “ON”
NOTE: Do not touch the heating element or heat shield
Check the blower motor, does it turn “ON”
Visually inspect the circuit connections and wiring for defects
Visually inspect the condition of the air ducts for obvious defects
Check electrical connections for security and corrosion
Advanced Steps
Advanced steps become very vehicle-specific and require appropriate advanced equipment to perform accurately. These procedures require a digital multimeter and vehicle-specific technical references. Voltage requirements will be highly dependent on the specific year, model, and diesel engine of the vehicle.
Specific Checks:
Note: On applications equipped with mass air flow sensors, the intake air temperature sensor is integrated into the sensor body. Consult technical data to determine the correct pins associated with the sensor.
Specific checks should be performed using the troubleshooting guidelines for the specific vehicle, using the technical manual or online reference material. These steps will guide you through the process of checking the power and ground for each component in the air intake heater circuit in the correct order. If the voltage is correct for a component that is not operating, that component is likely faulty and needs replacement. If power is not available to operate the circuit, continuity checks may be necessary to identify faulty wiring or components.
I hope the information in this article has helped point you in the right direction to correct your air intake heater circuit malfunction issue. This article is strictly informational, and the technical data and service bulletins specific to your vehicle should always take priority.