AutoCodes – Generic – P0540

P0540 Code - Intake Air Heater 'A' Circuit

Quick Answer

The Engine Control Module (ECM) uses an Intake Air Heater (IAH) to warm the incoming air for proper cylinder combustion. Common causes include Faulty Intake Air Heater (IAH) Relay, Faulty Intake Air Heater, Intake Air Heater Relay harness is open or shorted. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P0540 indicates Intake Air Heater 'A' Circuit.
Common causes: Common causes include Faulty Intake Air Heater (IAH) Relay, Faulty Intake Air Heater, Intake Air Heater Relay harness is open or shorted.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

Save to My Repairs My Repairs

AI answers can be wrong. Verify repairs with testing. Open full chat

Code Popularity 11,126

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jan 19, 2019

Description
Possible Causes
How To Fix
Cost to Diagnose
Comments
Add Comment

💬 Need more help? Ask Coddy for instant answers — it's free!

Code P0540 Description

The Engine Control Module (ECM) uses an Intake Air Heater (IAH) to warm the incoming air for proper cylinder combustion. The ECM grounds the control coil of the IAH relay to energize the heater during cold operation. The control module will command the IAH ON when the engine coolant temperature is below 40 C (104 F). The power to the IAH heater is supplied by the battery positive voltage circuit through the IAH relay.

OBDII Code P0540 - Intake Air Heater 'A' Circuit - AutoCodes.com — P0540 Code - Intake Air Heater 'A' Circuit

What does this mean?

What are the Possible Causes of the DTC P0540?

Faulty Intake Air Heater (IAH) Relay
Faulty Intake Air Heater
Intake Air Heater Relay harness is open or shorted
Intake Air Heater Relay circuit poor electrical connection
Intake Air Heater harness is open or shorted
Intake Air Heater circuit poor electrical connection

How to Fix the DTC P0540?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0540 code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P0540 code?

Need more information on how to fix the P0540 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P0540 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

P0540 Chevrolet — Intake Air Heater 'A' Circuit
P0540 Dodge — Intake Air Heater 'A' Circuit
P0540 Ford — Intake Air Heater 'A' Circuit
P0540 GMC — Intake Air Heater 'A' Circuit

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.