Intake Air Heater (IAH) 1 Circuit High
The intake air heater circuit has detected high voltage.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The system that heats the air going into the engine to help it start is seeing too much voltage, which can cause it to not work properly.
What the computer is actually seeing
The engine control module (ECM) senses an intake air heater voltage over the threshold, often above 5 volts when it shouldn't be.
What a healthy reading looks like
Intake air heater voltage should be between 0.0 and 5.0 Volts during operation; at idle, it should typically be below 1.5 Volts.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Inspect the intake air heater circuit wiring and connectors for damage or corrosion. If found, repair or replace as needed. Decision: Repair/replace wiring or connectors?
- 22. Measure the voltage at the intake air heater connector with the ignition on and engine off. Expected: 0.0 to 5.0 Volts. If over 5 Volts, the circuit may be shorted. Decision: If voltage is too high, go to step 3, if normal go to step 4.
- 33. Inspect for shorts to power in the intake air heater circuit. Fix any shorts found. Decision: Did you find a short?
- 44. Test the intake air heater with a multimeter to check resistance. Expected: Typically between 5 to 10 ohms. If out of spec, replace the intake air heater. Decision: Is the resistance within spec?
- 55. If all previous steps are normal, consider the ECM failing and require replacement after verifying other issues are ruled out.
Common causes
- Faulty intake air heater
- Short in wiring harness
- Corroded connectors
- Faulty ECM
Typical repair cost
$$
Related codes
Frequently asked questions
Can I still drive the vehicle with this code?
Yes, but expect cold start issues and potential rough running until the problem is fixed.
Will this code come back after clearing?
It may return if the underlying issue isn't resolved. Repeated codes indicate a persistent problem.
Why does this code pair with others?
It often reflects multiple issues related to the intake air heater and other performance-related components in the system.
Working a real vehicle right now?
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