AutoCodes – Generic – P166C

P166C Code - Intake Air Heater Resistance

Quick Answer

The Engine Control Module (ECM) monitors the Intake Air (IA) Heater. Common causes include Faulty Intake Air (IA) Heater, Intake Air (IA) Heater harness is open or shorted, Intake Air (IA) Heater circuit poor electrical connection. 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: P166C indicates Intake Air Heater Resistance.
Common causes: Common causes include Faulty Intake Air (IA) Heater, Intake Air (IA) Heater harness is open or shorted, Intake Air (IA) Heater circuit poor electrical connection.
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.

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Code Popularity 4,550

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 06, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P166C Description

The Engine Control Module (ECM) monitors the Intake Air (IA) Heater. The ECM sets the OBDII code when the Intake Air (IA) Heater is not to factory specifications.

OBDII Code P166C - Intake Air Heater Resistance - AutoCodes.com — P166C Code - Intake Air Heater Resistance

What does this mean?

What are the Possible Causes of the DTC P166C?

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

How to Fix the DTC P166C?

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 P166C 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 P166C code?

Need more information on how to fix the P166C code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P166C code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

P166C Buick — Intake Air Heater Resistance
P166C Cadillac — Intake Air Heater Resistance
P166C Chevrolet — Intake Air Heater Resistance
P166C GMC — Intake Air Heater Resistance

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.

Frequently Asked Questions about P166C Code

1. What does the OBDII code P166C mean?

The P166C code indicates an issue with the intake air heater circuit, specifically related to abnormal resistance levels detected by the engine control module (ECM).

2. What are the common symptoms of the P166C code?

Common symptoms include difficulty starting the engine in cold weather, poor engine performance, increased emissions, and an illuminated check engine light.

3. What causes the P166C code to appear?

The most common causes are a faulty intake air heater, damaged wiring or connectors in the heater circuit, excessive resistance in the heater element, or a failing ECM.

4. Can I drive with the P166C code active?

While you can drive with this code, it is not recommended, especially in cold conditions, as it may cause starting issues and negatively affect engine performance.

5. How can I diagnose the P166C code?

Start by inspecting the intake air heater, wiring, and connectors for damage or corrosion. Use a multimeter to check the resistance of the heater element and compare it to manufacturer specifications.

6. What tools are needed to repair the P166C code?

You may need a multimeter, basic hand tools, a diagnostic scan tool, and possibly a replacement intake air heater or related components.

7. How do I fix the P166C code?

Repairs may include replacing the intake air heater, repairing damaged wiring or connectors, clearing debris from the heater element, or reprogramming the ECM if needed.

8. How much does it cost to fix the P166C code?

The repair cost varies depending on the issue, but replacing the intake air heater typically costs $100 to $300, including parts and labor.

9. Can a dirty air filter trigger the P166C code?

No, a dirty air filter is not directly related to this code, as P166C specifically pertains to the intake air heater circuit.

10. How do I prevent the P166C code from recurring?

Regularly inspect and maintain the intake air heater, wiring, and connectors, especially in areas with extreme cold. Address any electrical issues promptly.