AutoCodes – Generic – P0099

P0099 Code - Intake Air Temperature Sensor 2 Circuit Intermittent

Quick Answer

The Intake Air Temperature (IAT) sensor 1 is a variable resistor that changes the voltage on the Engine Control Module (ECM) supplied 5 V signal circuit. Common causes include Faulty Intake Air Temperature (IAT) sensor, Intake Air Temperature sensor harness is open or shorted, Intake Air Temperature sensor 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: P0099 indicates Intake Air Temperature Sensor 2 Circuit Intermittent.
Common causes: Common causes include Faulty Intake Air Temperature (IAT) sensor, Intake Air Temperature sensor harness is open or shorted, Intake Air Temperature sensor 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 14,154

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on May 16, 2022

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0099 Description

The Intake Air Temperature (IAT) sensor 1 is a variable resistor that changes the voltage on the Engine Control Module (ECM) supplied 5 V signal circuit. The signal varies with inlet air temperature in the sensor bore and is displayed by the scan tool as °C (°F). The IAT sensor 2 and the humidity sensor share the same circuit. The IAT sensor 2 signal is displayed by the scan tool as Hertz (Hz) and °C (°F). The Diagnostic Trouble Code (DTC) will be set when the ECM detects that the IAT sensor 2 signal is intermittent or has abruptly changed for longer than 5 s.

OBDII Code P0099 - Intake Air Temperature Sensor 2 Circuit Intermittent - AutoCodes.com — P0099 Code - Intake Air Temperature Sensor 2 Circuit Intermittent

What does this mean?

What are the Possible Causes of the DTC P0099?

Faulty Intake Air Temperature (IAT) sensor
Intake Air Temperature sensor harness is open or shorted
Intake Air Temperature sensor circuit poor electrical connection
Faulty Engine Control Module (ECM)

How to Fix the DTC P0099?

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 does this mean?

Code Tech Notes

The Intake Air Temperature (IAT) sensor 1, IAT sensor 2, Humidity sensor, MAF sensor, and BARO pressure sensor are integrated within the Mass Air Flow / Multifunction Intake Air Sensor.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0099 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 P0099 code?

Need more information on how to fix the P0099 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P0099 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

P0099 Buick — Intake Air Temperature Sensor 2 Circuit Intermittent
P0099 Cadillac — Intake Air Temperature Sensor 2 Circuit Intermittent
P0099 Chevrolet — Intake Air Temperature Sensor 2 Circuit Intermittent
P0099 GMC — Intake Air Temperature Sensor 2 Circuit Intermittent

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 P0099 Code

1. What are the common symptoms of OBDII code P0099 (Intake Air Temperature Sensor 2 Circuit Intermittent)?

- Common symptoms include rough idling, poor engine performance, decreased fuel efficiency, and potential stalling.

2. What can cause the OBDII code P0099 to appear?

- The code may be triggered by a faulty intake air temperature sensor, wiring issues, poor connections, or a problem with the sensor circuit.

3. How can I diagnose the cause of OBDII code P0099?

- You can start by visually inspecting the sensor and its wiring for any damage. Using a multimeter, test the sensor's resistance and voltage readings to determine if it is functioning properly.

4. Can a dirty air filter trigger OBDII code P0099?

- Yes, a dirty air filter can disrupt the intake air temperature readings, potentially leading to the intermittent circuit issue and triggering the code.

5. Is it safe to continue driving with OBDII code P0099 present?

- It is not recommended to drive with the code active, as it can lead to poor engine performance and fuel efficiency, potentially causing further damage over time.

6. How can I repair OBDII code P0099?

- Repair options include replacing the intake air temperature sensor, repairing any damaged wiring or connections, cleaning the sensor, and ensuring proper installation.

7. Can a DIY enthusiast fix OBDII code P0099?

- Depending on your mechanical skills and access to tools, DIY enthusiasts can attempt to diagnose and repair the issue themselves, but it is advisable to seek professional help if unsure.

8. Will resetting the OBDII system clear the P0099 code?

- Resetting the system may temporarily clear the code, but it is important to address the underlying issue causing the code to prevent it from reoccurring.

9. How much does it cost to repair OBDII code P0099 at a mechanic?

- The cost of repair can vary depending on the exact cause of the issue, but it generally ranges from $100 to $300, including parts and labor.

10. Are there any preventive measures to avoid OBDII code P0099 in the future?

- Regularly inspecting and maintaining the intake air temperature sensor, ensuring proper air filter maintenance, and addressing any wiring issues promptly can help prevent the recurrence of the code.