P0099
UniversalIntake Air Temperature Sensor 2 Circuit Intermittent/Erratic
Medium SeverityThis code indicates that the vehicle's computer (PCM) is receiving inconsistent or unreliable data from the Intake Air Temperature Sensor 2 circuit. This typically means the sensor's readings are fluctuating erratically, which can lead to the PCM miscalculating engine fuel and ignition timing.
⚠️ Before You Begin (Safety First)
Always allow the engine to cool before working on it to prevent burns. Disconnect the battery's negative terminal before performing any electrical repairs to prevent accidental shorts or injury. Use appropriate personal protective equipment, such as gloves and eye protection.
Common Symptoms
- Check Engine Light illuminated
- Reduced fuel economy
- Rough idling
- Lack of engine power
- Poor acceleration
- Engine hesitation or stumbling
Common Causes
- Faulty Intake Air Temperature Sensor 2
- Corroded or loose electrical connectors for the IAT Sensor 2
- Damaged or frayed wiring in the IAT Sensor 2 circuit
- Intermittent short or open in the sensor circuit
- Less commonly, a faulty Powertrain Control Module (PCM)
Frequently reported on: General/Universal (vehicles with forced induction or complex intake systems), Ford F-150 EcoBoost (2015-2020), Subaru WRX/STI (2010-2018), Chevrolet Silverado (2014-2019) with specific engine configurations
Diagnostic Steps
- Locate the Intake Air Temperature Sensor 2 (often found in the intake manifold, air ducting after a turbo/supercharger, or intercooler pipe).
- Inspect the sensor's electrical connector and wiring for any signs of damage, corrosion, or looseness.
- Using a multimeter, test the sensor's resistance at various temperatures (if possible) and check for proper voltage reference and ground at the connector (refer to vehicle-specific repair manual).
- If the sensor tests faulty or shows intermittent readings, disconnect the old sensor and replace it with a new, OEM-equivalent part.
- Clear the trouble code using an OBD-II scanner and test drive the vehicle to confirm the repair.
👨🔧 When to Call a Professional
While replacing the Intake Air Temperature Sensor 2 is often straightforward, if the code persists or is accompanied by other drivability issues after sensor replacement, it strongly suggests a more complex underlying wiring or PCM issue. Consult a professional mechanic for advanced diagnostics to avoid further damage.
Commonly Asked Questions
What is an Intake Air Temperature Sensor 2?
An Intake Air Temperature Sensor 2 measures the temperature of the air entering the engine, often located after a turbocharger or intercooler. This data helps the PCM calculate optimal fuel delivery and ignition timing.
Can I drive with a P0099 code?
While it might not cause immediate breakdown, driving with a P0099 can lead to reduced fuel economy, decreased engine performance, and potentially increase emissions. It's recommended to address it promptly to prevent further issues.
How do I locate the Intake Air Temperature Sensor 2?
The location of IAT Sensor 2 varies by vehicle but is typically found in the intake manifold, air intake tube after a turbocharger/supercharger, or in the intercooler piping. Consult your vehicle's service manual for the exact location.
Is it possible for a dirty air filter to cause a P0099 code?
A dirty air filter itself is unlikely to directly cause an IAT Sensor 2 circuit error (P0099). However, extremely restricted airflow might indirectly affect sensor readings in some cases, but the primary suspects are the sensor or its wiring.
Do I need special tools to replace the sensor?
Replacing the Intake Air Temperature Sensor 2 typically only requires basic hand tools like wrenches or sockets, and possibly a flathead screwdriver or trim removal tool for connector clips. A multimeter is helpful for diagnosis.