P0099: Intake Air Temperature Sensor 2 Circuit Intermittent/Erratic Bank 1 — what it means, the affected system and what to check before replacing parts.
Meaning, symptoms, causes and checks
P0099 means intake-air-temperature sensor 2 on bank 1 has an intermittent or erratic electrical signal. Check for intermittent contact, wiring faults and changing live-data readings before replacing the sensor.
Affected system: Intake air temperature sensing
Symptoms
- Check Engine light
- Unstable or implausible scan data
- Poor idle, acceleration, or fuel economy
- Intermittent behavior as temperature or wiring position changes
Possible causes
- Loose pins, corrosion, damaged wiring, or poor ground
- Missing reference voltage or short to power or ground
- Contaminated, biased, or failed sensor
- Air, exhaust, or mechanical condition affecting the reading
What to check
- Save codes and freeze-frame data
- Check the value during engine-off, cold-start, and warm operation
- Inspect wiring and connectors
- Test voltage, ground, signal, and continuity to specification
- Verify a smooth plausible reading after repair
- Inspect the connector and harness before replacing the sensor
- Verify reference voltage, ground, signal, and heater supply
- Compare the reading with related sensors
Also written as: P0099-00, P009900, PO099 (some scan tools add the fault-type byte, e.g. -00).