P0099
Intake Air Temperature Sensor 2 Circuit Intermittent/Erratic Bank 1
Fuel & air metering
Generic OBD-II
Low
What it means
P0099 means the signal from the second intake air temperature sensor on bank 1 is cutting out or jumping around rather than reading steadily. It's usually a loose connector or chafed wire. The reading feeds fine fuel and timing adjustments, so the engine keeps running while the code is set.
Low
Can I keep driving? Usually drivable — the engine runs, with at most occasional rough idle or hesitation when the signal drops out, until it's fixed.
Common symptoms
What you'll notice
- Check-engine light on, sometimes intermittently
- Intake air temperature 2 reading fluctuates or drops out
- Occasional rough idle or hesitation
- Slightly inconsistent fuel economy
Common causes
Most likely first
- Loose or corroded connector at the intake air temperature sensor 2Likely
- Damaged or worn-out sensor wiring that shorts intermittentlyCommon
- Faulty or failing intake air temperature sensor 2Common
- Environmental factors such as heat or moisture affecting the connectionLess often
- Intermittent fault in the engine control module (ECM) — rareLess often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and watch the live IAT 2 signal for dropouts.
- Inspect and clean the sensor connector; do a wiggle test to catch the intermittent fault.
- Check the wiring for chafing, breaks, or moisture intrusion and repair as needed.
- Measure the sensor's resistance against a temperature chart and replace if erratic.
- Monitor live data over time to confirm the repair; consider the ECM last. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0099?+
Usually yes. The engine keeps running; the fault is intermittent and mostly affects fine air/fuel adjustments, so fix it at your convenience.
Can I just clear P0099?+
Because it's intermittent it will return until the loose connection, wiring, or sensor is repaired.
Related codes
Often seen with P0099
Read & clear P0099 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX