What it means
The Intake Air Temperature Sensor 2 circuit signal for Bank 1 is intermittent or erratic.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Intake Air Temperature Sensor 2 measures intake-air temperature at a second sensing point, which varies by vehicle. The control module sets P0099 when this sensor's signal jumps, drops out, or otherwise changes erratically, often because vibration interrupts a connector or wire contact.
Common causes
Most likely first.
- Connector loose or corroded
- Connector with intermittent contact under vibration
- Harness routed against vibrating component
Symptoms
- Check engine light on
- Intermittent rough running or hesitation
- Poor fuel economy
How to diagnose it
- Check freeze-frame data and graph live Sensor 2 temperature to see whether it jumps or drops out as the fault occurs.
- Inspect Sensor 2's connector for looseness, corrosion, damaged terminals, or a latch that does not hold the plug securely.
- Trace the Sensor 2 harness for chafing or routing against a vibrating or moving component.
- With live data displayed, gently move the accessible connector and harness to check for signal changes, keeping clear of moving and hot parts.
- If the signal still behaves erratically, test the Sensor 2 circuit and sensor response to the manufacturer's specification.
Common fixes
- Secure the Sensor 2 connector and repair its latch or terminal fit.
- Clean or replace corroded or damaged connector terminals.
- Repair and reroute chafed Sensor 2 wiring away from vibration or moving parts.
- Replace Intake Air Temperature Sensor 2 if testing confirms intermittent sensor failure.
Can I keep driving?
If the engine runs normally, short local trips are usually manageable, but intermittent readings can cause unpredictable hesitation or rough running. Stop driving if the engine begins to stall or loses power in traffic.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.