P0099
Intake Air Temperature Sensor 2 Circuit Intermittent/Erratic
- Severity
- Low
- Driving
- Drivable — book it in
The second intake air temperature signal drops out or jumps about. As with any intermittent electrical fault, the cause is far more likely to be a connection than the sensor itself.
Possible causes
- CommonLoose, corroded or backed-out pin in the connector
- CommonChafed wiring that opens only when the engine moves on its mounts
- CommonOil or water that has crept into the connector
- PossiblePoor earth
- PossibleFailing sensor breaking down when hot
What you might notice
- Slight loss of power, particularly on a turbocharged engine
- Hesitation or rough running
- Poor fuel economy
- Check engine light on
- Often nothing obvious while driving
What to check, in order
- Wiggle the connector and flex the harness with live data on screen. An intermittent fault that can be provoked by hand is nearly solved.
- Open the connector and look for corrosion, spread terminals or a pin pushed back out of its housing.
- Check the earth before replacing the sensor.
- Replace the sensor last. Intermittent faults are connections far more often than components, because a component that has failed usually stays failed.
Read this code from your own car
Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.
Where this code sits
P00xxP01xxP02xxP03xxP04xxP05xxP06xxP07xxP08xxP09xxP0AxxP0BxxP0CxxP0DxxP0ExxP0FxxP10xxP11xxP12xxP13xxP14xxP15xxP16xxP17xxP18xxP19xxP1AxxP1BxxP1CxxP1DxxP1ExxP1FxxP20xxP21xxP22xxP23xxP24xxP25xxP26xxP27xxP28xxP29xxP2AxxP2BxxP2CxxP2DxxP2ExxP2FxxP30xxP31xxP32xxP33xxP34xxP35xxP36xxP37xxP38xxP39xxP3AxxP3BxxP3CxxP3DxxP3ExxP3Fxx