P0099: Intake Air Temperature Sensor 2 Circuit Intermittent/Erratic Bank 1
What to do
Usually driveable. Mention that the fault comes and goes, as that changes how it should be tested.
What this code means
The second intake air temperature signal is unstable rather than steadily wrong. Intermittent faults on charge-pipe sensors are usually mechanical in origin — a connector shaken loose by boost pressure pulsing through the pipework, or a wire fractured inside intact insulation. Watching live data during a road test finds these far more reliably than static testing does.
Likely causes
Start here
- Intermittent wiring fault · moderate
- Corroded or loose connector · easy
Less common
- Chafed harness against engine or bracket · moderate
- Faulty intake air temperature sensor · easy
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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