What it means
The readings from intake air temperature sensors 1 and 2 do not correlate within the calibrated limits. The code does not identify which sensor, if either, is faulty.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Intake air temperature sensors 1 and 2 report the temperature of incoming air at different points or through separate sensing elements, depending on the vehicle. The control module compares their readings for a plausible relationship. P2199 sets when the two readings disagree beyond the calibrated range; it does not specify which sensor or circuit is at fault.
Common causes
Most likely first.
- One IAT sensor drifting
- Wiring issue on one sensor
Symptoms
- Check engine light on
- Hard starting or rough running, especially when cold
- Reduced fuel economy
- Engine performance may be inconsistent
How to diagnose it
- Record freeze-frame data and compare both IAT readings on a scan tool, including whether the engine was cold or warm when the mismatch occurred.
- With the engine cold and off, compare both sensor readings with ambient temperature and each other for an implausible outlier.
- Inspect both IAT sensors and their connectors for poor seating, corrosion, damage, or contamination, and trace their wiring for chafing or breaks.
- Check whether the readings change smoothly as the intake warms, rather than remaining fixed or jumping intermittently.
- Test each sensor circuit and sensor response against the manufacturer’s specification to identify which side of the correlation is inaccurate.
Common fixes
- Reconnect or repair a loose, corroded, or damaged IAT sensor connector.
- Repair damaged wiring in the affected IAT circuit.
- Replace the IAT sensor that fails comparison and circuit tests.
- Clear the code and confirm both readings track plausibly after the repair.
Can I keep driving?
A steady warning light with normal driving is usually not an immediate breakdown risk, but inaccurate air-temperature data can affect cold starting, fueling, and emissions. Avoid relying on the vehicle for demanding trips if it starts poorly or runs inconsistently.
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.