P009A: Intake Air Temperature/Ambient Air Temperature Correlation

What does P009A mean?

After a long standstill with the engine cold, intake air temperature and ambient air temperature should be about the same. P009A is set when the two sensors disagree by more than a threshold at the next start. A detected engine block heater usually suspends the test. Several manufacturers perform this comparison under other codes; no manufacturer description naming P009A itself was found. Suspects are both sensors, an ambient sensor in a heat-affected position and contact resistance at a connector.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Check engine light on
• Usually no noticeable symptoms

Common causes

• High Intake air temperature sensor drifting or contaminated
• Medium Ambient temperature sensor faulty or in a heat-affected position
• Medium Contact resistance at a connector
• Low Engine block heater or auxiliary heater distorting the comparison

Likelihood is a general estimate across vehicles; your make and model may differ.