P0070: Ambient Air Temperature Sensor Circuit A

What does P0070 mean?

The ambient air temperature sensor A is an NTC thermistor whose resistance falls as temperature rises. Its value is used by the climate control, the outside temperature display and the engine control module, which needs it to enable other diagnostics and to correct its maps. Depending on the vehicle the engine control module reads the sensor directly, or the instrument cluster or another module sends the value over the data bus; some vehicles have no sensor and estimate ambient temperature from intake air temperature. P0070 is the general circuit fault or an invalid signal, for example when the instrument cluster reports the value as invalid or the reading is implausibly low.

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

Symptoms

• Wrong or missing outside temperature display
• Climate control regulates incorrectly
• Check engine light on (manufacturer-dependent)
• Other monitors may not complete

Common causes

• High Sensor faulty (exposed to spray and stone chips at the front)
• High Connector corroded or wire damaged, e.g. after front-end damage
• Medium Instrument cluster or data transmission faulty (vehicles with bus-supplied value)
• Low Engine control module faulty

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