P0074: Ambient Air Temperature Sensor Circuit A Intermittent/Erratic

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. P0074 is set when the signal jumps or is noisy, i.e. changes faster than a real temperature can, which typically points to a loose contact.

Low severity. Can I keep driving?Yes, you can normally keep driving and take it to a repair shop when convenient.

Symptoms

Outside temperature display jumps
Climate control regulates incorrectly
Check engine light on (manufacturer-dependent)
Other monitors may not complete

Most likely causes

Loose contact or corrosion at the connector
Wire broken inside the harness
Sensor faulty

What to check, in order

Start with the simplest. You can tick off each step.

With the engine cold, compare the reading with the outside temperature
Gently move the wiring with the engine running and watch whether the reading changes.
Check the connector
Measure the sensor's resistance against the manufacturer's specification
Check power and ground before replacing it

Good to know

Repair difficulty: easy
It affects emissions.

What each character of P0074 means

P: Powertrain: engine and transmission
0: Generic code: same on every make
0: Subsystem depends on the code range
74: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0074?

Yes, you can normally keep driving and take it to a repair shop when convenient.

What causes code P0074?

The most common causes are: loose contact or corrosion at the connector; wire broken inside the harness; sensor faulty.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.