P0070 — Problem with outside air temperature sensor circuit

The code indicates a problem with the ambient air temperature sensor or its wiring. This sensor measures outside air temperature to help the engine control system adjust fuel mixture and other settings. The code appears when the sensor signal is missing, erratic, or out of expected range.

Common causes

The cause is almost always one of a few things. Here they are — P0070 rarely comes from anything outside this list:

• Faulty ambient air temperature sensor
• Damaged or corroded wiring/connectors
• Poor sensor grounding
• Sensor contamination or blockage
• Faulty engine control module (rare)

Where to start

In the order a sensible mechanic would work — the cheap checks first, the expensive replacements only after:

1. Inspect and clean sensor and connectors
2. Check wiring for damage or corrosion
3. Test sensor resistance and replace if faulty
4. Repair or replace wiring as needed
5. Replace sensor if all else fails

That is what holds for P0070 in general. From here it depends on your engine — tell me which car it is and what it does, and I will give you the steps for it: real procedures, torque figures and diagrams instead of general advice.