P0070
Ambient Air Temperature Sensor CircuitP0070 is a generic OBD-II powertrain diagnostic trouble code: Ambient Air Temperature Sensor Circuit. It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0070 means
P0070 indicates that the PCM has detected a signal from the ambient air temperature (AAT) sensor circuit that is out of the expected range or implausible. The AAT sensor is a simple negative-temperature-coefficient (NTC) thermistor typically mounted behind the front grille or in the front bumper area, measuring the temperature of outside air flowing across the vehicle.
The PCM uses AAT data to assist with cold-start fuel enrichment, climate control logic, and to cross-check intake air temperature readings. On vehicles with an automatic climate system, the body control module also reads AAT to maintain set cabin temperature. When the circuit voltage falls outside calibrated limits — due to a failed sensor, corroded connector, or wiring fault — the PCM sets P0070.
Because AAT is a supplementary input rather than a primary fuelling signal, P0070 rarely causes drivability problems. The most noticeable effects are an incorrect or missing outside temperature display on the dashboard and reduced efficiency of automatic climate control. Fuel economy impact is minor and only felt during very cold starts when the PCM falls back to a default temperature assumption.
Common causes
Most-frequently reported root causes when P0070 is logged.
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1
Failed AAT sensor (most common — the sensor is exposed to road debris, moisture, and temperature extremes).
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2
Corrosion or water intrusion at the sensor connector, increasing circuit resistance.
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3
Open or short in the wiring between the sensor and the PCM.
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4
Damaged connector terminals caused by road spray or stone impact.
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5
PCM input circuit fault (rare).
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6
Sensor contaminated with road film or ice, skewing its thermal response.
Symptoms drivers notice
How to diagnose P0070
A typical diagnostic flow when this code is present.
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1
Record freeze frame data and all stored codes; check for co-existing codes that could share wiring (e.g. HVAC-related fault codes).
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2
Locate the AAT sensor (typically behind the front grille) and visually inspect for physical damage, connector corrosion, or moisture ingress.
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3
With the connector unplugged, measure sensor resistance and compare to the temperature-resistance chart in the service manual; at typical ambient temperatures the sensor should read a few kilohms.
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4
Check reference voltage (usually 5 V) and ground at the harness connector side with the ignition on.
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5
Inspect wiring continuity from sensor connector back to the PCM for opens or shorts to ground/power.
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6
If sensor resistance is out of range or the connector shows heavy corrosion, replace the sensor and clean or replace the connector.
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7
Clear codes, allow a complete drive cycle, and verify the fault does not return.
Related powertrain codes
Frequently asked questions
Does P0070 cause the car to run poorly?
Generally no. The AAT sensor is a supplementary input. The PCM substitutes a default value when the signal is absent, so fuelling and ignition timing are largely unaffected. The most common complaint is an incorrect outside temperature reading on the dashboard.
Where is the AAT sensor located?
Most vehicles mount it behind the front grille or inside the front bumper fascia so it measures ambient air flow. Some vehicles integrate it into the HVAC inlet or the outside mirror housing. Check the vehicle-specific service manual to locate it accurately.
Can corrosion alone cause this code without the sensor failing?
Yes. The AAT sensor is exposed to water, salt, and road debris, and connector pin corrosion is the most common root cause. Cleaning the connector with electrical contact cleaner and applying dielectric grease often resolves the code before sensor replacement is needed.
Will the code clear on its own if the fault is intermittent?
The MIL will extinguish after several consecutive drive cycles without the fault being detected, but the code remains in pending history. If the connector has intermittent corrosion, the code will recur. Address the root cause rather than waiting for self-clearing.
Disabling P0070 in software
RaceTune can permanently disable P0070 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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