You can keep driving with P0070. The main effects are a wrong outside-temperature display and possibly quirky automatic climate control; the engine and transmission usually run fine. Repair it at your convenience. P0070 means the powertrain control module (PCM) has found a general electrical fault in the circuit for the ambient (outside) air temperature sensor — an open, a short, or a reading that is electrically impossible. It is the master "circuit" code for that sensor, sitting above the more specific range/performance (P0071), low (P0072), and high (P0073) siblings.
What P0070 means
The ambient air temperature (AAT) sensor is a negative-temperature-coefficient (NTC) thermistor: its resistance falls as it warms and climbs as it cools. It sits in a voltage-divider network fed by a low reference voltage, so the changing sensor resistance changes the voltage the PCM reads on the signal line — and the module converts that voltage into an outside-air temperature. On most vehicles the AAT sensor lives behind the front grille or bumper and is shared with the instrument cluster and the automatic climate-control system, and the PCM broadcasts the reading to the other modules over the CAN bus. P0070 is the general circuit member of the family: the PCM sets it when the signal voltage is stuck at a rail or otherwise out of the plausible window in a way that points to a wiring or connector problem rather than a specific low or high value. It is distinct from P0071 (range/performance — the signal is present but drifted or implausible versus other temperatures), P0072 (circuit low — signal shorted low, usually a short to ground), and P0073 (circuit high — signal high or open, such as a disconnected sensor).
Symptoms
- Check-engine (MIL) light on with P0070 stored, often alongside P0071/P0072/P0073
- Outside-temperature display on the dash or infotainment reads wildly wrong, stuck, or shows dashes
- Automatic climate control behaves oddly — wrong fan or temperature blending, or it won't reach set temperature
- On vehicles that use ambient temperature in transmission or emissions strategy, slightly altered shift feel or cold-start behavior
- No obvious drivability change on many vehicles — the code is often found only because the temperature display is wrong
Common causes
- Open, chafed, or broken wire in the AAT signal or signal-return (SIGRTN/ground) circuit — the most common cause of a general circuit fault
- Corroded, loose, or water-intruded AAT sensor connector, common because the sensor sits in the exposed front-of-vehicle airflow
- Failed AAT sensor thermistor (open or shorted internally)
- Short to ground or short to voltage in the signal wire, dragging the reading to a rail
- Damaged or poorly seated PCM connector on the AAT signal/return pins
- Rodent or impact damage to the harness near the grille, bumper, or condenser where the sensor mounts
- PCM internal fault on the AAT input (uncommon — confirm wiring, connector, and sensor first)
Severity & driving advice
Severity: Low — Mostly a comfort and display fault — the engine runs and drives normally, but auto-climate and the outside-temp readout can misbehave.
Can I drive? You can keep driving with P0070. The main effects are a wrong outside-temperature display and possibly quirky automatic climate control; the engine and transmission usually run fine. Repair it at your convenience.
Diagnostic approach
- Scan codes and read freeze-frame — Confirm P0070 and note any companion codes. If P0071, P0072, or P0073 are stored with it, they tell you whether the fault leans toward range/performance, low (short to ground), or high (open) — which shortens the wiring test. Record the ambient temperature the PCM reports and compare it to a known thermometer; a reading far from reality (or pinned at a limit) confirms the concern.
- Compare temperature sensors with the scan tool — With the vehicle cold after an overnight soak, view the AAT, intake-air (IAT), and engine-coolant (ECT) PIDs together. On a truly cold engine all three should read close to the real ambient temperature; an AAT that is stuck near the high or low end of its range while IAT and ECT agree points at the AAT circuit, not the weather.
- Inspect the sensor, connector, and harness — Locate the AAT sensor (typically behind the grille or front bumper, near the condenser) and inspect it for impact damage and debris. Check the connector for corrosion, spread or backed-out pins, and moisture, and wiggle-test the harness while watching the live temperature value to expose an intermittent open.
- Check the signal and return circuits for an open — With the ignition off and the sensor and PCM disconnected, measure resistance end-to-end on both the AAT signal wire and the signal-return (SIGRTN) wire. Good continuity reads very low — on the order of under 5 ohms; a high or infinite reading confirms an open in that leg, which typically drives the high/P0073 side of the family.
- Check the signal circuit for a short to ground or voltage — Still isolated, measure from the AAT signal wire to a good ground: a healthy, un-shorted circuit reads high, on the order of over 10K ohms. A near-zero reading is a short to ground (drives the low/P0072 side). Then, key on, confirm the signal line is not being pulled up by a short to another voltage source.
- Bench-test the AAT sensor thermistor — With the sensor unplugged, measure its resistance and watch it change with temperature — resistance should fall as you warm the sensor (for example with a hand or a heat source) and rise as it cools, since it is an NTC device (typically a few thousand ohms near room temperature). A reading that is open, shorted, or does not track temperature means the sensor is bad.
- Repair, clear, and confirm — Fix the open, short, connector, or sensor you found. Clear the codes and confirm the reported ambient temperature now matches a real thermometer with the vehicle cold, and that the climate display and auto-climate behave normally. Re-run the PCM self-test and road-test to verify P0070 and its siblings stay off.
FAQ
Is it safe to drive with a P0070 code?
Generally yes. P0070 is a low-severity circuit fault in the outside-air temperature sensor, so the engine and transmission normally run and drive without issue. The visible effects are a wrong or stuck outside-temperature display and sometimes odd automatic climate-control behavior. Because a few vehicles use ambient temperature in cold-start or shift strategy, it is still worth fixing, but it is not an emergency.
What is the difference between P0070, P0071, P0072, and P0073?
They all cover the same ambient air temperature sensor circuit but describe different failure modes. P0070 is the general circuit fault. P0071 is range/performance — the signal is present but implausible compared with other temperatures. P0072 is circuit low, usually a short to ground pulling the signal down. P0073 is circuit high, typically an open circuit or a disconnected sensor. If P0070 is stored with one of the others, that sibling narrows down the exact wiring test.
Where is the ambient air temperature sensor located?
On most vehicles the AAT sensor is mounted in the front of the vehicle in the incoming airflow — behind the grille, in front of the radiator/condenser, or in the front bumper — so it reads true outside air rather than under-hood heat. On some models it is integrated into an exterior mirror. Because it sits in the weather, its connector and pigtail are common corrosion and impact points.
Can a bad sensor cause a wrong temperature display but no check-engine light?
Yes. The same AAT sensor feeds both the PCM and the instrument-cluster/climate display, and the PCM shares the reading over the vehicle network. A drifted-but-still-plausible sensor can show a wrong outside temperature without tripping a hard circuit code, while an open or short is what usually sets P0070 or its siblings. Comparing the AAT reading against the coolant and intake-air temperatures on a cold engine helps confirm the sensor is at fault.
Will P0070 make my car fail an emissions test?
P0070 turns on the check-engine light, and an illuminated MIL alone will fail most OBD-II emissions inspections even though this particular fault has little effect on tailpipe output. Diagnose and repair the circuit, clear the code, and let the readiness monitors reset before testing so the light stays off.