DTC P0070 — Ambient Air Temperature (AAT) Sensor Circuit.

✅ P0070 – Ambient Air Temperature Sensor Circuit

🔍 Meaning

The ECM/PCM detects a fault in the ambient air temperature sensor circuit — either open, shorted, or out of range.

The sensor is typically a 2-wire NTC thermistor:

Resistance decreases when temperature increases

Resistance increases when temperature drops

🚗 Common Symptoms

Incorrect outside temperature reading on instrument cluster

AC/Climate control performance issues

AC compressor not engaging on some models

Engine cooling fans running unusually

DTC stored, MIL may or may not illuminate

🔧 Probable Causes

1. Faulty ambient air temperature (AAT) sensor

2. Open or short circuit in wiring

3. Corroded/loose connector, often due to bumper area water exposure

4. Damage due to accidents, rodents, or road debris

5. Faulty ECM/PCM (rare)

🧰 Step-by-Step Diagnostic Procedure

1️⃣ Visual Inspection

Locate the AAT sensor (usually in front bumper, grille, or radiator support)

Check for:

Broken sensor

Damaged harness

Corrosion in connector

Moisture/water entry

Wiring pulled due to accident/repair

2️⃣ Check Live Data

Using OBD scanner, check Ambient Air Temperature value.

If reading is abnormal (e.g., –40°C or +150°C):

–40°C = Open circuit

+150°C = Short to ground

This tells you where the problem is.

3️⃣ Sensor Resistance Test

Unplug the sensor → measure resistance.

Typical NTC sensor values:

~30–50 kΩ at –20°C

~9–10 kΩ at 20°C

~2–3 kΩ at 50°C

If resistance is:

Infinite → sensor open

0–1Ω → sensor shorted
Then the sensor is faulty.

4️⃣ Wiring Test

With connector unplugged:

Check 5V reference or signal voltage (varies by car, often ~5V)

Check ground continuity

Wiggle harness to see intermittent faults

If:

No reference voltage → wiring/ECM issue
Poor ground → fix GND point

5️⃣ Substitute Test

If possible:

Plug in a known-good sensor
(or use a resistor of approx. 10kΩ to simulate ~20°C)

If temperature reading becomes normal → original sensor faulty.

🔧 Common Fixes

🌟 Replace ambient air temp sensor
🌟 Repair or replace damaged wiring
🌟 Clean or replace corroded connectors
🌟 Secure wiring away from radiator fan & bumper area
🌟 Clear codes and retest

Welcome To Madurai Car Service 💐🙏.