P0097 Low Input of IAT Sensor 2 Circuit

What is the P0097 code?

The P0097 error code is a generic OBD-II code related to the powertrain. It indicates a low input from the Intake Air Temperature (IAT) Sensor 2 circuit. Although generic, diagnostic procedures can vary depending on the vehicle’s make and model.

Role of the IAT Sensor

The IAT (Intake Air Temperature) sensor measures the temperature of the air entering the engine. This data is crucial for the Powertrain Control Module (PCM), as it influences ignition timing, the air-fuel mixture, and emission control. High air temperature increases combustion temperatures and nitrogen oxide (NOx) emissions.

The sensor operates with a thermistor. The PCM sends it a 5-volt reference voltage. The thermistor’s resistance varies with temperature: it is high when the air is cold and low when the air is hot. This variation changes the voltage signal sent back to the PCM. The P0097 code is triggered when the PCM detects an abnormally low temperature (or an abnormally high voltage) from the IAT sensor 2 circuit.

Symptoms of the P0097 Code

• The engine warning light (MIL) illuminates on the dashboard.
• Decreased engine performance or rough idle.
• Increased fuel consumption.
• Failure in the emissions test (high NOx emissions).
• In some cases, no noticeable symptoms other than the warning light are present.

Possible Causes of the Fault

• Faulty IAT Sensor 2 (most common internal failure).
• Wiring issue: short to ground on the signal circuit, open wire, damaged or corroded connector.
• Lack of reference voltage (5V) or ground at the sensor.
• Rare PCM failure itself.

Diagnosis and Solutions

Step 1: Data Reading
Using an OBD2 scanner, check the live data from the IAT sensor 2. On a cold engine, the indicated temperature should be close to the ambient temperature and the Engine Coolant Temperature (ECT) sensor reading.

Step 2: Sensor Test
If the reading is abnormally low (e.g., -40°C), disconnect the IAT sensor connector. The scanner reading should now drop to its minimum value. If this happens, the IAT sensor is very likely faulty and needs to be replaced.

Step 3: Circuit Test
If the reading remains abnormally low even after disconnecting the sensor, the problem lies in the circuit. Use a multimeter to:
– Check for continuity and the absence of a short to ground on the signal wire.
– Verify the presence of the 5V reference voltage and ground at the sensor connector (ignition on).

Step 4: Repair
Repair or replace any damaged wiring. If all wiring is intact and the voltages are correct, a PCM failure, although rare, is possible.

Related Codes

DTC codes related to IAT sensors: P0095, P0096, P0098, P0099, P0110, P0111, P0112, P0113.