🔧 P1111 ISUZU Code – Intake Air Temperature (IAT) Sensor Problem
📌 Meaning of P1111 Code
The P1111 code is defined when the Powertrain Control Module (PCM) detects a signal voltage outside the normal range from the Intake Air Temperature (IAT) sensor.
The IAT sensor is a thermistor, a semiconductor device that changes its resistance based on the air temperature.
It is installed in the intake passage of the engine air system and consists of:
- a signal circuit (powered at ~5V by the PCM)
- a ground circuit
⚠️ Possible Symptoms
- Engine light on (Check Engine)
- No noticeable symptoms in some cases
📍 Possible Causes of P1111 ISUZU Code
- 🔧 Faulty IAT sensor
- 🔌 Open or shorted sensor wiring harness
- ⚡ Poor electrical connection in the sensor circuit
🧰 How to Fix P1111 ISUZU Code?
- Visually inspect the IAT sensor and its connections
- Check the wiring harness: look for cuts, burns, or damaged sections
- Examine the connectors:
- Bent, broken, or corroded pins
- Pushed back or improperly inserted pins
- Test the sensor resistance with a multimeter (according to ambient temperature)
- Replace the sensor if values are out of specification
🔬 IAT Sensor Operation
| Air Temperature | Thermistor Resistance | Voltage Measured by PCM |
|---|---|---|
| Cold Air | High | High Voltage |
| Hot Air | Low | Low Voltage |
The PCM interprets these voltage variations to determine the actual temperature of the air entering the engine.