DTC P0011300 – Intake Air Temperature (IAT) Circuit High Input.

P0011300 – Intake Air Temperature (IAT) Circuit High Input

Meaning:
The ECM detects an abnormally high voltage signal from the IAT sensor.
High voltage = very low temperature reading (ECM thinks the air is extremely cold).

1. Common Causes

🌟 Open circuit in IAT sensor wiring (signal wire broken)
🌟 Disconnected IAT sensor connector
🌟 High resistance in signal or ground wire
🌟 Faulty IAT sensor (thermistor open internally)
🌟 Corroded or loose terminals
🌟 MAF sensor issue (when IAT is built into MAF)
🌟 ECM fault (rare)

2. Symptoms

Hard cold start

High idle

Poor fuel economy

Engine may run rich

MIL ON

3. Quick Checks (5 minutes)

Step 1 — Visual Inspection

Check IAT sensor plug for:

Loose connection

Broken locking tab

Oil/dust contamination

Check wiring harness near:

MAF sensor

Air filter box

Intake hose

Step 2 — Clear Code & Wiggle Test

Clear code

Wiggle wiring around the air duct

If code returns → wiring fault

4. Detailed Diagnosis (Workshop Procedure)

A. Check IAT Sensor Resistance (Key OFF)

IAT is a NTC thermistor:

Cold temperature → High resistance

Hot temperature → Low resistance

Temp (°C) Expected Ω

0°C 9–11 kΩ
20°C 2–3 kΩ
40°C 1–1.5 kΩ
80°C 300–400 Ω

If meter shows “OL / infinite resistance” → sensor open → replace IAT.

B. Check Voltage at IAT Connector (Key ON)

Pin-1: 5V reference
Pin-2: Ground

Signal voltage (with sensor unplugged): ≈ 5V (normal)

With sensor connected: 0.5–1.5V (normal depending on temp)

If constant 5V even with sensor connected → wiring open or sensor open.

C. Wiring Continuity Test

Check:

1. Signal wire → ECM pin
2. Ground wire → ECM ground

Look for:

Open circuit

High resistance (>1Ω)

Corrosion at terminals

Repair any wiring issues.

D. ECM Check (Last Option)

If:

Sensor good

Wiring good

Voltage normal

But code still returns → suspect ECM input fault.

5. Repairs

✅ Reconnect loose IAT plug
✅ Replace faulty IAT sensor
✅ Repair/replace damaged wiring
✅ Clean or replace MAF if IAT is built into MAF sensor
✅ Replace ECM (rare)

6. After Repair

Clear code

Road test while monitoring:

IAT vs Ambient Temp

Should be within ± 5°C

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