P0113 — Intake Air Temperature (IAT) Sensor 1 Circuit High

Category

Powertrain → Sensors (Air/Fuel Measurement)

What it means (plain English)

The IAT sensor measures the temperature of the air entering the engine. This data helps the ECM adjust fuel delivery, timing, EGR, and turbo control.

A P0113 code means the ECM is seeing an abnormally high voltage signal from IAT Sensor 1. Since most IAT sensors are thermistors (resistance decreases as temperature increases), a high signal voltage usually means the ECM thinks the intake air is extremely cold (often −30°F or below).

Symptoms

  • Check Engine Light (MIL) illuminated
  • Hard starting in cold weather (ECM over-fuels thinking air is too cold)
  • Rough idle or hesitation when cold
  • Excess black smoke on startup
  • Reduced fuel economy
  • May affect turbo/EGR operation

Priority Level

Medium–High —
This won’t usually strand a truck immediately, but incorrect intake temperature data can cause poor drivability, hard starts, and higher emissions.

Common Causes

  • Unplugged or disconnected IAT sensor
  • Open circuit in IAT sensor wiring
  • Corroded or damaged connector pins
  • Failed IAT sensor (internal open circuit)
  • In rare cases, faulty ECM input

How Pros Diagnose It (step-by-step)

  1. Scan tool confirmation — verify P0113 and read IAT value. If it shows extremely low temps (e.g., −40°F), suspect open circuit.
  2. Visual inspection — check IAT sensor location (often integrated with MAF sensor on diesels).
  3. Wiring check — look for disconnected plugs, broken wires, or corrosion.
  4. Backprobe sensor — verify 5V reference and ground present.
  5. Resistance test — compare IAT sensor resistance to spec at current temperature.
  6. Substitute known-good sensor if wiring tests good.

Likely Fixes

  • Reconnect IAT sensor (if unplugged)
  • Replace faulty IAT sensor
  • Repair/replace damaged wiring or connector
  • Replace ECM (only if wiring and sensor test good, very rare)

Related/Companion Codes

  • P0112 — IAT Sensor 1 Circuit Low
  • P0101 — MAF Sensor Range/Performance
  • P0102/P0103 — MAF Low/High
  • P0401/P0402 — EGR Flow faults (can be influenced by incorrect air temp data)

Tech Notes (Quick Hits)

  • On Duramax engines, the IAT is often built into the MAF sensor — replacing the MAF usually fixes it.
  • On Cummins ISX/ISB, loose or corroded connectors are a common culprit.
  • On Powerstroke 6.4L/6.7L, aftermarket intakes can damage or misplace the IAT sensor.
  • Always check for an unplugged connector first — many P0113s are from accidental disconnection during filter service.

Severity: Medium–High — Repair Soon
A P0113 code means your truck’s intake air temperature sensor is reporting faulty high voltage, making the ECM think the incoming air is extremely cold. This throws off fueling and turbo control, often causing hard starts, smoke, or poor performance. Fixing the sensor or wiring quickly restores proper operation.

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