P0112 medium Severity

P0112: Intake Air Temperature Sensor 1 Circuit Low Input

The engine control module (ECM) may receive incorrect intake air temperature data leading to suboptimal fuel‑air mixture and ignition timing; this can cause rough idle, decreased performance, and reduced fuel economy.

Overview

P0112 indicates a low voltage input from the intake air temperature (IAT) sensor circuit, often due to sensor faults, wiring issues, or faulty connections affecting engine performance and emissions.

Common Symptoms

  • Check Engine Light (MIL) illuminated
  • Reduced engine performance or rough idle
  • Poor fuel economy or hesitation
  • Hard starting or stalling

Most Common Causes

Faulty intake air temperature (IAT) sensor high

The sensor may internally short or fail, leading to a low voltage signal to the ECM.

Damaged or corroded wiring or connectors in the IAT circuit high

Open circuits, short to ground, or poor connections frequently lead to low input voltages.

Short to ground on signal circuit medium

Electrical shorting can pull reading low even if sensor is functional.

Faulty engine control module (ECM) low

Rare but possible, especially after verifying sensor and wiring integrity.

Diagnostic Steps

  1. Connect an OBD‑II scanner and confirm P0112 is present; view live IAT sensor data.
    Expected: IAT voltage reading persistently low (below expected range).
    Interpretation: Confirms code validity and low input condition.
  2. Visually inspect IAT sensor harness, connectors, and wiring for damage or corrosion.
    Expected: Intact connectors with no corrosion, broken wires, or loose terminals.
    Interpretation: Any visible defects indicate potential wiring/circuit repair.
  3. Measure voltage at IAT sensor reference, signal, and ground using a multimeter.
    Expected: Approximately 5 V reference, good ground, and variable signal based on temperature.
    Interpretation: Out‑of‑range or constant low voltage suggests circuit fault or sensor failure.
  4. Remove the IAT sensor and check resistance with multimeter according to temperature specifications.
    Expected: Resistance changes proportionally with temperature; matches manufacturer's spec.
    Interpretation: If resistance does not change appropriately, the sensor is defective.
  5. If wiring and sensor check good, consider ECM input testing or professional diagnostics.
    Expected: ECM correctly reads other sensors but still shows low IAT input.
    Interpretation: Supports possible ECM fault with low confidence.

Repair Solutions

Replace faulty intake air temperature (IAT) sensor easy
Estimated Cost: $50 - $200

Common and direct fix when sensor tests out of spec.

Repair or replace damaged wiring/connectors in the IAT circuit medium
Estimated Cost: $50 - $300

Costs vary by extent of wiring damage and labor.

Professional ECM diagnostics or module replacement hard
Estimated Cost: $300 - $1200

Required only after thorough sensor/circuit validation.

Common Misdiagnoses

Avoid these common diagnostic mistakes:

  • Replacing the IAT sensor without inspecting wiring/circuits
  • Assuming air filter alone causes the code without further analysis
  • Misattributing poor performance to MAF sensor without confirming IAT circuit integrity

Frequently Asked Questions

What is the definition of the P0112 engine code?

Intake Air Temperature Sensor 1 Circuit Low Input is the standard definition for P0112. This diagnostic code is triggered when the ECU detects a problem in the Air Intake.

Reflecting on severity: How bad is P0112?

With a severity level of medium, the engine control module (ECM) may receive incorrect intake air temperature data leading to suboptimal fuel‑air mixture and ignition timing; this can cause rough idle, decreased performance, and reduced fuel economy.

What happens when the P0112 code is active?

Common symptoms include: Check Engine Light (MIL) illuminated, Reduced engine performance or rough idle, Poor fuel economy or hesitation. You might also notice the Check Engine Light is on.

Common triggers for the P0112 error

The most common causes are: Faulty intake air temperature (IAT) sensor, Damaged or corroded wiring or connectors in the IAT circuit, Short to ground on signal circuit.

Repair cost breakdown for P0112

Expect to pay around $200 if the issue is a Replace faulty intake air temperature (IAT) sensor, but up to $1200 if the Professional ECM diagnostics or module replacement needs replacement.

Is P0112 a generic or manufacturer-specific code?

P0112 is not specific to any one brand. It can appear on Ford, Dodge, Toyota, Honda, Jeep, and other vehicles.

User Comments (0)

Share your experience or ask a question about this code.

Be the first to share your experience with P0112!