What are the common causes of the P0110 code on a Toyota?

cause_iat_sensor, cause_wiring_damage, cause_connector_corrosion

How much does it cost to fix the P0110 code?

The estimated repair cost for the P0110 code is $50 - $200. This includes parts and labor.

P0110Toyota YarisYears: 1996 - 2026

Intake Air Temperature (IAT) Circuit Malfunction

Reviewed by ASE Certified Technician

Is It Safe to Drive?Driving with a P0110 code is generally not immediately dangerous, but it warrants caution. The engine's computer relies on accurate IAT data to calculate optimal fuel delivery and ignition timing. An incorrect IAT reading can lead to an overly rich or lean fuel mixture, resulting in reduced fuel economy, increased emissions, rough idling, hesitation, or a lack of power. Prolonged driving with an improper air-fuel mixture can potentially lead to more severe issues, such as catalytic converter damage, spark plug fouling, or carbon buildup, which are expensive to repair. It is advisable to diagnose and repair this issue promptly to prevent further complications and maintain optimal engine performance.

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What does this mean?

The IAT sensor measures the temperature of the air entering the engine. Code P0110 indicates a general malfunction in the IAT sensor circuit.

Disclaimer: This diagnostic code is part of the standard OBD2 system and can apply to Toyota Yaris models manufactured from 1996 to 2026. However, please note that the presence of this specific code depends on your vehicle's exact engine configuration, options, and production year.

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Common Causes

Faulty Intake Air Temperature (IAT) sensor

Damaged, chafed, or broken wiring harness

Corroded or loose electrical connector

Symptoms to Watch For

Check Engine Light is illuminated
Difficulty starting the engine
Rough or unstable idle
Decreased fuel economy

How to Diagnose

**1. Thorough Visual Inspection and Connector Integrity Check:** Begin by locating the Intake Air Temperature (IAT) sensor. On many vehicles, the IAT sensor is a standalone unit mounted in the intake ducting, while on others, it's integrated into the Mass Air Flow (MAF) sensor. Visually inspect the sensor and its electrical connector for any obvious signs of damage, such as frayed wires, corrosion on the terminals, bent pins, or a loose connection. Ensure the connector is fully seated and locked. Trace the wiring harness from the IAT sensor back towards the Powertrain Control Module (PCM) as far as visible, looking for any chafing, cuts, or signs of rodent damage that could indicate an open or short circuit.

**2. IAT Sensor Resistance Test (Ohmmeter):** Disconnect the IAT sensor's electrical connector. Using a digital multimeter set to the ohms (Ω) scale, measure the resistance across the two terminals of the IAT sensor itself. Compare this reading to the specified resistance values for your vehicle's IAT sensor at ambient temperature, which can typically be found in a factory service manual or reliable repair database. As a general rule, a thermistor-type IAT sensor's resistance will decrease as the air temperature increases. If the sensor shows an open circuit (infinite resistance) or a short circuit (near zero resistance), or if the reading is significantly out of specification for the current ambient temperature, the sensor is faulty.

**3. IAT Circuit Voltage and Ground Reference Test:** With the IAT sensor disconnected and the ignition key in the 'ON' position (engine OFF), use a multimeter to test the voltage at the IAT sensor's electrical connector. Consult a wiring diagram for your specific vehicle to identify the 5-volt reference wire and the ground wire. Measure the voltage between the 5-volt reference wire and a known good chassis ground; you should observe approximately 5.0 volts. Next, measure the voltage between the ground wire at the connector and a known good chassis ground; this reading should be very close to 0 volts. Finally, check for continuity between the ground wire at the connector and chassis ground (resistance should be very low, typically less than 0.5 ohms). Absence of 5V indicates an open in the reference circuit or a PCM issue, while a missing ground indicates an open in the ground circuit.

**4. Signal Wire Continuity and Short-to-Ground/Power Test:** With both the IAT sensor connector and the PCM connector disconnected, perform continuity tests on the signal wire. Measure the resistance between the IAT signal terminal at the sensor connector and its corresponding terminal at the PCM connector. Resistance should be very low (ideally less than 0.5 ohms). Next, check for shorts to ground by measuring resistance between the signal wire terminal at either connector and a known good chassis ground; resistance should be infinite. Also, check for shorts to power by measuring resistance between the signal wire and any 12V power source (e.g., battery positive or a fused ignition wire); resistance should also be infinite. Any low resistance readings indicate a short circuit in the wiring.

**5. Live Data Monitoring with Scan Tool:** If all previous circuit and sensor tests pass, connect an OBD2 scan tool capable of displaying live data. Monitor the IAT sensor reading with the engine cold and off. The displayed temperature should closely match the ambient air temperature and the engine coolant temperature (if the engine is cold). Start the engine and observe the IAT reading as the engine warms up and air flows through the intake. The temperature should respond plausibly. If the reading is stuck at an extremely high or low value, erratic, or unresponsive despite passing static tests, it could indicate an intermittent sensor failure, an intermittent wiring issue, or a PCM internal fault.

Common Solutions

**Replace the Intake Air Temperature (IAT) Sensor:** This is the most frequent solution if the sensor itself fails the resistance test, provides implausible data, or is physically damaged. Ensure the replacement sensor is an OEM equivalent or high-quality aftermarket part specific to your vehicle.

**Repair or Replace Damaged Wiring or Connector:** If diagnostic steps reveal an open circuit, short circuit, or excessive resistance in the IAT sensor's wiring harness or a corroded/damaged connector, the affected section must be repaired or replaced. Use proper wiring repair techniques (e.g., soldering and heat-shrink tubing) to ensure a durable connection.

**Clean the Mass Air Flow (MAF) Sensor (if IAT is integrated):** If your vehicle's IAT sensor is integrated into the MAF sensor, sometimes a dirty MAF sensor can cause inaccurate IAT readings. Carefully clean the MAF sensor element, including the IAT thermistor, with a specialized MAF sensor cleaner. Do not use other solvents or brushes.

**Replace the Powertrain Control Module (PCM):** In very rare instances, if all sensor and wiring tests confirm integrity and functionality, but the P0110 code persists with incorrect IAT readings, the PCM itself may be faulty. This is a last resort and should only be considered after exhaustive testing has ruled out all other possibilities, as PCM replacement is costly and often requires programming.

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Repair Estimate

$50 - $200

Parts$20 - $300

Labor$60 - $250

DIY Difficulty

Easy

Other Popular Toyota Codes

P0119 P0124 P0100

Intake Air Temperature (IAT) Circuit Malfunction

Reviewed by ASE Certified Technician

What does this mean?

The IAT sensor measures the temperature of the air entering the engine. Code P0110 indicates a general malfunction in the IAT sensor circuit.

How to Diagnose

Common Solutions

What does this mean?

Common Causes

Symptoms to Watch For

How to Diagnose

Common Solutions

Join the Discussion

Repair Estimate

DIY Difficulty

Other Popular Toyota Codes

Scanning Engine...

What does this mean?

Common Causes

Symptoms to Watch For

How to Diagnose

Common Solutions

Join the Discussion

Repair Estimate

DIY Difficulty

Other Popular Toyota Codes