OBD-II Trouble Code P0098: Intake Air Temperature Sensor 2 Circuit High Explained

The P0098 diagnostic trouble code is a common issue in modern vehicles equipped with OBD-II systems, including EOBD compliant cars in Europe. This code, specifically “Intake Air Temperature Sensor 2 Circuit High,” signals a potential problem within your car’s air intake system and its sensor readings. While it’s a generic powertrain code applicable across many makes and models, understanding the specifics of P0098 is crucial for accurate diagnosis and repair.

Understanding the P0098 Code: IAT Sensor 2 Circuit High

Your vehicle’s Powertrain Control Module (PCM) relies on accurate data from various sensors to optimize engine performance and efficiency. One critical sensor is the Intake Air Temperature (IAT) sensor. The P0098 code indicates that the PCM has detected an abnormally high voltage signal from the IAT Sensor 2 circuit.

To elaborate, the PCM sends a 5-volt reference voltage to the IAT sensor 2. This sensor is a thermistor, meaning its resistance changes with temperature variations. As the intake air temperature rises, the sensor’s resistance decreases, and vice versa. Lower temperatures result in a higher signal voltage being sent back to the PCM. A P0098 code is triggered when the PCM registers a signal voltage exceeding the expected high threshold – typically above 5 volts – from the IAT Sensor 2. This suggests a potential fault in the sensor circuit, not necessarily indicating excessively hot intake air, but rather an electrical issue.

Symptoms Associated with P0098

In many cases, the most noticeable symptom of a P0098 code is the illumination of the Malfunction Indicator Lamp (MIL), commonly known as the Check Engine Light or Service Engine Soon light on your dashboard. You might not experience any other immediately apparent drivability issues. However, it’s crucial to address this code promptly as inaccurate IAT readings can potentially affect engine performance and fuel economy over time if left unaddressed.

Common Causes of a P0098 Code

Several factors can lead to a P0098 code. Pinpointing the exact cause is the first step in effective repair. Here are some potential culprits:

• Faulty IAT Sensor 2: The sensor itself might have internally failed and is sending incorrect readings.
• Connection Issues at the IAT Sensor 2: A loose, corroded, or damaged connector at the IAT sensor can disrupt the electrical signal, leading to a high voltage reading.
• Open Circuit in IAT Ground or Signal Wire: A break or open in the wiring of the IAT sensor’s ground or signal circuits can cause an incorrect voltage signal.
• Short to Voltage in IAT Signal or Reference Circuit: If the IAT sensor’s signal or reference circuit is shorted to a voltage source, it can artificially inflate the voltage reading detected by the PCM.
• Wiring Interference: If the IAT sensor wiring harness is routed too closely to high-voltage components like the alternator or spark plug cables, electromagnetic interference can induce voltage spikes in the sensor circuit.
• PCM Malfunction (Less Likely): While less common, a faulty PCM could misinterpret sensor signals or incorrectly set the P0098 code. This is usually considered after ruling out other possibilities.

Diagnosing and Resolving P0098

Troubleshooting a P0098 code requires a systematic approach. Here’s a step-by-step guide to help you diagnose and potentially resolve the issue:

1. Initial Scan Tool Check: Use an OBD-II scan tool to confirm the presence of the P0098 code and check for any other related codes. Crucially, check the live IAT sensor reading on the scan tool.

   • Logical Reading: If the IAT reading appears reasonable and within expected temperature ranges, the fault might be intermittent.
   • Illogical Low Reading (e.g., below -30 degrees Fahrenheit): This suggests a circuit issue. Proceed to the next step.
   • No Reading: Indicates a potential open circuit or sensor malfunction.

2. Jumper Wire Test (Simulating High Temperature):

   • Disconnect the IAT Sensor 2 connector.
   • Use a jumper wire to bridge the signal and ground pins within the harness connector (the PCM side, not the sensor side).
   • Observe the IAT reading on the scan tool. It should now display a very high temperature reading (e.g., 280°F or higher).
     • High Reading Achieved: This indicates the wiring is likely intact, and the problem might be the sensor itself or a poor connection at the sensor.
     • No High Reading: This suggests a problem in the wiring harness between the connector and the PCM.

3. Ground Circuit Test: If the jumper wire test doesn’t yield a high temperature reading, test the ground circuit.

   • With the jumper wire still in place between the signal circuit and chassis ground (bare metal part of the car’s frame), check the IAT reading on the scan tool again.
     • High Reading Now: This points to an open circuit specifically in the IAT ground wire. Inspect the ground wire for breaks or poor connections.

4. 5-Volt Reference Voltage Check: If you are still not getting a reading on the scan tool, the 5-volt reference voltage from the PCM might be missing.

   • Use a Digital Volt-Ohm Meter (DVOM) to check for the 5-volt reference at the IAT sensor connector (with the sensor disconnected and ignition ON).
     • No 5-Volt Reference: Indicates a potential PCM issue or a break in the 5-volt reference wire.
     • 5-Volt Reference Present: Proceed to check the signal wire continuity.

5. Signal Wire Continuity Test:

   • Disconnect the PCM connector and the IAT sensor connector.
   • Use the DVOM in continuity mode to check for continuity in the IAT signal wire between the PCM connector pin and the IAT sensor connector pin.
     • No Continuity: Indicates an open circuit in the signal wire. Repair or replace the wire.

Related OBD-II Trouble Codes

Several other OBD-II codes relate to the Intake Air Temperature sensor and its circuit. These include:

• P0095, P0096, P0097, P0099, P0110, P0111, P0112, P0113, P0114, P0127

Understanding these related codes can provide a broader context when diagnosing issues within the air intake system.

Need Further Assistance with P0098?

If you require more specific guidance or have further questions regarding the P0098 trouble code, we encourage you to post your question in our FREE car repair forums. Our community of experienced technicians and automotive enthusiasts is ready to assist you.

Disclaimer: This information is for informational purposes only and should not be considered professional repair advice. We are not liable for any actions taken based on this information. Always consult with a qualified technician for vehicle repairs.