P0098 - Intake Air Temperature Sensor (IAT) Sensor '2' Circuit High (Bank 1)
System
Powertrain (Engine & Gearbox)
Technical Description
The control module has detected a fault in the Intake Air Temperature Sensor (IAT) Sensor '2' Circuit High (Bank 1) (P0098). The signal is above the upper threshold, typically from an open circuit, poor connection, or a short to battery voltage. Pertains to downstream oxygen sensor (post-catalyst diagnostic sensor) evaluating catalytic converter conversion efficiency.
Multimeter Test Points & Nominal Values
| Test Point / Component | Measurement | Nominal Target Range | Test Condition |
|---|---|---|---|
| Intake Air Temperature Sensor (IAT) Sensor '2' Circuit High (Bank 1) – Resistance at 20 °C | Resistance (kΩ) | 2.0 - 3.0 kΩ | Sensor disconnected, cold engine |
| Intake Air Temperature Sensor (IAT) Sensor '2' Circuit High (Bank 1) – Resistance at 80 °C | Resistance (Ω) | 250 - 400 Ω | Sensor disconnected, at operating temp |
| Intake Air Temperature Sensor (IAT) Sensor '2' Circuit High (Bank 1) – Signal Voltage | Voltage (V) | 0.3 - 4.5 V (falls as temperature rises) | Ignition ON, sensor connected |
| 5 V Reference / Signal Ground | Voltage (V) | 4.95 - 5.05 V / < 0.05 V | At sensor connector |
Sensor disconnected, cold engine
Sensor disconnected, at operating temp
Ignition ON, sensor connected
At sensor connector
Oscilloscope Waveform Analysis
30 s/div, 1 V/divPossible Causes
Open circuit on signal wire, spread terminal pin, or short to power feed at Intake Air Temperature Sensor (IAT) Sensor '2' Circuit High (Bank 1)
Bank 1 specific:Inspect wiring harness to cylinder bank 1 (firewall/right bank, exposed to exhaust manifold heat).
Sensor 2 (Downstream post-cat):Inspect underbody wiring for mechanical road-debris damage or water intrusion inside the subframe connector.
Chafed or pinched wiring harness along the signal path to Intake Air Temperature Sensor (IAT) Sensor '2' Circuit High (Bank 1)
Poor ground connection or excessive voltage drop (> 0.1 V) at the ground point for Intake Air Temperature Sensor (IAT) Sensor '2' Circuit High (Bank 1)
Defective internal output driver or reference circuit in the control module for Intake Air Temperature Sensor (IAT) Sensor '2' Circuit High (Bank 1)
Symptoms
Recommended Solution
Monitor downstream sensor voltage at steady cruise (should hold steady between 0.55 and 0.75 V; active switching flags depleted catalyst).
Cross-swap the component on Bank 1 with Bank 2 to rule out mechanical oil passages and internal timing wear.
Measure signal terminal voltage with ignition ON and sensor unplugged to determine if ECM pull-up is active or harness is shorted to 12V.
Verify loaded supply voltage and harness terminal pins at Intake Air Temperature Sensor (IAT) Sensor '2' Circuit High (Bank 1).
Check circuit continuity and ground-side voltage drop (< 0.05 V) for Intake Air Temperature Sensor (IAT) Sensor '2' Circuit High (Bank 1).
Replace the sensor if resistance is off-curve, otherwise repair wiring/connector.
Mechanic's Tip
Jumper the sensor connector and watch the scan tool: the value must peg to max temp instantly. Short it to ground and it must peg to min. If the value sweeps freely the sensor is at fault — otherwise the wiring or module is.