Visual Inspection of HO2S
1. Visually/physically inspect following items:
  - Inspect the front HO2S for Contaminated, deteriorated or aged Front HO2S
  - If contamination is evident on the HO2S, replace contaminated sensor
2. Is the HO2S visually/physically OK?
  YES
  - Go to step 2.
  NO
  - Substitute with a known-good HO2S and check for proper operation. If the problem is corrected, replace HO2S and go to "VERIFICATION OF VEHICLE REPAIR "
Check performance of HO2S
1. Connect scan tool. Turn Engine "ON"
2. Warm-up the engine to normal engine temperature.
3. Monitor signal waveform of HO2S with scan tool.
  Specification: Voltage will vary from 0.1 to 0.9 V
  
  Fig 1: Signal Waveform Graph
  Courtesy of KIA MOTORS AMERICA, INC.
4. Is the sensor signal switching properly?
  YES
  - Substitute with a known-good PCM and check for proper operation. If the problem is corrected, replace PCM and go to "VERIFICATION OF VEHICLE REPAIR " procedure.
  NO
  - Substitute with a known-good HO2S and check for proper operation. If the problem is corrected, replace HO2S and go to "VERIFICATION OF VEHICLE REPAIR " procedure.

NOTE: There is a memory reset function on scan tool that can erase optional parts automatically detected and memorized by PCM. Before or after testing PCM on the vehicle, use this function to reuse the PCM on the others

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Component Inspection

Use the Manual With the Right Hardware

When to See a Mechanic