O2 Signal fluctuates between 1V and 50V after switching to Narrowband
Posted: Thu Apr 23, 2026 9:08 am
"Hello,
I am using a Hondata KPro V4. A year ago, my car was professionally tuned using a PLX wideband sensor. Now, I need to pass the German 'TÜV' inspection (equivalent to MOT in the UK or Safety/Emissions in the US). For their diagnostic software to pass the car, they need to see a fluctuating voltage signal from a narrowband/stock O2 sensor.
My goal was to temporarily switch back to a narrowband (stock) sensor for the inspection. However, I am facing the following issue:
The Problem: In the KManager software, the 'O2' reading shows a fluctuates between 1V and 50V and the Lambda value is frozen at 0.69.
Physical Measurement: I have measured the signal at the ECU pin input, and it correctly fluctuates between 0.1V and 0.9V.
Software Settings: I have updated the settings in KManager to 'Narrowband' under the 'Closed Loop' tab.
Despite these changes, the software does not seem to process the actual voltage arriving at the pin. Since the calibration was originally created by a tuner, I am wondering if there is a fundamental setting or a specific lock/modification in the software that prevents the ECU from switching back to the narrowband input.
I have basic knowledge of the software but am stuck at this point. Any advice on what to check in the calibration settings would be greatly appreciated."
I am using a Hondata KPro V4. A year ago, my car was professionally tuned using a PLX wideband sensor. Now, I need to pass the German 'TÜV' inspection (equivalent to MOT in the UK or Safety/Emissions in the US). For their diagnostic software to pass the car, they need to see a fluctuating voltage signal from a narrowband/stock O2 sensor.
My goal was to temporarily switch back to a narrowband (stock) sensor for the inspection. However, I am facing the following issue:
The Problem: In the KManager software, the 'O2' reading shows a fluctuates between 1V and 50V and the Lambda value is frozen at 0.69.
Physical Measurement: I have measured the signal at the ECU pin input, and it correctly fluctuates between 0.1V and 0.9V.
Software Settings: I have updated the settings in KManager to 'Narrowband' under the 'Closed Loop' tab.
Despite these changes, the software does not seem to process the actual voltage arriving at the pin. Since the calibration was originally created by a tuner, I am wondering if there is a fundamental setting or a specific lock/modification in the software that prevents the ECU from switching back to the narrowband input.
I have basic knowledge of the software but am stuck at this point. Any advice on what to check in the calibration settings would be greatly appreciated."