What can cause upstream O2 sensor to drop voltage to 0v for 4-5 seconds after the throttle is left go, after which it switches back to normal fluctuation (0.1-0.85v)? There is a noticeable 'hiccup' after gas pedal is left go (every time).
What can cause this issue? Is there any correlation to the engine temperature thermostat (engine being too cold)?
For the reference:
- Vehicle: Hyundai Coupe '07 2.0
- Closed loop operation (Long-term fuel trim: around -1% to 1% at most times).
- Issue: persistent p0133 even after three sensors were changed (NTK, Denso, Bosch - searched by OEM part number reference).
