Symptoms of P0188
- Check-engine light on, sometimes with rough or uneven running.
- Hesitation, surging, or a noticeable change in fuel economy.
- Occasionally hard starting or a smell of unburnt fuel.
Common causes of P0188
- A failing or contaminated sensor (MAF, MAP, oxygen or air-fuel sensor).
- Intake or vacuum leaks, or an exhaust leak near an upstream sensor.
- Wiring, connector, or fuel-delivery problems that skew the reading.
Useful checks before replacing parts
- Check sensor B signal voltage, ground path, open circuits, short-to-voltage faults, connector fit, and sensor resistance.
- Inspect fuel-system wiring, unplugged connectors, corroded terminals, heat damage, and harness movement after service.
- Compare the high reading with sensor A, ambient, coolant, intake temperature, and actual fuel temperature after cold soak.
Related OBD-II codes
These nearby fuel / air entries can help compare wording and pin down the fault area.