P1148 – HO2S21 Heater Circuit Fault (Ford)

Description

P1148 Ford indicates a malfunction in the heater circuit of the downstream O2 sensor on Bank 2.

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Symptoms

  • Delayed closed-loop
  • Poor fuel economy
  • Rough idle

Causes

  • Failed heater element
  • Wiring issues
  • Blown fuse

Diagnosis

  • Check heater resistance
  • Inspect wiring
  • Measure heater voltage

Repair

  • Replace O2 sensor
  • Repair wiring