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P codepowertrainMedium severity

P043DCatalyst Temperature Sensor Circuit High (Bank 2 Sensor 2)

The downstream catalyst temperature sensor on Bank 2 is reading above its normal voltage range, usually because the circuit is open or shorted to voltage.

Definition

The PCM monitors the Bank 2 Sensor 2 catalyst temperature signal — the mid-bed or outlet sensor on the bank opposite cylinder 1 — and sets P043D when that signal exceeds its maximum plausible threshold. Because the ECM's pull-up voltage drives an open circuit high, an open sensor element or broken wire is the most common trigger. The MIL illuminates with no driveability change; on diesel applications the PCM may block active DPF regeneration until the circuit is repaired, allowing soot to accumulate over time.

Common causes

  • Open sensor element from thermal cycling (common at high mileage)
  • Broken signal or return wire near the exhaust heat zone
  • Unplugged, corroded, or backed-out connector terminal
  • Signal wire shorted to voltage from harness chafe
  • ECM input circuit fault (rare)

Common misdiagnoses

  • DPF or Bank 2 converter replaced for a sensor circuit fault
  • Wrong exhaust temperature sensor replaced due to position confusion
  • Sensor replaced twice while a broken harness wire goes unfound

Troubleshooting steps

  1. 1.Identify Bank 2 Sensor 2 precisely

    Use service information to pinpoint this sensor among the several exhaust temperature sensors — replacing the wrong position is the most common wasted repair.

  2. 2.Compare all temperature PIDs

    On a warm engine, the suspect PID pegged at default or maximum while its neighbors read normally confirms an electrical open.

  3. 3.Jumper the harness terminals

    With the sensor unplugged, bridge the harness side and watch the PID; a swing to the opposite extreme proves wiring and ECM good and condemns the sensor.

  4. 4.Check continuity to the ECM

    Measure both circuit wires end to end; resistance above a few ohms means a break, bad crimp, or corroded terminal.

  5. 5.Measure sensor resistance

    Compare the element at a known temperature to the specification chart; an open (OL) reading at room temperature confirms element failure.

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