FixItFor.Us
P codepowertrainMedium severity

P0437Catalyst Temperature Sensor Low Input (Bank 2)

The Bank 2 catalyst temperature sensor signal voltage has fallen below its normal operating range.

Definition

P0437 sets when the PCM sees the Bank 2 catalyst temperature sensor signal below the minimum plausible voltage threshold, which almost always indicates a short to ground or an internally shorted sensor rather than a real temperature condition. The PCM discards the reading and suspends catalyst temperature monitoring on that bank. The engine runs normally with the MIL on, and the vehicle will fail an emissions inspection until the circuit is repaired.

Common causes

  • Signal wire chafed to ground along the exhaust or frame rail
  • Internally shorted sensor element
  • Moisture or corrosion bridging connector terminals
  • Harness pinched during previous exhaust or driveline service
  • ECM input fault (rare)

Common misdiagnoses

  • Bank 2 converter replaced for an electrical circuit-low code
  • Sensor replaced when the harness short to ground remains
  • ECM replaced before wiring checks are completed

Troubleshooting steps

  1. 1.Confirm the pegged PID

    A Bank 2 catalyst temperature reading frozen at one extreme while Bank 1 tracks normally confirms an electrical fault, not a real exhaust condition.

  2. 2.Unplug the sensor and observe the change

    If the PID snaps to the open-circuit default with the sensor disconnected, the short is inside the sensor; no change points to the harness or ECM.

  3. 3.Test for a short to ground

    With both ends of the circuit disconnected, resistance from the signal wire to chassis ground should read OL; anything low confirms a chafe-through.

  4. 4.Trace the harness routing

    Follow the Bank 2 sensor lead across the exhaust and crossmember, checking every contact point and heat shield edge for worn insulation.

  5. 5.Measure the sensor element

    Compare its resistance at a known temperature to spec and to the Bank 1 sensor; a near-zero reading condemns the sensor.

Related codes