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P codepowertrainMedium severity

P2432Secondary Air Injection System Air Flow/Pressure Sensor Circuit Low (Bank 1)

The bank 1 secondary air injection pressure sensor signal is stuck below its normal range, indicating a short to ground or a failed sensor.

Definition

The PCM monitors a pressure sensor plumbed between the secondary air pump and the air switching valve to confirm the system delivers air to the exhaust during cold-start catalyst warm-up. This code sets when the bank 1 sensor's signal voltage stays below the plausible range — even a system at rest should read roughly atmospheric pressure, so a near-zero signal is electrically impossible. The MIL illuminates, the SAI readiness monitor will not run, and some applications (notably Toyota/Lexus V8 trucks) impose a reduced-power limp mode. Moisture that migrates back from the exhaust is a common underlying cause of sensor failure.

Common causes

  • Failed SAI pressure sensor reading low
  • Signal wire shorted to ground in the harness
  • Corroded or water-contaminated sensor connector
  • Open 5-volt reference feed to the sensor
  • Moisture intrusion from a leaking air switching valve damaging the sensor
  • PCM input fault (least common)

Common misdiagnoses

  • Secondary air pump replaced for a sensor-circuit fault
  • Air switching valves replaced without testing the sensor circuit first
  • Oxygen sensors or catalytic converter blamed for the code
  • PCM replaced before wiring is checked

Troubleshooting steps

  1. 1.Read the sensor PID at key-on, engine off

    The sensor should report approximately atmospheric pressure with the system at rest; a value pegged at or near zero confirms the circuit-low condition.

  2. 2.Check the 5-volt reference and ground at the sensor

    Back-probe the connector for a solid 5-volt supply and good ground; a missing reference produces a low signal and points upstream of the sensor.

  3. 3.Test the signal wire for a short to ground

    With the sensor and PCM disconnected, verify no continuity between the signal wire and chassis ground.

  4. 4.Inspect the connector and sensor for moisture

    Water or rusty residue in the connector or sensor port indicates exhaust moisture backflow, which also condemns the switching valve that allowed it.

  5. 5.Substitute the sensor and verify system operation

    With wiring proven good, replace the sensor, then command the air pump on with a scan tool and confirm a normal pressure rise and no code reset.

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