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P codepowertrainLow severity

P0319Rough Road Sensor B

The rough-road sensor "B" signal is faulty, missing, or implausible, degrading the misfire monitor's ability to ignore rough pavement.

Definition

On vehicles with a second rough-road input — a "B" accelerometer channel or an additional wheel-speed-derived signal — the PCM cross-checks it against sensor "A" to decide when to suspend misfire detection over broken pavement. P0319 sets when the "B" signal is open, shorted, stuck, or disagrees with the primary input. There is no direct driveability effect, but the MIL turns on, false misfire codes can appear on rough surfaces, and the stored code will fail an OBD emissions inspection.

Common causes

  • Failed rough-road sensor "B" element
  • Open, shorted, or chafed signal wiring or a corroded connector
  • Missing wheel-speed data from the ABS module on designs that source the "B" signal from the network
  • Poor sensor ground or reference-voltage supply fault
  • PCM input circuit fault (rare)

Common misdiagnoses

  • Ignition components replaced for false misfire codes triggered on rough roads
  • Rough-road sensor "A" replaced when the "B" circuit is at fault
  • ABS wheel speed sensors replaced on vehicles with a dedicated accelerometer
  • PCM replaced before circuit testing

Troubleshooting steps

  1. 1.Scan for related codes first

    P0317/P0318 or ABS/U-codes set together point to a shared harness, supply, or network fault rather than the "B" sensor alone.

  2. 2.Compare both rough-road signals in live data

    Drive over a rough surface or rock the vehicle and confirm channels A and B track together; a flatlined or pegged B channel isolates the fault.

  3. 3.Test the sensor circuit at the connector

    Verify the reference voltage and ground, then confirm the signal responds when the sensor body is lightly tapped or bounced.

  4. 4.Inspect and wiggle the harness

    Watch live data while flexing the loom near the sensor and floor grommets to expose intermittent opens common in body-mounted runs.

  5. 5.Replace the sensor if the wiring is proven

    With good supply and ground and no signal response, install a new sensor and verify the code does not reset over a rough-road test drive.

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