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P codepowertrainMedium severity

P2746Intermediate Shaft Speed Sensor "B" Circuit Range/Performance

The transmission's intermediate shaft speed sensor "B" is producing a signal that doesn't agree with the other transmission speed sensors.

Definition

Transmissions with multiple internal shafts (many CVTs, dual-clutch units, and 6+ speed automatics) use intermediate shaft speed sensors so the TCM can verify gear ratios and clutch slip. P2746 sets when sensor "B" reports a speed that is erratic or implausible compared with the input and output shaft speeds run through the current gear ratio. Symptoms include harsh or erratic shifting, ratio-error behavior, and the transmission dropping into limp mode with the MIL illuminated; the fault undermines the TCM's ability to detect real slip, so it should not be ignored.

Common causes

  • Failing intermediate shaft speed sensor B (weak or noisy output)
  • Metal debris collected on the sensor's magnetic tip
  • Intermittent wiring or connector fault in the sensor circuit
  • Damaged tone ring/reluctor or excessive air gap
  • Missing or low sensor supply voltage (Hall-effect types)
  • Internal transmission damage causing actual erratic shaft speed

Common misdiagnoses

  • Valve body replaced for a speed sensor fault
  • Transmission replaced when only a sensor or wiring was bad
  • Wrong speed sensor replaced (input or output instead of intermediate B)
  • Fluid service alone expected to fix an electrical/sensor fault

Troubleshooting steps

  1. 1.Compare all speed sensor PIDs on a road test

    Graph input, output, and intermediate shaft speeds; with the gear ratio applied they should track proportionally, and a signal that spikes or drops out identifies the bad channel.

  2. 2.Inspect the sensor tip

    Remove the sensor and check for metallic debris stuck to the magnet, which distorts the signal and also hints at internal wear.

  3. 3.Check wiring and connector

    Inspect the sensor connector for fluid intrusion and corrosion, and wiggle-test the harness while watching the sensor PID.

  4. 4.Verify sensor power and signal

    For Hall-effect sensors confirm supply voltage and ground, then scope the signal for clean square waves; for VR sensors measure coil resistance against spec.

  5. 5.Inspect the tone ring if accessible

    Look for damaged or missing teeth and correct sensor seating depth/air gap before condemning the sensor a second time.

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