FixItFor.Us
P codepowertrainMedium severity

P2749Intermediate Shaft Speed Sensor "C" Circuit

A general electrical fault has been detected in the circuit for the transmission's intermediate shaft speed sensor "C".

Definition

On transmissions that use three or more internal shaft speed sensors, the TCM monitors each sensor circuit for opens, shorts, and implausible electrical values. P2749 is the general circuit code for intermediate shaft speed sensor C and sets when the circuit's voltage or signal falls outside acceptable limits. Loss of a shaft speed input degrades ratio and slip monitoring, so expect erratic or harsh shifting, possible limp mode operation, and an illuminated MIL.

Common causes

  • Failed intermediate shaft speed sensor C
  • Open or shorted wiring in the sensor circuit
  • Corroded or fluid-contaminated connector terminals
  • Chafed internal transmission harness
  • Damaged tone ring or incorrect sensor air gap
  • Failed TCM input circuit (rare)

Common misdiagnoses

  • Valve body replaced for a sensor circuit fault
  • Transmission replaced when wiring was at fault
  • Sensors A or B replaced instead of sensor C
  • TCM replaced without basic circuit testing

Troubleshooting steps

  1. 1.Identify sensor C's location and circuit

    Use service information to positively identify which physical sensor is "C" on this transmission, as multiple identical sensors are usually clustered together.

  2. 2.Check live data while driving

    Graph sensor C against the input and output shaft speeds; dropouts, spikes, or a flatline localize the fault to that channel.

  3. 3.Inspect the connector and harness

    Look for transmission fluid inside the connector, corroded terminals, and harness chafe points, then wiggle-test while watching the PID.

  4. 4.Test the sensor electrically

    Verify supply voltage and ground at the connector for Hall-effect designs, or measure coil resistance against spec for VR designs, then scope the output signal.

  5. 5.Replace the sensor and verify

    If wiring and power check good, replace sensor C, clear the code, and confirm a stable proportional signal through all gears on a road test.

Related codes