Code B127 - PRND321 Sensor: Notes

The PRND321 sensor, part of the gear selector switch, is mounted on the transaxle and operates as a potentiometer that sends gear selection information to the BCM as a variable voltage signal. The PRND321 signal, circuit 356, is calculated as a percent of available ignition voltage to the gear selector position. Code B127 will set if the voltage signal is above or below the normal operating range, which could be the result of:

• Circuit 139, 356, or 736 open or shorted to ground.
• Faulty gear selector switch or switch adjustment.
• Faulty BCM.
• Faulty terminal contacts of the gear selector switch dash to engine harness interconnect or BCM.

1. Check BD41 to determine of PRND321 is within normal range of values.
2. A low BD41 value could be a misadjusted switch as well as an open or short to ground in circuit 139 or 356. Try adjusting switch before replacing.
3. Cycle the gear selector through all the gears, but disregard BD41 readings between gear selector positions. If a low reading is found at some particular position, try adjusting switch before replacing.
4. A high BD41 value indicates an open in the switch or circuit 736.

Fig 1: Code B127 - Schematic

Fig 2: Code B127 - PRND321 Sensor

Code B127 will also set if the Park/Neutral switch signal is faulty to the ECM. The ECM monitors the status of the switch position which closes when the gear selector is in the Park or Neutral position.

1. ECM input E174 displays the voltage state of circuit 434 at the ECM.
2. Disconnecting the switch connector and jumpering terminal 'A' to ground will determine if the switch is at fault or the ECM or an open in the related circuitry.
3. Disconnecting the switch will determine if the fault is due to switch, the ECM or a short to ground in circuit 434.