Code B127, Gear Selector Switch Circuit: Notes

Gear selector switch (or PRNDD21) is mounted on transaxle assembly. It is a multi-signal switch sending information relative to gear selector position to BCM and PCM. PRNDD21 switch assembly also contains neutral safety switch. PRNDD21 switch uses 4 discrete circuits to pull 4 BCM voltages low in various combinations to indicate each gear range. Voltage level of each circuit is represented in BD41 display as "0" equals grounded and "1" equals not grounded. Digits displayed represent decoder "A", "B", "C" and parity inputs in sequence.

Switch status can be seen by monitoring BD41 or ED31 data parameter, where switch status is displayed as a 4-digit binary number. Code B127 will set if following conditions exist:

• Ignition switch in ON position.
• Code B334 is not set (PCM UART data line is okay).
• BD41 does not agree with ED31.