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Code I027 - PRND321 Sensor Failure

  1. Park/Neutral position switch is mounted on transaxle assembly. There are 2 parts to this diagnostic code definition. The first part results in electronic PRND321 illuminating all display segments around each of the gear selections. If ignition switch is in either UNLOCK or RUN position, Code I034 (Loss Of PCM Data) is not currently set, PRND321 state as decoded by IPC indicates Park or Neutral and PCM does not indicate Park or Neutral, or vise versa, and this remains true for .6 second, then PRND321 display illuminates all display segments around each of the gear selections. If this condition continues for 3 seconds or more, then Code I027 sets current.
  2. If PCM Code P091 is also set, see TESTS W/CODES - 4.6L - Concours or TESTS W/CODES - 4.9L - DeVille article in the ENGINE PERFORMANCE section. If PCM Code P091 is not set, go to next step.
  3. Turn ignition on. Shift transmission into Park. Using ID41 parameter, read PRND321 display. If ID41 display matches those in the GEAR SELECTOR POSITION  table for Park position, go to next step. If display does not match GEAR SELECTOR POSITION table, go to step 5).
    GEAR SELECTOR POSITION

    Gear Position ID41 Display A/B ID41 Display C/P
    Park (P) LO/HI HI/LO
    Reverse (R) LO/LO HI/HI
    Neutral (N) HI/LO HI/LO
    Drive (D) HI/LO LO/HI
    Drive 3 (3) LO/LO LO/LO
    Drive 2 (2) LO/HI LO/HI
    Drive 1 (1) HI/HI LO/LO
  4. Compare ID41 display in each gear selection position to the GEAR SELECTOR POSITION  table. If ID41 display matches table for all combinations, replace IPC. If ID41 display does not match table for all combinations, check wiring for an open or short circuit to ground.
  5. If ID41 does not display high for all inputs, go to next step. If ID41 displays high for all inputs, check Black/White wiring for an open circuit. Check all in-line connectors for good terminal contact. Check Park/Neutral position switch for correct operation. If all checks are okay, replace IPC.
  6. If ID41 does not display high or low for all inputs, move gear selector lever from Park to Drive. Repair wiring associated with input that does not change. Repeat system check.
  7. If ID41 displays high for all inputs, turn ignition off. Disconnect connector at Park/Neutral switch Black/White wire. Turn ignition on. If ID41 now displays high for all inputs, replace Park/Neutral switch. Repeat system check. If ID41 does not display high for all inputs, check all PRND321 circuits for a short to ground. If all circuits are okay, replace IPC.
NOTE: Following test should be used when multiple codes exist.
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