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Park/Neutral Relay Input (Q45) Test

  1. Backprobe ECU terminal No. 44 with positive lead of a 10-megohm DVOM. Connect negative lead to a good ground. See appropriate WIRING DIAGRAMS article to identify ECU terminals.
  2. With gear selector in any position except Park or Neutral, voltmeter should read 8-10 volts. With gear selector lever in Park or Neutral, voltmeter should read approximately zero volt.
  3. If voltmeter reads zero volt at all times, check for short circuit between transmission control unit terminal No. 13 and ECU. If wire is okay, check for inhibitor switch misadjustment or short to voltage between A/T inhibitor switch and transmission control unit.
  4. If wiring and switch are okay, substitute known good transmission control unit. If circuit still does not operate correctly, substitute known good ECU.
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