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DTC P1899: P/N Switch Performance (A/T): Testing

  1. Turn ignition on. Using scan tool, read DTCs. If GOOD TRIP counter is displayed for P1899 and displayed count is "0", go to next step. If GOOD TRIP counter is not displayed for DTC P1899 or displayed count is not "0", go to step  7 .
  2. Apply parking brake. Using scan tool, monitor PNP switch input state while moving shift lever from Park to 1st position, and then back to Park. If scan tool did not indicate correct gear shift positions, go to next step. If scan tool indicated correct gear positions, no problem is indicated at this time. Test is complete.
  3. Turn ignition off. Disconnect PCM connectors. PCM is located on firewall in right rear corner of engine compartment. Disconnect PNP connector. PNP is located on side of transmission. Inspect connectors for damaged pins, corrosion and loose terminals. Repair connectors as necessary. If connectors are okay, measure resistance of Brown/Light Blue wire between PNP harness connector and terminal A6 at PCM C1 harness connector. See Figure . If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in Brown/Light Blue wire.
  4. Measure resistance between ground and Brown/Light Blue wire at PNP harness connector. If resistance is 5 ohms or more, go to next step. If resistance is less than 5 ohms, repair short to ground in Brown/Light Blue wire between PNP and PCM.
  5. Reconnect PNP connector. Measure resistance between ground and terminal A6 (Brown/Light Blue wire) at PCM C1 harness connector while moving shift lever from Park to 1st position, and then back to Park. See Figure . If resistance does not change from less than 10 ohms to more than 10 ohms, replace PNP. If resistance changes from less than 10 ohms to more than 10 ohms, go to next step.
  6. At this time, PCM is assumed to be defective. Replace PCM.
  7. At this time, conditions for DTC to set do not exist or fault is an intermittent problem. Using scan tool, review FREEZE FRAME data and attempt to duplicate condition that caused DTC to set by paying special attention to DTC set conditions. Check for any related technical service bulletins that may apply. Visually inspect related connectors and wiring harness. Repair connectors and wiring harness as necessary. See WIRING DIAGRAMS article. If no problems are indicated, test is complete.
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