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Home >> Toyota >> 2003 >> Highlander Limited, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 52 (Automatic Transmission Diagnosis - U140E & U140F) >> Diagnostic Tests >> DTC P1780: Park/Neutral Position Switch Circuit Malfunction (RX 300) >> Diagnostic Procedure

Diagnostic Procedure

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  1. Install scan tool to DLC3. Turn ignition on. Monitor PNP switch function. Move the gearshift lever through all gear ranges, while observing the scan tool. See Fig 1. If the readings are within specification, check for intermittent condition: Loose terminal tension, corroded terminals, cut or broken wiring or chaffed wiring harness and repair as necessary. If readings are not within specification, go to step  3.
  2. Turn ignition on. Measure voltage between ground and terminals NSW, "2", "L" and "R" of ECM, while the gearshift lever is moved through all positions. See Fig 2. If voltage is not as specified, go to next step. If voltage is as specified, replace ECM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE.
  3. Raise and support vehicle. Remove the PNP switch. Check for continuity between each terminal shown when the gearshift lever is moved into each position. See Figure and Figure . If continuity is not within specification, replace the PNP switch. If continuity is within specification, go to next step.
  4. Check wiring harness and connector between battery and PNP switch, and from PNP switch to ECM. If problem was found, replace wiring harness and connector. If no problem was found, replace ECM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE.
Fig 1: Identifying Scan Tool Gearshift Position Signal Values
G00115726Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
Fig 2: Measuring ECM Voltages From PNP Switch
G00115727Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002