Description

DATA TROUBLE CODE: P1780

SYSTEM: Park/Neutral Position Switch Malfunction

CIRCUIT DESCRIPTION
The park/neutral position switch goes on when the shift lever is in the N or P shift position. When it goes on terminal NSW of the Engine Control Module is grounded to body ground via the starter relay thus the terminal NSW voltage becomes 0.0 volts. When the shift lever is in the D, 2, L or R position, the park/neutral position switch goes off, so the voltage of Engine Control Module terminal NSW becomes battery voltage, the voltage of the Engine Control Module internal power source.
If the shift lever is moved from the N position to the D position, this signal is used for air-fuel ratio correction and for idle speed control (estimated control), etc.

DIAGNOSTIC TROUBLE CODE DETECTING CONDITION
- Two or more switches are ON simultaneously for "N", "2" and "L" position (2 trip detection logic).
- When driving under conditions below for 30 seconds or more the park/neutral position switch is ON (N position) (2 trip detection logic).
- Vehicle speed: 70 km/h (44 mph) or more.
- Engine speed: 1,500 - 2,500 rpm.

TROUBLE AREA
- Short in park/neutral position switch circuit.
- Park/neutral position switch.
- Engine Control Module.

NOTE: After confirming Diagnostic Trouble Code P1780 use the LEXUS hand-held tester to confirm the PNP switch signal from "CURRENT DATA".