E174

DESCRIPTION
The Park/Neutral switch is a part of the transmission Gear Selector Switch. Pin "A" of the six way weather pack connector on the switch is the park/neutral input for the ECM. The Park/Neutral Switch contacts are closed in park or neutral, shorting switch Pin "A" to ground. In any other gear range, Pin "A" is open.
The ECM sends 12 volts to Pin "A" of the Gear Selector Switch on CKT 434. when the gear selector is in park or neutral, the 12 volt signal from the ECM is shorted to ground, resulting in 0 volts at ECM Pin "A2".
On the diagnostic display, "HI" is an open switch indication (not in park or neutral) and "LO" is a closed switch (gear selector in park or neutral).
The ECM uses Park/Neutral status for fuel and idle speed control and as a test condition for many trouble codes.

Notes on Fault Tree
1. Status "HI" at all times means that CKT 434 12 volt supply from ECM Pin A2 is never being shorted to ground in park or neutral.
2. Status "LO" at all times means that CKT 434 12 volt supply from ECM Pin A2 is shorted to ground in all gear selector ranges.

Notes on Intermittents
Check for trans gear selector switch out of adjustment. Check for trans shift indicator out of adjustment. Check for intermittent open or short to ground in CKT 434 between ECM and switch.