Diagnosis & Repair

Disconnect PNP switch connector. PNP switch is located at transmission where shifter select cable is mounted. Using ohmmeter, check continuity of switch terminals in specified positions. See Fig 1 and Fig 2. Replace switch as necessary.
If switch is okay, access ECM behind glove box. Turn ignition on. Using DVOM, measure voltage between ground and terminal No. 2 (Black wire) at ECM E7 connector. See Figure.
Voltage should be 0-3 volts in "P" or "N" position. Voltage should be 9-14 volts in any other shift selector position. If all voltages measured are as specified, replace ECM and retest.
If any voltage is not as specified, check for an open or short in wiring harness between PNP switch and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.

Fig 1: Identifying PNP Switch Terminals

Fig 2: PNP Switch Continuity Chart