E91 Part 1 of 2

Diagnostic Chart.:

Wiring Diagram.:

DESCRIPTION:

This diagnostic test monitors the binary code generated by the four input switches of the PRNDL switch.
If a code generated by these switches is not recognized by the PCM, the code will set.

TEST CONDITIONS:

Continuous.

FAILURE CONDITIONS:

1. An open or short to ground in one or more switches or circuits that would generate an invalid binary code.
2. An engine start with a code recognized by the PCM as one for a forward or reverse gear.

ACTION TAKEN:

1. Code is set.
2. PCM turns on SERVICE ENGINE SOON lamp.

NOTE ON DIAGNOSIS:

The PCM data displays, P.2.2 and P.2.3 and indicates the status of each of the four circuits. A pull up resistor produces a battery voltage signal at the PCM terminal when the circuit is open and no signal when the circuit is to ground. The switches A, B, and C produce circuit signals in a set pattern, and switch P provides parity with an alternating closed and open signal. The parity input provides a check of proper operation, since the PRNDL switch provides a parity input that gives an even number of 1's per the table above, if the switch and circuit are working properly.

PCM VOLTAGE CHECK

PCM TERMINAL SWITCH OPEN SWITCH CLOSED

F8 0 TO 0.3 BATTERY VOLTS

C10 0 TO 0.3 BATTERY VOLTS

F7 0 TO 0.3 BATTERY VOLTS

A2 0 TO 0.3 BATTERY VOLTS