P091

Diagnostic Trouble Code P091:

Transaxle Range Switch:

CIRCUIT DESCRIPTION
This diagnostic test monitors the PARK/NEUTRAL position switch for it to be closed when the vehicle is in gear or an engine start while the PARK/NEUTRAL position switch is open (not in P/N).

TEST CONDITIONS
1. Vehicle speed = 0
2. Gear ratio indicating P/N range.

FAILURE CONDITIONS
Test 1
^ Engine speed changes from zero to non-zero without the PARK/NEUTRAL input to the Powertrain Control Module (PCM) "HI" (not in P/N).
^ At least 5 seconds have past since a transition of the PARK/NEUTRAL position switch.
Test 2
^ Codes P024, P075 and P086 not set.
^ PARK/NEUTRAL input to the PCM "LO" (in P/N).
^ Engine running.
^ Throttle position 15.7 degrees or greater.
^ Vehicle speed 7 mph or greater.
^ Gear ratio of 3.11 or less (vehicle in gear).
^ All conditions true for 5 seconds.

ACTION TAKEN
1. PCM turns "ON" the "Service Vehicle Soon" message.
2. PCM disables cruise control.
3. PCM will substitute gear status from transaxle pressure switch for PARK/NEUTRAL position switch.

NOTES ON FAULT TREE:
1. Checking PCM status light. "AUTO" should be "ON" when gearshift is in PARK/NEUTRAL and "OFF" in any other gear position.
2. Checking PARK/NEUTRAL position switch for an open.
3. Checking CKT 451 for an open.
4. Checking CKT 434 for an open.
5. Checking if fault is still present.
6. Checking for a shorted PARK/NEUTRAL position switch.
7. Checking CKT 434 for a short to ground.

NOTES ON INTERMITTENTS:
1. Check for an intermittent short to ground on CKT 434.
2. A stall or near stall condition which may set Codes P054 or P095 may cause Code P091 to set falsely. This is because the engine will transition from running to not running (or near stall) and then back to running without the transaxle range switch being in PARK or NEUTRAL.