P091

DTC PO91: Part 1 Of 2:

DTC PO91: Part 2 Of 2:

Transaxle Range Switch Circuit:

DESCRIPTION
This diagnostic test monitors the binary code generated by the four input switches of the transaxle range switch. If any one of the following conditions happen Code P091 will set.

1. Any 4 digit code that does not match one of the codes in the chart in the accompanying image for 64 seconds.
2. Engine start while Code 1100 (PARK) or 1010 (NEUTRAL) not present.
3. Powertrain Control Module (PCM) commanding 4th gear and the ratio of engine speed (RPM) to vehicle speed indicating 4th gear achieved with a PARK (1100) or NEUTRAL (1010) code for 64 seconds.

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 Transaxle Range Switch provides a parity input that gives an even number of 1's per the table in the accompanying image, if the switch and circuit are working properly.

TEST CONDITIONS
Test continuously.

FAILURE CONDITIONS
1. Any 4 digit code that does not match one of the codes in the above chart for 64 seconds.
2. Engine start while code 1100 (PARK) or 1010 (NEUTRAL) not present.
3. PCM commanding 4th gear and the ratio of engine speed/vehicle speed indicating 4th gear achieved with a PARK (1100) or NEUTRAL (1010) code.

ACTION TAKEN
1. PCM turns "ON" the "SERVICE VEHICLE SOON" Malfunction Indicator Lamp (MIL).
2. PCM disables cruise control.

NOTES ON INTERMITTENTS
The PCM code snapshot provides valuable information in diagnosing an intermittent Code P091. If all digits of PD71 and PD72 are 1, then check for an intermittent loss of ground to the transaxle range switch. If an intermittent Code P091 occurs when the transaxle shift lever is moved, the code is most likely caused by a misadjustment of the shift linkage or Transaxle range switch, causing the Transaxle range switch to end up in the range between gears.

On the other hand, if the code occurs and the Service Engine Soon vehicle comes on while driving or when the driver is not moving the gear selector lever, record PD71 and PD72 and compare the values to the chart. For example, if the driver was driving in "OD" when the message came on and PD71 reads 10 and PD72 reads 11, check for an intermittent open in CKT 773. Manipulate related wiring and connectors while observing parameters PD71 and PD72 (or scan tool display). If an intermittent is induced, the digit corresponding to that circuit will change. If wiring and connectors check out OK, substitute a known good transaxle range switch and recheck.