P1520

Transaxle Range Switch Valid Input Combinations:

Circuit Description

This vehicle uses an electronic gear indicator display. There are four inputs which are switches to ground that each have a unique switch pattern. All four of these inputs are housed in the PNP switch assembly and operate together as the Transaxle Range Switch. The PCM uses the combination of the switch patterns to determine the gear selected by the driver. This information is then sent by serial data to the Instrument Panel Cluster (IPC) for gear indicator display. This diagnostic test monitors the transaxle range switch for false outputs. The DTC will set if the transaxle range switch is indicating a switch pattern that the PCM does not recognize.

Conditions for Running the DTC

^ Tested continuously.
^ DTCs P0502 or P0503 not set.

Conditions for Setting the DTC

Transaxle range switch indicating an illegal combination for 3.3 seconds

Action Taken When the DTC Sets

PCM will substitute park/neutral status from the Transaxle Fluid Pressure (TFP) switch for vehicle park/neutral status.

^ The Malfunction Indicator Lamp (MIL) will not illuminate.
^ The PCM will command a message to be displayed.
^ The PCM may record operating conditions at the time the diagnostic fails. This information will be stored in the Failure Records.

Conditions for Clearing the Message/DTC

^ The PCM will turn the message OFF after one run and pass of the diagnostic test.
^ A History DTC will clear after forty consecutive warm-up cycles with no failures of any non-emission related diagnostic test.
^ A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.
^ Use a scan tool to clear DTCs.
^ Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended.

Diagnostic Aids

Important: Check shifter for normal freedom of movement.

The gear select display will box all gear indications and flash on and off if an invalid or suspect gear position is received by the PCM. This will normally occur if the gear selector is not fully in a gear position. When a valid gear position is attained, the gear select display will immediately display the correct position. If the PRNDL on the IPC is flashing, this may be an indication that the shift cable and/or Transaxle Range Switch is out of adjustment.

^ The modes (circuits) are displayed in order A/B/C/P.
^ L indicates the circuit low (switched / shorted to ground).
^ H indicates the circuit is high (open).
^ If the DTC sets and the PRNDL on the IPC is flashing while driving or when the driver in not moving the gear selector lever, record the transaxle range switch input and compare the values to the table. For example, if the vehicle was operating in overdrive when the PRNDL on the IPC flashed and the input read High, Low, High, High, check for an intermittent open in circuit 773.
^ Manipulate related wiring and connectors while observing the transaxle range switch input. If an intermittent is induced, the digit corresponding to the circuit will change. If wiring and connectors check out OK, substitute a known good transaxle range switch and recheck.

Depending on the Scan Tool used, the transmission fluid pressure switch parameter and the gear select lever parameter may have two different titles. For example: when using a Tech 1 on a 1996 vehicle the gear select lever parameter would be named Sel. Lever Sw. and Sel. Lever Sw. A/B/C/P. The same vehicle and parameter using a Tech 2 would be named Transmission Range and T R Switch A/B/C/P. These same parameters may also call the state of the circuit differently. For example: the Tech 1 may indicate ON for an open circuit while the Tech 2 would indicate High for an open circuit. Proper verification of the parameter being observed can be indicated by the inability of the transmission fluid pressure switch to indicate any gear other than Drive 2 when the vehicle is not running (no pressure available).

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

2. The adjustment procedures must be done before diagnosis of the system. This step does a comparison of both the transaxle range switch and the transaxle pressure switches. If both displays match in all gear selections then the fault is not present or may have been repaired when the adjustment procedures were performed.
3. The engine must be running in order to obtain gear indications from the TFP switch.
If the TFP Switch display doesn't match the gear selected then the transaxle pressure switches are at fault.
4. Checking if the ground circuit to the switch may be at fault.
5. If a circuit stays High or Low all the time, that circuit or switch is open or shorted to ground.