Circuit Description
The transmission range switch is a multi-signal switch which sends a signal to the powertrain control module (PCM) to indicate gear selection. The transmission range switch uses 4 discrete circuits to pull 4 PCM voltages low in various combinations to indicate each gear range. The voltage level of the circuits is represented as LOW = grounded, HIGH = open circuit. The 4 states displayed represent decoder P, A, B, and C inputs in sequence.
Conditions for Setting
| • | The PCM recognizes an invalid PRNDL parameter. |
| • | The vehicle speed is greater than 5 mph. |
| • | The above conditions are met for greater than 5 seconds. |
Action Taken
The transmission will default to 3rd gear.
Conditions for Clearing the MIL/DTC
| • | A history DTC will clear after 40 consecutive ignition cycles have occurred without a fault. |
| • | History and current DTC can be cleared by using a scan tool. |
Diagnostic Aids
| • | Monitor a scan tool while moving related connectors and wiring harness. If a failure is induced, the scan data will change states from either LOW to HIGH, or from HIGH to LOW. Moving the gear selector slowly through each gear while monitoring the scan tool may also help isolate the problem. |
| • | If the trans range switch on the scan tool and the PRNDL on the IPC read only in. |
| • | Park, 1st, and 2nd gear check for an open CKT 772. |
| • | Reverse, Neutral, 4th, and 3rd gear check for a grounded CKT 772. |
| • | 1st, 2nd, 3rd, and 4th gear check for a grounded CKT 773. |
| • | Park, Reverse, and Neutral check for an open CKT 773. |
| • | Park, Reverse, 2nd, 3rd gear check for a grounded CKT 771. |
| • | Neutral, 4th and 1st gear check for an open in CKT 771. |
| • | Park, Neutral, 3rd, and 1st gear check for a grounded CKT 776. |
| • | Reverse, 2nd, and 4th gear check for an open CKT 776. |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Was the On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | |
2 |
Do the PRNDL encoded values match the value column? | P-LOW A-LOW B-HIGH C-HIGH | Go to Step 3 | Go to Step 4 |
Compare the scan tool value in each gear select position to the chart on the facing page. Are all combinations correct? | -- | Go to Diagnostic Aids | Go to Step 8 | |
4 | Does the PRNDL encoded value on the scan tool match the value column? | P-HIGH A-HIGH B-HIGH C-HIGH | Go to Step 9 | Go to Step 5 |
5 | Does the PRNDL encoded value on the scan tool match the value column? | P-LOW A-LOW B-LOW C-LOW | Go to Step 6 | Go to Step 7 |
6 | Disconnect the powertrain control module (PCM) connector at the PCM. Does the PRNDL encoded value on the scan tool match the value column? | P-HIGH A-HIGH B-HIGH C-HIGH | Go to Step 12 | Go to Step 11 |
7 |
Is the action compete? | -- | -- | |
8 |
Is the action complete? | -- | -- | |
9 |
Was an open circuit found? | -- | Go to Step 10 | |
10 | Replace the trans range switch. Is the action complete? | -- | -- | |
11 | Replace the PCM. Is the action complete? | -- | -- | |
12 |
Was a grounded PRNDL input wire found? | -- | Go to Step 10 | |
