For 1990-2009 cars

### Circuit Description

The TCM also communicates the park/neutral switch status to the BCM via serial data. The BCM uses this data to control the Electronic PRNDL display on the shifter. The BCM controls the LED's in the PRNDL display through 4 control circuits. The BCM has 8 DTCs for these 4 control circuits. These DTCs diagnose a shorted or an open for each circuit.

### Diagnostic Aids

Refer to Transmission Range Switch Logic for valid combinations of switch signal circuits A, B, C and P.

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. By disconnecting the TR switch, the voltage path for all TR switch circuits would be removed and the TCM should recognize all circuits as open. The scan tool should display LOW for all range signals.

2. This step tests the TR switch wiring for an open or lack of ground from the TCM.

3. This step tests the TR switch wiring and the TCM by providing a voltage path through a fused jumper wire. When jumpered, the scan tool range signal A should change to HI.

4. This step tests the TR switch wiring and the TCM by providing a voltage path through a fused jumper wire. When jumpered, the scan tool range signal B should change to HI.

5. This step tests the TR switch wiring and the TCM by providing a voltage path through a fused jumper wire. When jumpered, the scan tool range signal C should change to HI.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
1 |

1. Install a scan tool.
2. Turn ON the ignition, with the engine OFF.
3. Select TR Sw. on the scan tool.
4. With the scan tool, observe the TR Sw. display while selecting each transmission range: P, R, N, D, I and L.

Does each selected transmission range match the scan tool TR Sw. display?

--

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 2

2 |

1. Inspect the TR switch for the following:

• | Damage

• | Loose or missing mounting hardware

• | Refer to Transmission Range Switch Replacement .

• | Proper adjustment

• | Refer to Transmission Range Switch Adjustment .

2. Inspect the shift cable for the following:

• | Damaged or stretched cable

• | Proper adjustment

• | Refer to Transmission Control Replacement .

Did you find and correct a condition?

--

Go to Step 15

Go to Step 3

3 | With the scan tool, observe the TR Sw. A/B/C/P display. Does the scan tool TR Sw. A/B/C/P parameter indicate LOW for all range signal states? | -- | Go to Step 12 | Go to Step 4
4 |

1. Turn OFF the ignition.
2. Disconnect the TR switch 10-way connector.
3. Turn ON the ignition, with the engine OFF.

Does the scan tool TR Sw. A/B/C/P parameter indicate LOW for all range signal states?

--

Go to Step 5

Go to Step 9

5 |

1. Using the digital multimeter (DMM) and the J 35616 GM terminal test kit, measure the voltage from terminal 10 of the TR switch 10-way connector to ground.
2. Measure the voltage from terminal 6 of the TR switch 10-way connector to B+.
3. Measure the voltage from terminal 5 of the TR switch 10-way connector to B+.
4. Measure the voltage from terminal 8 of the TR switch 10-way connector to B+.

Does the voltage measure within the specified range at all four terminals?

10-12 V

Go to Step 6

Go to Step 10

6 | Connect a fused jumper wire from terminal 10 of the TR switch 10-way connector, signal A circuit, to B+ while monitoring the scan tool TR Sw. A/B/C/P parameter. When the signal A circuit is jumpered, do any other signal circuits indicate HI? | -- | Go to Step 11 | Go to Step 7
7 | Connect a fused jumper wire from terminal 6 of the TR switch 10-way connector, signal B circuit, to B+ while monitoring the scan tool TR Sw. A/B/C/P parameter. When the signal B circuit is jumpered, do any other signal circuits indicate HI? | -- | Go to Step 11 | Go to Step 8
8 | Connect a fused jumper wire from terminal 5 of the TR switch 10-way connector, signal C circuit, to B+ while monitoring the scan tool TR Sw. A/B/C/P parameter. When the signal C circuit is jumpered, do any other signal circuits indicate HI? | -- | Go to Step 11 | Go to Step 13
9 | Test the signal circuit or circuits of the TR switch that did not indicate LOW for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 14
10 | Test the signal circuit or circuits of the TR switch that did not indicate proper voltage for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 14
11 | Test the affected signal circuits of the TR switch for a shorted together condition. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 14
12 | Test the voltage supply circuit of the TR switch for an open or short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 13
13 | Replace the TR switch. Refer to Transmission Range Switch Replacement . Did you complete the replacement? | -- | Go to Step 15 | --
14 | Replace the TCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 15 | --
15 |

1. Turn ON the ignition, with the engine OFF.
2. With the scan tool, observe the TR Sw. display while selecting each transmission range: P, R, N, D, I and L.

Does each selected transmission range match the scan tool TR Sw. display?

--

System OK

Go to Step 2