Transmission Range Switch Circuit Electrical 4.3L
Circuit Description
The transmission range (TR) switch is part of the park/neutral position (PNP) and back-up lamp switch assembly, which is externally mounted on the transmission manual shaft. The TR switch contains four internal switches that indicate the transmission gear range selector lever position. The VCM supplies ignition voltage to each switch circuit. As the gear range selector lever is moved, the state of each switch may change, causing the circuit to open or close. An open circuit or switch indicates a high voltage signal. A closed circuit or switch indicates a low voltage signal. The VCM detects the selected gear range by deciphering the combination of the voltage signals. The VCM compares the actual voltage combination of the switch signals to a TR switch combination chart stored in memory.
Diagnostic Aids
| • | Refer to the Transmission Range Switch Logic table for valid combinations of switch signal circuits A, B, C and Parity. On the table, HI indicates an ignition voltage signal. LOW indicates a zero voltage signal. |
| • | Inspect the connectors at the VCM, the TR switch and all other circuit connecting points for an intermittent condition. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
| • | Inspect the circuit wiring for an intermittent condition. Refer to Testing for Electrical Intermittents in Wiring Systems. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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By disconnecting the TR switch, the ground path of all TR switch circuits would be removed and the VCM would recognize all circuits as open.
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This step tests the TR switch wiring for an open or the lack of the signal voltage from the VCM.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 |
Does each selected transmission range match the Scan Tool TR Sw. display? | -- | Go to Diagnostic Aids | |
2 | Does the Scan Tool TR Sw. parameter display Invalid in every transmission range? | -- | ||
Does the Scan Tool TR Sw. parameter display Invalid? | -- | |||
Does the voltage measure within the specified value at all four terminals? | 10-12V | |||
5 | Test the signal circuit(s) (CKTs 771, 772, 773 and 776) of the TR switch for a shorted condition. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||
6 | Test the signal circuit(s) (CKTs 771, 772, 773 and 776) of the TR switch that did not indicate proper voltage for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||
7 | Test the ground circuit (CKT 451) of the TR switch for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||
8 | Replace the TR switch (this switch is part of the park/neutral position switch). Refer to Park/Neutral Position Switch Replacement . Did you complete the replacement? | -- | -- | |
9 | Replace the VCM. Refer to VCM Replacement/Programming (4.3L) in Engine Controls. Did you complete the replacement? | -- | -- | |
10 |
Does each selected transmission range match the Scan Tool TR Sw. display? | -- | System OK |
