Diagnostic Starting Point - Automatic Transmission Shift Lock Control
Begin the system diagnosis with Diagnostic System Check - Vehicle . The Diagnostic System Check - Vehicle will provide the following information
- The identification of the control modules which command the system
- The ability of the control modules to communicate through the serial data circuit
- The identification of any stored DTCs and their status
The use of the Diagnostic System Check - Vehicle will identify the correct procedure for diagnosing the system and where the procedure is located.
Scan Tool Output Controls
| Scan Tool Output Control | Additional Menu Selection(s) | Description |
|---|---|---|
| Shift Lock Solenoid | Special Functions, BCM, Miscellaneous Test | Command supplies battery voltage to the A/T shift lock control circuit ON or OFF for 5 seconds. |
Body Control Module (BCM)
Scan Tool Data List
| Scan Tool Parameter | Data List | Units Displayed | Typical Data Value |
|---|---|---|---|
| Operating Conditions: Ignition ON, with the engine OFF. Transmission shift lever in the PARK position. Brake pedal released. | |||
| Battery Voltage | BCM, Data Display, Charging Info | Volts | 12.9 Volts |
| Shift Lock Solenoid Command | BCM, Data Display, Outputs | ON/OFF | OFF |
Body Control Module (BCM)
| Scan Tool Parameter | Data List | Units Displayed | Typical Data Value |
|---|---|---|---|
| Operating Conditions: Ignition ON, with the engine OFF. Transmission shift lever in the PARK position. Brake pedal released. | |||
| BPP Circuit Signal | ECM, Electrical/Theft Data | Applied/Released | Released |
Engine Control Module (ECM)
| Scan Tool Parameter | Data List | Units Displayed | Typical Data Value |
|---|---|---|---|
| Operating Conditions: Ignition ON, with the engine OFF. Transmission shift lever in the PARK position. Brake pedal released. | |||
| TR Sw. | Transmission Data | Park, Reverse, Neutral, Drive 5, Drive 4, Drive 3, Drive 2, Drive | Park |
Transmission Control Module (TCM) 4.8L, 5.3L and 6.0L
| Scan Tool Parameter | Data List | Units Displayed | Typical Data Value |
|---|---|---|---|
| Operating Conditions: Ignition ON, with the engine OFF. Transmission shift lever in the PARK position. Brake pedal released. | |||
| IMS | Transmission Data | Invalid, Drive 2, Reverse\Neutral, Neutral, Drive 6, Neutral\Drive 6, Park, Drive 3, Reverse, Park\Reverse, Drive 4 | Park |
Transmission Control Module (TCM) 6.2L
Circuit Description
The body control module (BCM) controls the automatic transmission shift lock control solenoid by providing a battery positive voltage to the solenoid. The BCM utilizes a smart driver to control the voltage supply circuit to the automatic transmission shift lock control solenoid. The smart driver monitors the voltage and current flow of the control circuit.
DTC Descriptor
This diagnostic procedure supports the following DTC
DTC B2705 Gearshift Unlock Circuit
| DTC Symptom | DTC Symptom Descriptor |
|---|---|
| 02 | Short to Ground |
DTC B2705
Conditions for Running the DTC
- The ignition switch is in the ON position.
- The brake pedal is pressed.
- The transmission is in the PARK position.
Conditions for Setting the DTC
Sets if there is a short to ground in the automatic transmission shift lock control solenoid control circuit
Action Taken When the DTC Sets
The BCM will not attempt to enable the voltage supply circuit of the automatic transmission shift lock control solenoid until the next key cycle.
Conditions for Clearing the DTC
- A current DTC B2705 will clear when the malfunction is no longer present and the ignition switch is cycled.
- All BCM history codes will clear after 100 ignition cycles with no current codes active during the 100 ignition cycles.
Diagnostic Aids
- If the automatic transmission shift lock control circuit is shorted to ground, the automatic transmission shift lock control solenoid will be inoperative. The vehicle will shift out of PARK without pressing the brake pedal.
- Perform the tests while wiggling the wires and connectors. This may often cause an intermittent malfunction to appear. Refer to «Testing for Intermittent Conditions and Poor Connections»(ref-278019-S21810776732008012100000) .
Visual/Physical Inspection
- Inspect for aftermarket devices which could affect the operation of the automatic transmission shift lock control. Refer to «Checking Aftermarket Accessories»(ref-278019-S10639375482008012100000) .
- Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
Symptom List
Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom
- «Shift Lever Does Not Move with Brake Pedal Depressed»(ref-278062-S09182086802008012100000)
- «Shift Lever Can Be Moved without Brake Pedal Depressed»(ref-278062-S11231418162008012100000)