Diagnostic Starting Point - Automatic Transmission Shift Lock Control
Begin the system diagnosis with the Diagnostic System Check - Vehicle in Vehicle DTC Information. The Diagnostic System Check 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 diagnostic trouble codes (DTCs) and their status
The use of the Diagnostic System Check 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 |
|---|---|---|
| Brake to Shift Control | Special Functions-Output Control | The BCM controls the voltage to the automatic transmission shift lock control solenoid ON or OFF for 5 seconds. |
Scan Tool Output Controls
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 | Data | 0-15 volts | 14 volts |
| Brake Applied Output | Outputs | ON/OFF | ON |
| BTSI Solenoid | Outputs | ON/OFF | OFF |
| Ignition 1 Signal | Outputs | ON/OFF | ON |
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. | |||
| Current Gear | Transmission Data | ||
| TR Sw. A/B/C/P | Transmission Data | Park, Park/Reverse, Reverse, Reverse/Neutral, Neutral, Neutral/Drive 4, Drive 4, Drive 4/Drive 3, Drive 3, Drive 3/Drive 2, Drive 2, Drive 2/Drive 1, Drive 1, Invalid, Open | |
| TCC Brake Switch | ON/OFF | OFF | |
Powertrain Control Module (PCM)
| 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. | |||
| Current Gear | Transmission Data | ||
| TR Sw. A/B/C/P | Transmission Data | Park, Park/Reverse, Reverse, Reverse/Neutral, Neutral, Neutral/Drive 4, Drive 4, Drive 4/Drive 3, Drive 3, Drive 3/Drive 2, Drive 2, Drive 2/Drive 1, Drive 1, Invalid, Open | |
| TCC Brake Switch | ON/OFF | OFF | |
Transmission Control Module (TCM)
Circuit Description
The body control module (BCM) controls the A/T shift lock control solenoid by providing battery voltage to the A/T shift lock control solenoid. The BCM utilizes a smart driver to control the voltage supplied to the A/T 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
Conditions for Running the DTC
- The ignition switch is in the ON position.
- The brake pedal is depressed.
- The transmission the PARK position.
Conditions for Setting the DTC
The BCM output driver detects an open or short in the output control circuit.
Action Taken When the DTC Sets
The BCM disables the output control until the next ignition 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
- Use a scan tool to verify there are no brake pedal position sensor and/or transmission internal mode switch (IMS) DTCs set that could cause the BCM not to provide battery voltage to the A/T shift lock control solenoid.
- If the automatic transmission shift lock control circuit is shorted to battery positive voltage, the A/T shift lock control solenoid will be inoperative. The vehicle will shift out of PARK without depressing 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-241671-S27410119602006081100000) .
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-241671-S33907418562006081100000) in Wiring Systems.
- 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-241731-S32839063942006081100000)
- «Shift Lever Can Be Moved without Brake Pedal Depressed»(ref-241731-S32513438222006081100000)