Toyota Shift Interlock System
SHIFT INTERLOCK SYSTEM. The shift lock system is designed to ensure the proper operation of the automatic transmission. The driver must depress the brake …
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SHIFT INTERLOCK SYSTEM
The shift lock system is designed to ensure the proper operation of the automatic transmission. The driver must depress the brake pedal in order to move the gear selector from Park to any other range. In addition, the ignition key cannot be turned to the Lock position and removed from the ignition switch unless the gear selector is placed in the Park position. There are three systems available in Toyota models; electrical, electrical/ mechanical and mechanical. We will not cover the application by model but rather by system type. For the specifics on a particular model, consult the repair manual.
Electrical Shift Lock Type
The electrical type uses electrical control of the shift lock mechanism, as well as the key lock mechanism. Shift Lock Mechanism The shift lock mechanism is made up of a number of components as seen in the illustration below.
The shift position switch (shift lock control switch) is used to detect the position of the shift lever. It has two contacts, P1 and P2. When the select lever is in the Park position, P1 is on (closed) and P2 is off (open). In this position, the key can be removed but the select lever is locked in position. When the select lever is in a position other than Park, P1 is off (open) and P2 is on (closed). In this position, the key cannot be removed. The grooved pin is part of the normal detent mechanism which requires that the shift lever button be depressed in order to move the gear selector into and out of Park position and also into Manual 2 or Manual Low positions. The shift lock plate is mounted next to the detent plate. In the Park position, the grooved pin fits into the slot at the top of the shift plate. The shift lock plate movement is limited by the plate stopper when the solenoid is not energized.
Shift Lock Override Button In order to move the shift lever out of Park, the ignition switch must be in the Accessory or ON position and the brake pedal must be depressed. When the brake pedal is depressed, the ECU turns on the solenoid, moving the plate stopper and allowing the shift lock plate to move down with the grooved pin. If the shift lock solenoid becomes inoperative, the shift lever cannot be moved and the vehicle cannot be moved. The shift lock override button can be used to release the plate stopper from the shift lock plate, releasing the shift lever so it can be moved from the Park position. Shift Lock ECU The ECU is generally found near the shift select lever. The shift lock system computer controls operation of the key lock solenoid and the shift lock solenoid based on signals from the shift position switch and the stop light switch.
Key Interlock System A camshaft is provided at the end of the key cylinder rotor. This camshaft has a cam with the cut-out portion of its stroke from the ACC position to the ON or Start position. The pin of the key lock solenoid protrudes out against the cam when the current is on and is pulled back by the return spring when the current is off. When the shift lever is shifted to a range other than the P range, current flows from the computer to the key lock solenoid, causing the pin to protrude out. If the key cylinder is turned with the pin in this position, it can be turned to the ACC position but cannot be turned further, due to the pin pushing against the cam. This prevents the key cylinder from being turned to the Lock position. The current to the key lock solenoid is cut off when the shift lever is shifted to the P range and the pin is pulled back by the return spring. This allows the key cylinder to be turned to the Lock position, and the key can be removed. Shift Lock System Computer The shift lock system computer controls operation of the key lock solenoid and the shift lock solenoid based on signals from the shift position switch and the stop fight switch. Key Lock Solenoid Control The shift position switch P2 is on (closed) when the shift lever is in a range other than the Park range. Current from the ACC and ON terminals of the ignition switch flows to Tr2 through the timer circuit. The base circuit of Tr2 is grounded by switch P2, and Tr2 goes on, energizing the key lock solenoid, preventing the key from going to the Lock position. The timer circuit cuts off the flow of current to Tr2 approximately one hour after the ignition switch is turned from ON to ACC, switching off the key lock solenoid. The timer circuit prevents the battery from being discharged. By placing the gear selector in the Park position, switch P2 is off (open), current no longer flows to the base of Tr2 and it goes off. The solenoid is no longer energized, and the solenoid plunger is retracted, and the key can be removed.
Shift Lock Solenoid Control When the shift lever is in the Park range, shift position switch P1 is on and the emitter circuit of Tr3 is grounded. Base current for Tr3 is provided through the stop light switch which is open while the brake is not applied, so Tr3 is off. Tr3 controls the base of Tr1, and as long as Tr3 is off, the shift lock solenoid will remain off and the gear selector will be locked in the Park position. When the brake pedal is depressed, the stop light switch goes on, providing current to the base of Tr3. When Tr3 goes on, base current flows in Tr1 and it then goes on, causing current to flow to the shift lock solenoid and freeing the shift lever. When the shift lever is shifted out of Park, the shift position switch P1 goes off and Tr1 switches the shift lock solenoid off.
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