Locks: Service and Repair
Key and Lock Cylinder Coding
Key Identification and Usage
The lock cylinder keyway is designed so that other model keys will not enter a current model lock cylinder. A single key is used for all locks on the vehicle.
The key identification is obtained from the four-character key code stamped on the knockout portion of the key head. Knock the plugs out of the key head after code numbers have been recorded. The code list, available to owners of key cutting equipment from equipment suppliers, determines the lock combinations from the code numbers.
Cutting Keys
After the code has been determined from the code list or the key code diagram, perform the following steps:
1. Cut a blank key to the proper level of each of the tumbler positions.
2. Inspect the key operation in the lock cylinder.
Replacement Lock Cylinders
New lock cylinders (except ignition lock cylinders) are available from the service parts warehouse with new lock cylinder locking bars. The tumblers are also available and must be assembled into the cylinder as recommended. For additional information, refer to the following.
Lock Cylinder Tumbler Operation
All lock tumblers are shaped alike with the exception of the notched position on one side. As the key is inserted into the lock cylinder, the tumblers are lowered to the correct height so that notches on each tumbler are at the same level. When the notches on all 6 tumblers line up, 2 small springs push the side bar into the notches, allowing the cylinder to turn in the cylinder bore. Five types of tumblers are used in making the lock combinations, and each is coded and stamped with a number between 1 and 5.
Assembling and Coding Ignition Lock Cylinders
Tools Required
J 41340 Ignition Lock Holding Fixture
1. Determine the tumbler numbers/arrangement:
1. Place the tip of the key directly over the tip of the illustrated key.
2. Inspect that the diagram outlines the key.
3. Starting with position 1 (open end of cylinder), find and record the lowest level (tumbler number) that is visible.
4. Repeat the previous step for positions 2-10.
2. Starting with position 1, insert the tumblers (4) into their corresponding slots in the coded order.
3. Using your fingers, pull out the side bar (3) until the tumblers fall completely into place.
4. Insert one tumbler spring (2) above each tumbler (4).
5. Lubricate the tumblers using Superlube(R) GM P/N 12346241 or equivalent.
6. Insert the spring retainer (1) prongs into the slots at the end of each cylinder.
7. Press down the retainer (1) until fully seated in the depression.
8. Inspect for proper tumbler installation:
1. Hold the spring retainer (2) in position.
2. Insert the key (1) into the cylinder.
3. The side bar (3) should drop down flush with the cylinder diameter if properly installed.
4. Disassemble and assemble properly as needed.
9. Remove the key.
10. Secure the cylinder in the J 41340.
1. Inspect that the spring retainer is facing up and positioned directly under the punch slots.
2. Push the cylinder into the J 41340 until butted with the cylinder bezel.
3. Tighten the holding screw.
11. Stake the bezel end of the retainer in place:
1. Hold the flat side of the punch, part of J 41340, squarely against the face of the cylinder bezel.
2. Stake the lock cylinder metal over the retainer corners.
12. Stake the other end of the retainer:
1. Remove the punch, part of J 41340.
2. Rotate the punch, part of J 41340, 180 degrees.
3. Hold the punch, part of J 41340, squarely against the end of the punch slot on J 41340.
4. Stake the metal over the other end of the retainer.
13. Loosen the holding screw.
14. Remove the cylinder from the J 41340.
15. Inspect that the retainer is properly staked. Restake as needed.
16. Lubricate the cylinder retainer slot.
17. Insert the following parts into the cylinder retainer slot:
* The retainer spring (2)
* The retainer (3)
Important: Use a paste type grease, not a spray, for the following step.
18. Lubricate the following parts with GM P/N 12345996 or equivalent as needed:
* The detent pins (1)
* The cylinder retainer (3)
Endgate and Front Side Door Lock Cylinder Coding
The endgate and front side door lock cylinder uses 8 of the 10 key cut positions, 3-10 when counting from the key head. The tumbler orientations alternate in adjacent locations from side with 4 each side.
Important: The front side door lock cylinder tumblers (3) are not self-retaining and must be held in place if the key is not fully inserted into the lock cylinder or until the rotor (1) is assembled into the rotor case (4).
1. Hold the uncoded rotor (1) positioned so the side of the rotational stop lug is facing downward, as shown.
2. Insert one tumbler spring (2) each into the 4 holes from the upper side.
3. The first tumbler to be loaded will be key cut position number 3, the third number in the key code. Determine the cut depth at this position and install the corresponding tumbler (3) into the tumbler slot nearest the front of the rotor-CP.
4. In the same manner, determine the cut depth and corresponding tumbler and install the 3 remaining tumblers (3) into the tumbler slots located at key cut positions 5, 7, and 9.
5. Check for correct loading by holding the tumblers (3) in position and fully inserting the matching key into the rotor. All tumblers should be flush with the outside diameter of the rotor.
6. Rotate the rotor (1) so that the side with the rotational stop lug is facing upward and then remove the matching key. Remember the tumblers (3) are not self-retaining and must be held in place.
7. Insert one tumbler spring (2) each into the 4 tumbler spring holes.
8. The first tumbler to be loaded will be key cut position number 4. Determine the cut depth at this position and install the corresponding tumbler (3) into the tumbler slot nearest the front of the rotor-CP.
9. In the same manner, determine the cut depth and corresponding tumbler and install the 3 remaining tumblers (3) into the tumbler slots located at key cut positions 6, 8, and 10.
10. Check for correct loading by holding the tumblers (3) in position and fully inserting the matching key into the rotor (1). All tumblers should be flush with the outside diameter of the rotor.
11. Lightly lubricate tumbler (3) and rotor (1) surfaces using the lubrication provided.
12. With the matching key fully inserted into coded rotor, install the coded rotor into the rotor case (4) fully. Make sure rotor is stopped at approximately 60 degrees when you rotate to clockwise and counterclockwise with the key, approximately 120 degrees total.
13. Remove the key, the rotor stays in the rotor case, and install the lock cylinder cap (5) on the rotor case (4). Crimp the side edge of the lock cylinder cap (5) around the rotor case depressions, 2 places.
14. For endgate cylinders, proceed to step 16. For door lock cylinders, hold the cylinder assembly so the key opening is facing down, 6 o'clock, and the cylinder cut out is facing you, so tumblers are visible. Slide the return spring (6) around the rotor top, 12 o'clock position. The return spring (6) resides between the rotor and rotor case.
15. Keep the cylinder assembly in the same orientation, key opening at 6 o'clock and rotor top at 12 o'clock. The return spring consists of a lower and upper spring tab. Locate the lower spring to the left side of the cylinder tab. This cylinder tab is located at the 12 o'clock position and resembles a hook shape. No force is required against spring tension. Then, working against spring tension, rotate the upper spring tab to the right side of the cylinder tab. The upper spring tab will finally reside in the hook shape of the cylinder tab.
16. Keep the cylinder assembly in the same orientation, key opening at 6 o'clock and rotor top at 12 o'clock. Orient lever (7) with tab at facing down at 6 o'clock. Lower the lever (7) onto the rotor top so the tab fits between spring tab upper and spring tab lower.
17. Install the retaining ring (8) in the groove at the end of the rotor (1) to secure the lever (7) to the cylinder. Concave surface of retaining ring (8) should touch the lever.
18. Install the clip (9) as shown.