GM Service Manual Online
For 1990-2009 cars only

Special Tools

    • EN-48749 Timing Chain Retention Tool Kit
    • EN-48953 Camshaft Actuator Locking Tool
    • J 45059 Angle Meter

Removal Procedure


    Object Number: 1578296  Size: SH
  1. Remove the camshaft cover. Refer to Camshaft Cover Replacement.
  2. Remove the upper timing chain guide bolts and guide.

  3. Object Number: 2134128  Size: SH
  4. Install a 24 mm wrench onto the hex on the camshaft in order to rotate the camshafts clockwise and install the camshaft actuator retainer EN-48953 (1).
  5. Notice: Refer to Fastener Notice in the Preface section.

  6. Install the camshaft actuator retainer bolts.
  7. Tighten
    Tighten the bolts to 10 N·m (89 lb in).

  8. Loosen, but do not remove the intake and exhaust camshaft actuator bolts.
  9. Important: Ensure the timing chain and the camshaft position actuators are marked for proper assembly.

  10. Mark the intake and exhaust camshaft actuators and the respective locations on the timing chain.

  11. Object Number: 1578295  Size: SH
  12. Remove the timing chain tensioner.

  13. Object Number: 2066482  Size: SH

    Important: The camshaft actuators should not rotate during the removal or installation.

    Important: Ensure the tips of the EN-48749 are fully engaged into the timing chain. The retention tool rod can be used on the back side of the chain to ensure the teeth from the retention tool are engaged.

  14. Install the timing chain retention tool EN-48749 (1) to the exhaust side of the timing chain.

  15. Object Number: 1578298  Size: SH
  16. Remove and discard the exhaust camshaft actuator bolt (2).
  17. Remove the exhaust camshaft actuator (3) from the camshaft while also removing the actuator from the timing chain.

Installation Procedure


    Object Number: 1578298  Size: SH

    Important: Ensure that the alignment mark made previously on the intake camshaft actuator is still aligned properly with the mark on the timing chain.

    Important: The exhaust camshaft may need to be rotated clockwise to fully set the camshaft actuator.

  1. Install the timing chain onto the exhaust camshaft actuator.
  2. Align the exhaust camshaft actuator alignment mark made previously with the timing chain mark and install the actuator onto the camshaft.
  3. Install a NEW exhaust camshaft actuator bolt (2) until snug.

  4. Object Number: 2066482  Size: SH
  5. Remove the timing chain retention tool EN-48749 (1) from the exhaust side of the timing chain.
  6. Reset and install the timing chain tensioner. Refer to Timing Chain Tensioner Replacement.

  7. Object Number: 2134128  Size: SH
  8. Install the camshaft actuator retainer (1).
  9. Install the camshaft actuator retainer bolts.
  10. Tighten
    Tighten the bolts to 10 N·m (89 lb in).


    Object Number: 1673556  Size: SH
  11. Remove the tool (1) from the exhaust camshaft side of the timing chain assembly.
  12. Install a 24 mm wrench onto the hex on the camshaft in order to hold the camshaft.
  13. Tighten the NEW camshaft actuator bolt.
  14. Tighten
    Tighten the bolt to 85 N·m (63 lb ft), plus an additional 30 degrees using the J 45059 .

    Important: You must have the EN-48953 installed to perform this procedure.

  15. Release the tensioner by rotating the crankshaft balancer counterclockwise and tighten the bolt.
  16. Tighten
    Tighten the bolt to 45 N·m (33 lb ft).


    Object Number: 2066456  Size: SH
  17. Remove the camshaft actuator retainer EN-48953 (1).

  18. Object Number: 1578296  Size: SH
  19. Install the upper timing chain guide and bolts.
  20. Tighten
    Tighten the bolts to 10 N·m (89 lb in).

  21. Install the camshaft cover. Refer to Camshaft Cover Replacement.