GM Service Manual Online
For 1990-2009 cars only

The vehicle's cargo area can be used in many different configurations--cargo panels on or off, Midgate® up or down, rear glass in or out. It has features that resist the elements and protect cargo. It is designed to quickly direct water out of the cargo box. The top drain grates, side rail channels, catch cups, Midgate® drain, cargo area floor drains and the rubber cargo mat help do this.

Even when all of these things are working properly and the cover system is on, there may be some instances (heavy rains, automated car washes, etc.) when water can collect the following areas:


  1. Object Number: 814326  Size: B4

    Top drain grates

  2. Removable front drain grate (Midgate® drain gate)

  3. Side rail channels and catch cups

  4. Front drains

  5. Water drainage area around both sides of the box and the tailgate side

  6. Rear drains

  7. Cargo floor

  8. Cargo mat

Maintenance and Cleaning

To ensure that the water management system performs properly, be sure that the Midgate®, tailgate and cover system are fully closed and that all parts are clean and not blocked with debris. Follow the instructions given next in this section for the proper procedures on cleaning each item.

Top Drain Grates - Removal and Cleaning


Object Number: 805550  Size: B3

The top drain grates are located near the rear window on both sides of the vehicle. Clean the grates and drains if there is a blockage.

To remove each drain grate, do the following:

  1. Remove the cargo panels or tonneau cover. See Cargo Cover Panels or Tonneau Cover for more information.

  2. Object Number: 805551  Size: B3
  3. Grasp the edges of the grate and pull it out from the vehicle. Flush the drain with clean water.

To replace the drain grate:


    Object Number: 805552  Size: B3
  1. Line up the clips on the vehicle with the slots in the grate and firmly push the grate down.

Do not force the grate. If it does not clip into place, realign the clips with the holes and try again.

Side Rail Channels


Object Number: 806972  Size: B3

The side rail channels are located on top of both sides of the cargo area. Flush them out with clean water if debris collects inside of them.

Carefully load cargo into the cargo area, so that the rails do not get damaged.

Midgate® Drain Grate Removal and Cleaning


Object Number: 805553  Size: B3

The removable Midgate drain grate is located near the base of the Midgate.

After hauling dirt, wood chips, pebbles etc. the Midgate drain should be flushed with water. First remove the drain grate:

  1. Lower the Midgate®. See Midgate® for more information.

  2. Object Number: 805436  Size: B3
  3. Pull up on the rear side of the drain grate, tilt it toward the front of the vehicle, and pull it out.

Reverse the procedure to reinstall the drain grate.

Cargo Area Floor Drains


Object Number: 805554  Size: B3

The cargo net has cut outs for the four cargo-area floor drains located under the cargo mat near the sides of the cargo area.

Periodically flush the drains through the cut outs to clear debris and allow water to drain from the cargo area. If the cargo area is extremely dirty lift up the edges of the cargo floor mat or take the whole mat out and flush the drains with water.