Service Procedure
Figure 1:
SERVICE PROCEDURE
INSPECTION:
Raise truck on hoist and check white 4-way connector at front axle for wire colors (Figure 1, page 5). If wire in cavity "A" is brown, the truck has the correct wiring harness. If correct, lower truck and proceed to step 21.
If wire in cavity "A" is blue, harness and front axle switch must be changed. Lower truck and proceed to "Repair" section below.
REPAIR:
1. Prepare truck; disconnect negative battery cable.
2. Remove clamp on right frame rail which holds battery cable and wiring conduit for the front axle switch.
3. For vehicles with dual rear wheels (RPO R05) only, disconnect relay connector from inside convenience center at right side of truck. Relay connector will be the one toward the driver's side (Figure 1, page 5).
Figure 2:
4. Disconnect engine wiring harness connector behind the engine (Figure 2, View A, page 6). This is a purple wire behind the engine located approximately at the edge of the transmission bell housing. This connector is more accessible from under the hood, but it is viewed easier from under the truck. Thus you may want to raise the truck before disconnecting this connector.
5. Raise truck on hoist.
6. Disconnect white 4-way connector from front axle engagement switch, and disconnect the connector to the actuator (located directly next to the white 4-way connector).
7. Open harness clip which is bolted to transmission bell housing just above starter heat shield (Figure 2, View A), and open harness clip located on top right of transfer case (Figure 2, Main View, page 6).
8. Disconnect the following three connectors on left side of transmission (Figure 2, Main View, page 6). One connects to the indicator lamp (attached to the floor pan), one to the front side of the transfer case, and one to the output speed sensor (a brass colored piece on the side of the transmission).
For trucks with MT1 (4L80E) transmissions, there will be an additional two pin connector extension from the output speed sensor which should be disconnected.
9. Disconnect harness from back of transfer case at vehicle speed sensor (Figure 2, View B, page 6). For trucks with dual rear wheels (RPO R05) there is an additional connector with a large red wire to be disconnected.
10. Fabricate a pull wire about four (4) to five (5) feet long, and attach it to front axle end of harness.
11. Pull harness through the starter heat shield from transmission side of truck, leaving pull wire running through the heat shield.
12. Connect new harness to pull wire on front axle connector side of harness and tape over the two connectors to allow them to pass through the heat shield easily.
13. Pull new harness through heat shield toward the front axle side.
14. Remove and replace front axle engagement switch.
15. Reconnect harness to front axle engagement switch and actuator, and tie strap the harness to the starter wires at the bottom of the starter heat shield.
Figure 1:
NOTICE: Harness must be looped under battery cable harness on frame rail to prevent harness from touching the exhaust manifold (Figure 1).
16. Connect the connectors to left side of transmission and rear of transfer case. Reclip harness to clip at top right of the transfer case and to the clip bolted onto transmission bell housing.
17. For trucks with dual rear wheels (RPO R05), attach pull wire to relay connector, and feed pull wire up through truck to assist in retrieving this connector.
18. Lower truck, and reconnect engine wiring harness connector (purple wire) and relay connector (if equipped with dual rear wheels - RPO R05) located in the convenience center.
19. Refasten clamp on right frame rail, keeping harness routed under battery cable and free from exhaust manifold.
20. Reconnect battery and road test truck to verify proper operation of 4wd indicator lamp.
21. Install Campaign Identification Label.