Hummer H1 Service Manual page 267

5-68 Transmission/Transfer Case
Diagnostic Aids
• Inspect the wiring for poor electrical connections at the
PCM and brake switch. Look for damaged terminals,
check for weak terminal tension, inspect for broken
wire.
• When diagnosing for a possible intermittent short or
open condition, move or massage the wiring harness
while observing test equipment for a change.
• Check customer driving habits and/or unusual driving
conditions (i.e. stop and go, expressway).
• Check brake switch for proper mounting and adjustment.
• Check for most current calibration I.D. and/or latest bul-
letins.
• If any engine DTCs or TPS codes are present diagnose
and clear these first. Then check to see if the transmis-
sion DTCs have reset.
Step
1 1. Connect scan tool.
2. Turn the ignition switch "on."
3. Record "Freeze Frame" and "Failure Records.'
4. Select "Brake Switch" on scan tool.
5. Disconnect brake switch connector from brake
switch.
6. Install a fused jumper from terminal "C" to terminal
"D" of brake switch connector.
Did brake switch status change from "Open" to
"Closed?'
2 Remove and inspect brake fuse for an open.
Was the fuse open?
3 Inspect switch wires for a short to ground.
Was a problem found and corrected?
4
Replace the brake switch.
5 Inspect switch-to-PCM circuit for open.
Is the repair complete?
6 Replace PCM.
7 1. After repair is complete, use scan tool to select
"DTC," then "Clear Info" function.
2. Select "Specific DTC" and enter DTC "P0719."
3. Ensure the following conditions are met:
• Engine running. Select Brake Switch" on scan
tool. Depress the brake to ensure the states
change with the pedal at rest and depressed.
Has the last test failed?
3-1-01
_____________________________________________
DTC P0719 Brake Switch Circuit - Low Input
Action Value Yes
—
Go to Step 5
—
Go to Step 4
—
Go to Step 8
—
Go to Step 8
—
Go to Step 8
—
Go to Step 8
—
Begin diagno-
sis again, Go to
Step 1
®
No
Go to Step 3
Go to Step 6
—
—
Go to Step 7
—
Repair veri-
fied, exit DTC
table.