System Check Chart C-1

You have been directed here due to the climate control panel not entering diagnostics.

NOTE: The following step numbers refer to circled numbers on diagnostic chart. See Fig 1 . For climate control circuit identification, see Fig 2 .

This checks for operation of the "OFF" (and other) climate control buttons.
This checks for operation of the "Warmer" (red) button.
If both the "Off" and "Warmer" buttons work one at a time and diagnostics is still not entered, replace the Combo Panel.
For the Combo Panel to respond to key board buttons, it must "know" that the key is in run. This step checks for ISO-I3.
This step checks for good data to the Combo Panel on circuit 800B. If the ALDL pin and Combo Panel pin show the same voltage trend, then the circuit appears good.

Fig 1: Identifying System Check Chart C-1: Vehicle Will Not Enter Diagnostics Flow Chart

Courtesy of GENERAL MOTORS CORP.

Fig 2: Identifying System Check Chart A: Cluster Display Problem Flow Chart Circuit

Courtesy of GENERAL MOTORS CORP.