Diagnostic Modes

ON-BOARD DIAGNOSTICS
Display Console
The Heater, Ventilation and Air Conditioning (HVAC) control is used to display both Diagnostic Trouble Codes (DTCs) and data parameters for many of the vehicles' control modules.

Control Modules
Control modules that display information through the HVAC include the Engine Control Module (ECM) DTCs, Supplemental Inflatable Restraint (SIR) DTCs, Antilock Brake System/Traction Control (ABS/TC) DTCs, HVAC Automatic Control Air Conditioning (ACAC) DTCs and Central Control Module (CCM) DTCs.

DIAGNOSTIC DISPLAY TYPES
There are two types of displays available after entering the diagnostic mode.

Diagnostic System Pointers
A diagnostic pointer (a minus sign followed by a two digit number) indicates what system is being displayed.

Pointer Pointer Description
-00 ECM System DTCs
-01 CCM System DTCs
-02 ACAC System (HVAC) DTCs
-03 SIR System DTCs
-04 ABS/TC System DTCs

Inputs/Outputs
The second display type available is the ACAC input/output. This display displays which parameter you are observing including the actual Diagnostic Trouble Code that you are viewing for pointer selection -00 through -04.

Diagnostic System Parameters

Pointer Parameter Description Display Range
-05 Program Number 0 - 255 Counts
-06 Engine RPM Display in 100's
-12 Vehicle Speed In MPH
-16 Sun Load Sensor 200+ = dark, 150- = light
-17 Current Temperature Valve Position 0 - 255 Counts
-19 Temperature Valve Position (Hot) 180 - 255 Counts
-20 Temperature Valve Position (Cold) 5 - 60 Counts
-21 Engine Coolant Temperature °C
-25 In Vehicle Sensor -
-28 Ambient Sensor Counts
-30 Ignition Cycles (HVAC) 0 - 199


DTC DISPLAY ORDER
Current DTCs
If any current DTCs exist, they will be shown cycling sequentially, 1.6 seconds at a time. DTCs will be continually displayed in the HVAC control display starting with the lowest current DTC through the highest current DTC.

History DTCs
After displaying current DTCs, history DTCs will display starting with the lowest DTC through the highest history DTC. Current DTCs will then repeat followed by history DTCs. This will continue until diagnostics are exited or the ignition is shut "OFF."

LOSS OF SERIAL DATA
Whenever the HVAC control display shows "--" this indicates the HVAC control is not receiving serial data because of a fault on the serial data line to and including the HVAC control.