• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
• | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
• | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
---|---|---|---|---|
Coolant ByPass Valve Solenoid Control | 1 | 1 | -- | -- |
Coolant ByPass Valve Solenoid Ground | -- | 1 | 1 | -- |
1. Auxiliary Air Temperature Malfunction |
The purpose of the auxiliary heating system is to supply heat to the rear interior of the vehicle. The heater auxiliary blower motor switch is located on the headliner and controls the auxiliary blower motor speeds for rear heater operation. Placing the heater auxiliary blower motor switch in any position other than OFF, turns on the solenoid allowing vacuum to open the water valve, this action allows coolant to flow through the auxiliary heater core. The location of the hot water shut off valve is under the right rear area of the cab. The only way to regulate the temperature of the air is to regulate the blower speed.
Control Module References for scan tool information
Ignition ON, engine running, place the auxiliary blower switch in the LO, MED and HI speed positions. The auxiliary motor should activate and operate from low to medium to high when changing between the commanded states.
⇒ | If the blower motor speed does not change or fails to operate at a selected speed, refer to Auxiliary Blower Motor Malfunction . |
⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
⇒ | If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit test normal, test or replace the auxiliary HVAC control assembly. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.