Switch-on Criteria for Activation of Auxiliary Air Heater Heating Element (Z35)

Switch-on Criteria for Activation of Auxiliary Air Heater Heating Element (Z35)

The Engine Control Module (ECM) actuates Auxiliary Air Heater Heating Element (Z35) via Preheating Coolant, Low Heat Output Relay (J359) and Preheating Coolant, High Heat Output Relay (J360) in the event the following requirements are met:

• There is a Ground (GND) signal at the ECM from Heater Control Module (J65).

• Engine is running for a minimum of 8 seconds and engine speed is greater than 500 RPM.

• Engine temperature is lower than 75 °C (167° F).

• The calculated outside air temperature is lower than 8 °C (46° F).

• Vehicle voltage supply is greater than 12.2 volts and no request that forbids the switch-on is sent by Vehicle Electrical System Control Module (J519).

• No DTC is stored in the ECM and Generator load is less than 30 to 77% (depending on engine speed)

• The ECM actuates both auxiliary heater relays for the auxiliary heater heating element so that the load on the Generator does not exceed 95%. Refer to Vehicle Diagnosis, Testing and Information System in the "Guided Fault Finding" function (for ECM) and. Thus the next stage is switched on only in the event Generator load is less than 30 to 77%, depending on engine speed.