Early Fuel Evaporation ( EFE ): Testing and Inspection

Diagnostic Chart:

Early Fuel Evaporative (EFE) Heater Schematic:

Circuit Description:
The early fuel evaporation (EFE) heater provides a source of rapid heat to the air/fuel mixture during cold start conditions. Rapid heating provides quick fuel evaporation, a more uniform fuel distribution and also reduces the length of time the engine is in "open loop," reducing the exhaust emission levels. When the engine control module (ECM) determines that the engine coolant temperature is below operating temperature and the engine speed is above idle, it will energize the EFE heater relay coil. Voltage will then be applied to the EFE heater through the EFE heater relay contacts. When the engine reaches operating temperature, or the engine speed is reduced to idle, the ECM will de-energize the EFE system.

Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

1. This checks for an open in YEL/RED wire between EFE heater relay and ECM or for a faulty ECM.
2. This checks for an open in WHT/BLU wire between EFE heater relay and FI relay.
3. This checks for an open in WHT wire between EFE heater relay and fuse box II or for a faulty EFE heater relay.
4. This checks for a faulty WHT/BLK or BLK wire or for a faulty EFE heater.