Preliminary Information

This article contains only information required to test electric cooling fans. Other diagnostic information may be referenced while performing electric cooling fan diagnosis. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE for complete information on engine control systems.

Some truck models are equipped with an auxiliary electric cooling fan. The auxiliary electric cooling fan is not controlled by Powertrain Control Module (PCM).

Trouble shoot cooling fan using appropriate diagnostic information provided. For cooling fan relay location, see COOLING FAN RELAY LOCATION table.

To help save diagnostic time, always check for blown fuses or fusible links before proceeding with any testing. If fuses are blown, locate and repair short circuit before replacing fuses. Ensure all related relay and wire harness connections are clean and tight. Repair as necessary. See WIRING DIAGRAMS for component, terminal and wire color identification.

NOTE: Vehicles may be equipped with a PCM/VCM using an Electronically Erasable Programmable Read Only Memory (EEPROM). When replacing PCM/VCM, the new PCM/VCM must be programmed.