MODEL IDENTIFICATION
| Series (1) | Model |
|---|---|
| A | FWD Aztek |
| B | AWD Aztek |
| C | 2WD Pickup, Tahoe & Yukon |
| K | 4WD Escalade, Pickup, Tahoe & Yukon |
| U | Silhouette, Trans Sport & Venture |
| (1) Vehicle series code is fifth character of VIN. | |
| (1) | Vehicle series code is fifth character of VIN. |
MODEL IDENTIFICATION (LIGHT TRUCKS & VANS)
All FWD and some RWD vehicles use an electric cooling fan. The electric cooling fan is used for radiator and A/C condenser cooling. Cooling fan operates when A/C is on and when engine coolant temperature exceeds a specific value. One or more cooling fan relays may be used. See COOLING FAN RELAY LOCATION table. Some RWD trucks, vans and motorhomes are equipped with an auxiliary electric cooling fan. See WIRING DIAGRAMS .
| Application | Location |
|---|---|
| "A" & "B" Series | In Underhood Fuse Block, Above Battery |
| "C" & "K" Series | On Engine Compartment Fuse/Relay Block Near Anti-Lock Brake Control Module |
| "U" Series | Inside Electrical Center At Right Front Of Engine Compartment |
COOLING FAN RELAY LOCATION
Description
Engine cooling fan system consists of two electrical cooling fans and three fan relays. Relays are arranged in a series/parallel configuration that allows Powertrain Control Module (PCM) to operate both fans together at low or high speeds. Cooling fans and fan relays receive battery voltage from underhood accessory wiring junction block.
During low speed operation, PCM supplies ground path for low speed fan relay through low speed cooling fan relay control circuit. This energizes cooling fan 1 relay coil, closes relay contacts, and supplies battery voltage from cool fan 1 fuse through cooling fan motor supply voltage circuit to left cooling fan. Ground path for left cooling fan is through cooling fan 2 relay and right cooling fan. Result is a series circuit with both fans running at low speed.
During high speed operation, PCM supplies ground path for cooling fan 1 relay through low speed cooling fan relay control circuit. After a 3-second delay, PCM supplies a ground path for cooling fan 3 relay and cooling fan 2 relay through high speed cooling fan relay control circuit. This energizes cooling fan 2 relay coil, closes relay contacts, and provides a ground path the left cooling fan. At the same time, cooling fan 2 relay coil is energized closing relay contacts and provides battery voltage from cool fan 2 fuse on cooling fan motor supply voltage circuit to right cooling fan. During high speed fan operation, both engine cooling fans have there own ground path. Result is a parallel circuit with both fans running at high speed.
PCM commands low speed fans on under the following conditions
- Engine coolant temperature exceeds about 223°F (106°C).
- A/C refrigerant pressure exceeds 190 psi (13 Kg/cm 2 ).
- After vehicle is shut off, if engine coolant temperature at key-off is greater than 284°F (140°C) and system voltage is more than 12 volts. Fans will stay on for approximately 3 minutes.
PCM commands high speed fans on under the following conditions
- Engine coolant temperature reaches 230°F (110°C).
- A/C refrigerant pressure exceeds 240 psi (17 Kg/cm 2 ).
- When certain DTCs set.
Engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. Relays are arranged in a series/parallel configuration that allows Powertrain Control Module (PCM) to operate both fans together at low or high speeds. Cooling fans and fan relays receive battery voltage from underhood junction block.
During low speed operation, PCM supplies ground path for low speed fan relay through low speed cooling fan relay control circuit. This energizes cooling fan 1 relay coil, closes relay contacts, and supplies battery voltage from cool fan 1 maxifuse® through cooling fan motor supply voltage circuit to left cooling fan. Ground path for left cooling fan is through cooling fan relay and right cooling fan. Result is a series circuit with both fans running at low speed.
During high speed operation, PCM supplies ground path for cooling fan 1 relay through low speed cooling fan relay control circuit. After a 3-second delay, PCM supplies a ground path for cooling fan 2 relay and cooling fan relay through high speed cooling fan relay control circuit. This energizes cooling fan relay coil, closes relay contacts, and provides a ground path for left cooling fan. At the same time, cooling fan 2 relay coil is energized closing relay contacts and provides battery voltage from cool fan 2 maxifuse® on cooling fan motor supply voltage circuit to right cooling fan. During high speed fan operation, both engine cooling fans have there own ground path. Result is a parallel circuit with both fans running at high speed.
Auxiliary cooling fan is controlled by VCM based on inputs from the A/C system, engine coolant temperature sensor and vehicle speed sensor. Battery voltage is supplied to the auxiliary cooling fan relay. If ignition voltage is supplied to auxiliary fan relay (coil side). VCM controls cooling fan by relay by providing a ground path.
VCM will turn on auxiliary cooling fan when certain Diagnostic Trouble Codes (DTCs) are present, engine coolant temperature is more than 225°F (107°C) or A/C head pressure is more than 300 psi (21 Kg/cm 2 ). Auxiliary cooling fan will remain on for at least 30 seconds. VCM will turn auxiliary cooling fan off when engine coolant temperature has dropped 7°F (4°C) or A/C head pressure has dropped to 250 psi (18 Kg/cm 2 ).
Note. Check VCM DTCs that may affect system. If any DTCs are present, perform testing for applicable DTC. Some DTCs may cause auxiliary cooling fan to stay on at all times. Repair all DTCs that are set before proceeding with testing. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.