Chevrolet Silverado / GMC Sierra. Service manual — part 1684

Fig. 277: View Of Coolant Heater Cord, Clip Retainer & Bolt
Courtesy of GENERAL MOTORS CORP.

1. Install the coolant heater cord to the vehicle.

2. Position the coolant heater cord clip to the frame and install the coolant heater cord bolt

(3).

Tighten: Tighten the bolt to 8 N.m (71 lb in).

3. Raise the vehicle.

4. Install the coolant heater cord clip retainer (2) to the frame.

NOTE:

Refer to Fastener Notice .

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Cooling - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

5. Install the coolant heater cord clip (1) to the front brake front pipes.

Fig. 278: View Of Coolant Heater Cord
Courtesy of GENERAL MOTORS CORP.

6. Connect the coolant heater cord electrical connector.

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Cooling - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

Fig. 279: View Of Oil Pan Skid Plate & Bolts
Courtesy of GENERAL MOTORS CORP.

7. Position the oil pan skid plate and install the 2 front bolts and tighten the 2 rear bolts, if

equipped.

Tighten: Tighten the bolts to 20 N.m (15 lb ft).

8. Lower the vehicle.

DESCRIPTION AND OPERATION

COOLING FAN DESCRIPTION AND OPERATION (W/O LFA)

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Cooling - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

Cooling Fan Control - Two Fan System

The engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. The relays are
arranged in a series/parallel configuration that allows the engine control module (ECM) to
operate both fans together at low or high speeds. The cooling fans receive positive voltage from
the cooling fan relays which receive battery positive voltage from the underhood fuse block. The
fan relay coils receive ignition 1 voltage from the powertrain relay.

During low speed operation, the ECM supplies the ground path for the low speed fan relay
through the low speed cooling fan relay control circuit. This energizes the low speed fan relay
coil, closes the relay contacts, and supplies battery positive voltage from the low fan fuse through
the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left
cooling fan is through the cooling fan series/parallel relay and the right cooling fan. The result is a
series circuit with both fans running at low speed.

During high speed operation the ECM supplies the ground path for the low speed fan relay
through the low speed cooling fan relay control circuit. The ECM grounds the high speed fan
relay and the cooling fan series/parallel relay through the high speed cooling fan relay control
circuit. This energizes the cooling fan control relay coil, closes the relay contacts, and provides a
ground path for the left cooling fan. At the same time the high speed fan relay coil is energized
closing the relay contacts and provides battery positive voltage from the high fan fuse on the
cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation,
both engine cooling fans have their own ground path. The result is a parallel circuit with both fans
running at high speed.

Refer to Engine Cooling Schematics.

COOLING SYSTEM DESCRIPTION AND OPERATION

Engine Coolant Indicators

ENGINE COOLANT HOT

The instrument panel cluster (IPC) displays ENGINE COOLANT HOT message when the IPC
receives a class 2 message from the powertrain control module (PCM) requesting illumination of
this driver warning.

ENGINE OVERHEATED

The IPC displays ENGINE OVERHEATED message when the IPC receives a class 2 message
from the PCM requesting illumination of this driver warning.

LOW COOLANT LEVEL B

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Cooling - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado