Chevrolet Silverado / GMC Sierra. Manual

Circuit/System Description

The windshield washer solvent heater operates with the standard windshield wiper washer
system, and when a heated washer cycle is activated the solvent heater controls the windshield
washers through the washer switch signal circuit to the body control module (BCM). The heater
is supplied with high current power and ground circuits that are used to energize the heater coils.
The low current logic voltage is supplied to the heater through the RUN relay in the underhood
fuse block. The RUN relay is a PCB relay energized by the BCM only while the engine is
running. The heated washer cycle operation is activated by a separate switch located on the
instrument panel accessory switch assembly. When the heated washer fluid switch is pressed the
heated washer switch signal circuit is momentarily grounded and the heated washer cycle is
activated. During the heated wash cycle the 3 heater elements in the solvent heater are energized,
and when the solvent temperature reaches approximately 70°C (160°F) the heater grounds the
washer switch signal circuit until the heated solvent is dispensed. The heated washer cycle will
run 4 heat and wash actions unless deacitvated by the heated washer switch signal.

Reference Information

Schematic Reference

Wiper/Washer Schematics

Connector End View Reference

Component Connector End Views

Switch Signal
Windshield Washer Switch
Signal

Washer Fluid Heated Control
Switch LED Control

Washer Solvent Heater
Assembly Ground

Washer Solvent Heater
Assembly Logic Ground

1. Windshield Washer Solvent Heater Malfunction
2. Windshield Washer Solvent Heater Indicator Inoperative
3. Windshield Washer Solvent Heater Indicator Always ON
4. Windshield Wiper System Malfunction

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Wipers and Washers - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

Description and Operation

Wiper/Washer System Description and Operation

Electrical Information Reference

Circuit Testing

Connector Repairs

Testing for Intermittent Conditions and Poor Connections

Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

1. Ignition ON, verify the washers operate using the washer switch.

If the base washer system does not operate, refer to Washer Malfunction.

2. Depress the heated washer switch. The heater washer fluid system should begin to cycle and

the driver information center (DIC) should displays the heated washer fluid pending
message.

If the heated washer fluid system does not begin to cycle, refer to Windshield Washer
Solvent Heater Malfunction below.

If the DIC does not display the heated washer fluid pending message, refer to Heated
Washer Fluid Indicator Malfunction below.

Circuit/System Testing

Windshield Washer Solvent Heater Malfunction

1. Ignition OFF, disconnect the X1 harness connector at the windshield washer solvent heater.

2. Test for less than 5 ohms between the ground circuit terminal 2 and ground.

If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 1 and

ground.

If the test lamp does not illuminate, test the B+ voltage circuit for an open/high
resistance. If the circuit fuse is open, test the B+ circuit for a short to ground. If the
circuit test normal, replace the windshield washer solvent heater.

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Wipers and Washers - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

4. Ignition OFF, connect the X1 harness connector at the windshield washer solvent heater.

Disconnect the X2 harness connector at the windshield washer solvent heater.

5. Test for less than 5 ohms between the ground circuit terminal 4 and ground.

If greater than the specified range, test the ground circuit for an open/high resistance.

6. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 6 and

ground.

If the test lamp does not illuminate, test the ignition circuit for a short to ground or an
open/high resistance. If the circuit tests normal, refer to Power Mode Mismatch .

7. Verify the scan tool Windshield Washer Switch parameter displays Inactive.

If not the specified value, test the signal circuit terminal 5 for a short to ground. If the
circuit tests normal, refer to Washer Malfunction.

8. Install a 3A fused jumper wire between the signal circuit terminal 5 and ground. Verify the

scan tool Windshield Washer Switch parameter displays Active.

If not the specified value, test the signal circuit for a short to voltage or an open/high
resistance. If the circuit tests normal, refer to Washer Malfunction.

9. Ignition OFF, connect a test lamp between the signal circuit terminal 1 and B+.

10. Command the heated washer system ON and OFF using the heated washer switch. The test

lamp should turn ON and OFF when changing between the commanded states.

If the test lamp is always ON, test the signal circuit for a short to ground. If the circuit
tests normal, test or replace the headlamp switch.

If the test lamp is always OFF, test the signal circuit for a short to voltage or and
open/high resistance. If the circuit tests normal, test or replace the headlamp switch.

11. If all circuits test normal, test or replace the windshield washer solvent heater.

Heated Washer Fluid Indicator Malfunction

1. Ignition OFF, disconnect the X2 harness connector at the windshield washer solvent heater.

2. Verify the heated washer fluid pending message is not displayed on the DIC.

If the message is displayed, test the signal circuit terminal 2 for a short to ground. If
the circuit tests normal, replace the IPC.

3. Ignition ON, install a 3A fused jumper wire between the signal circuit terminal 2 and

ground. Verify the heated washer fluid pending message is displayed on the DIC.

If the message is not displayed, test the signal circuit for a short to voltage or an
open/high resistance. If the circuit tests normal, replace the IPC.

4. If all circuits test normal, test or replace the windshield washer solvent heater.

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Wipers and Washers - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

Component Testing

Heated Washer Fluid Switch

1. Ignition OFF, disconnect the harness connector at the instrument panel accessory switch

assembly.

2. Test for infinite resistance between the switch signal circuit terminal 7 and the ground

circuit terminal 3 with the switch in the open position.

If less than infinite, replace the accessory switch assembly.

3. Test for less than 3 ohms between the switch signal circuit terminal 7 and the ground circuit

terminal 3 with the switch in the closed position.

If greater than 3 ohms, replace the accessory switch assembly.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Accessory Switch Replacement (with RPO SLT) or Accessory Switch Replacement
(without RPO SLT)

Windshield Washer Solvent Heater Replacement

MOISTURE SENSING FEATURE INOPERATIVE

Diagnostic Instructions

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

Review Strategy Based Diagnosis for an overview of the diagnostic approach.

Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Fault Information

Circuit

Short to

Ground

Open/High

Resistance

Short to

Voltage

Signal

Performance

Ignition Voltage

Outside Moisture Sensor
Signal 1

Outside Moisture Sensor
Signal 2

Ground

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Wipers and Washers - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

Content .. 3008 3009 3010 3011 ..

Chevrolet Silverado / GMC Sierra. Manual - part 3010