Chevrolet Silverado / GMC Sierra. Service manual — part 2434

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for IPC replacement, setup, and programming

OUTSIDE AIR TEMPERATURE DISPLAY INACCURATE OR 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.

Circuit/System Description

The inside rearview mirror (ISRVM) applies 5 volts to the ambient air temperature sensor. The
ambient air temperature sensor is a thermistor which varies in resistance as the temperature
changes. As the resistance of the ambient air temperature sensor increases, the ISRVM senses a
larger voltage drop across the sensor, indicating a lower temperature. As the resistance of the
ambient air temperature sensor decreases, the ISRVM senses a smaller voltage drop across the
sensor, indicating a higher temperature.

Diagnostic Aids

The following table will be used to measure the resistance of the sensor and compare it with the
actual ambient temperature. The mirror's temperature accuracy should be within 5 degrees of the
actual temperature. The actual temperature should not be taken from a radio station, a sign
displaying the temperature, etc. A temperature measuring tool such as a thermometer should be
used. Some temperature measuring tools may be within 5 degrees of the actual temperature. Make
sure to consult the manufacturer for the accuracy of the tool. This comparison can make the
mirror seem off by 5-10 degrees of the actual temperature when it is not.

Ambient Air Temperature Sensor Resistance

°C

°F

Minimum Resistance

K Ohms

Maximum
Resistance

K Ohms

-35

-31

234.81

250.59

-30

-22

171.69

182.31

-25

-13

126.82

133.99

-20

-4

94.63

99.49

-15

5

71.30

74.58

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Displays and Gages - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

Reference Information

Schematic Reference

Inside Rearview Mirror Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Instrument Cluster Description and Operation

Automatic Day-Night Mirror Description and Operation

Electrical Information Reference

Circuit Testing

Connector Repairs

Testing for Intermittent Conditions and Poor Connections

Wiring Repairs

-10

14

54.21

56.43

-5

23

41.48

43.17

0

32

32.00

33.31

5

41

24.96

25.83

10

50

19.61

20.19

15

59

15.49

15.94

20

68

12.31

12.67

25

77

9.85

10.12

30

86

7.96

8.15

35

95

6.45

6.61

40

104

5.27

5.39

45

113

4.32

4.42

50

122

3.56

3.64

55

131

2.95

3.02

60

140

2.46

2.52

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Displays and Gages - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Testing

1. Ignition OFF, disconnect the ambient air temperature sensor.

2. Ignition OFF, test for less than 1 ohm between the low reference circuit terminal B and

ground.

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

3. Ignition ON, verify that OC is displayed on the ISRVM display.

If not the specified value, test the signal circuit for a short to ground. If the circuit tests
normal replace the ISRVM.

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

ground. Verify that SC is displayed on the ISRVM display.

If not the specified value, test the signal circuit for an open/high resistance. If the
circuit tests normal replace the ISRVM.

5. If all circuits test normal, replace the ambient air temperature sensor.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ISRVM replacement, setup, and programming

SPEEDOMETER AND/OR ODOMETER INACCURATE OR 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.

Circuit/System Description

The instrument panel cluster (IPC) displays the vehicle speed based on the information from the
engine control module (ECM). The ECM converts the data from the vehicle speed sensor to a
4000 pulses/mile signal. The ECM sends the vehicle speed information via high speed GMLAN
serial data circuit to the body control module (BCM). The BCM then sends the information via

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Displays and Gages - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

low speed GMLAN to the IPC to order to display the vehicle speed and miles traveled.

Diagnostic Aids

Check for the following DTCs:

DTC B1000

DTC U2100

DTC U2105-U2199

Reference Information

Schematic Reference

Instrument Cluster Schematics

Connector End View Reference

Component Connector End Views

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, perform the speedometer gage sweep test with the scan tool. Verify that the

speedometer gage sweeps from its low to high position.

If the speedometer gage does not sweep from its low to high position, replace the IPC.

2. Ignition OFF, raise the vehicles drive wheels.

3. Engine ON, transmission in drive, verify the scan tool Vehicle Speed Sensor parameter

matches the speedometer display.

If the Vehicle Speed Sensor parameter does not match the speedometer display,

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Displays and Gages - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado