Chevrolet Silverado / GMC Sierra. Manual — part 720

9. Reconnect the EBCM harness connector.

10. Ignition ON, test voltage of phase A phase B, and phase C. verify that the reading is battery

positive voltage for each of the three phases.

If not the specified value, test the phase A phase B, and phase C circuits for a short to
ground or an open/high resistance. If the circuit tests normal, replace the EBCM.

11. Ignition OFF, reconnect the SAS. Turn the ignition ON. Using the scan tool, rotate the

steering wheel and observe the SAS. Verify the sensor sweeps through the entire range
while monitoring the steering wheel as it rotates in degrees from the input signals between
circuit phase A and the signal circuit phase B. The rotation in degrees should vary between
phase A and phase B without any spikes or dropouts.

If not within the specified range or is erratic, replace the steering angle sensor.

12. If the sensor test normal, replace the EBCM.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Vehicle Yaw Sensor with Vehicle Lateral Accelerometer Replacement

Control Module References for EBCM replacement, setup, and programing

DTC C0774

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.

DTC Descriptor

DTC C0774 00

Low Tire Pressure System Performance

Circuit Description

The tire pressure monitor (TPM) system has 4 radio frequency (RF) transmitting pressure sensors
inside each wheel/tire assembly. If a sensor detects a low tire pressure, the DIC will display the
CHECK TIRE PRESSURE, and the Electronic Brake Control Module (EBCM) will receive a
serial data message that a DTC C0774 has set. The Vehicle Stability Enhancement System

2008 Chevrolet Silverado 1500

2008 BRAKES Antilock Brake System - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

(VSES) will compensate for the low tire pressure with a calibration change to low tire present.
Review the TPM for diagnostics for C0774.

Conditions for Running the DTC

Vehicle speed is 32 km/h (20 mph), or greater for 1 minute.

Conditions for Setting the DTC

The TPM detects a tire pressure difference in 1 tire of 8.2 kPa (1.2 psi) higher or lower than
the other 3.

The EBCM will receive a serial data message that a DTC C0774 has set.

Actions Taken When the DTC Sets

A DTC C0774 is stored in memory.

The VSES system compensates for low tire pressure.

Conditions for Clearing the DTC

A current DTC will clear when the TPM system is reset.

A history DTC will clear after 100 consecutive malfunction-free ignition cycles from when
the TPM system has been reset.

Diagnostic Aids

A possible cause of this DTC could be a low tire pressure in one of the four tires.

Scan Tool Reference

Control Module References for Scan Tool Information

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

DTC C1100 OR C1101

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.

2008 Chevrolet Silverado 1500

2008 BRAKES Antilock Brake System - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

DTC Descriptor

DTC C1100 00

Brake Booster Vacuum Sensor Performance

Diagnostic Fault Information

Circuit/System Description

The electronic brake control module (EBCM) provides a power 5-volt reference to the brake
booster vacuum sensor. The brake booster vacuum sensor converts the change in vacuum levels in
the brake booster into a voltage signal. This signal is sent to the EBCM. The voltage signal
ranges, from 0.13-3.30 volts depending on vacuum levels. The low reference is the return side of
the sensor to ground.

Conditions for Running the DTC

The ignition is ON.

Ignition voltage is greater than 9 volts.

Conditions for Setting the DTC

Voltage at the brake booster sensor signal output to the EBCM falls outside the 0.13-3.30
volts range for more than 200 milliseconds.

The power 5-volts reference is shorted to ground or battery positive.

Action Taken When the DTC Sets

One or more of the following actions may occur:

The red BRAKE Warning indicator turns ON.

Conditions for Clearing the DTC

Circuit

Short to

Ground

Open/High

Resistance

Short to

Voltage

Signal

Performance

Brake Booster Vacuum 5-Volt
Reference Circuit

C1100

C1100

C1100

-

Signal Circuit

C1100

C1100

C1100

-

Low Reference Circuit

-

C1100

-

-

2008 Chevrolet Silverado 1500

2008 BRAKES Antilock Brake System - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

The condition for the DTC is no longer present.

The EBCM automatically clears the history DTC when a current DTC is not detected in 100
consecutive drive cycles.

Reference Information

Schematic Reference

Antilock Brake System Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

ABS Description and Operation (With JL4) or ABS Description and Operation (Without
JL4)

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 Testing

1. Ignition OFF, disconnect the harness connector at the brake booster vacuum sensor.

2. Test for less than 3.0 ohm of resistance between the low reference circuit terminal A and

ground.

If greater than 3.0 ohm, test the low reference circuit for an open/high resistance. If the
circuit tests normal, replace the EBCM.

3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal B and

ground.

If less than 4.8 volts, test the 5-volt reference circuit for a short to ground or an

2008 Chevrolet Silverado 1500

2008 BRAKES Antilock Brake System - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado