Service Brake System

finleereal · June 4, 2008

I have a 2007 GMC Sierra Classic, 4.8L, Auto Trans. I changed the rear gears from 3.23 to 3.73. I have an error message Service Brake System, along with 36 beeps. I recalibrated the speedometer and still have the error message. DTCs are P0449 and C0245. Please help me fix the problem.

jrrod2004 · June 4, 2008

Service Information

2007 GMC Truck Sierra - 2WD | Sierra, Silverado (VIN C/K) Service Manual | Document ID: 1857085 DTC P0443 or P0449

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 Descriptors

DTC P0443: Evaporative Emission (EVAP) Purge Solenoid Control Circuit

DTC P0449: Evaporative Emission (EVAP) Vent Solenoid Control Circuit

Diagnostic Fault Information

Circuit

Short to Ground

High Resistance

Open

Short to Voltage

Ignition 1 Voltage - Purge Supply

P0443

--

Battery Positive - Vent Supply

P0449

--

EVAP Purge Solenoid Control

P0443

EVAP Vent Solenoid Control

P0449

Circuit/System Description

P0443

An ignition voltage is supplied directly to the normally closed evaporative emission (EVAP) canister purge solenoid valve. The EVAP canister purge solenoid valve is pulse width modulated (PWM). The scan tool displays the amount of ON time as a percentage. The control module monitors the status of the driver. The control module controls the EVAP canister purge solenoid valve ON time by grounding the control circuit via an internal switch called a driver.

P0449

Battery voltage is supplied to the EVAP canister vent solenoid valve. The control module grounds the EVAP canister vent solenoid valve control circuit to close the valve by means of an internal switch called a driver. The scan tool displays the commanded state of the EVAP canister vent solenoid valve as ON or OFF. The control module monitors the status of the driver.

Conditions for Running the DTC

• The ignition is ON.

• The system voltage is between 9-18 volts.

• DTCs P0443 and P0449 run continuously when the above conditions are met.

Conditions for Setting the DTC

The control module detects that the commanded state of the driver and the actual state of the control circuit do not match for a minimum of 5 seconds.

Action Taken When the DTC Sets

DTCs P0443 and P0449 are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTCs P0443 and P0449 are Type B DTCs.

Reference Information

Schematic Reference

Engine Controls Schematics

Description and Operation

Evaporative Emission Control System Description

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Connector End View Reference

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Engine Control Module Connector End Views

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Engine Controls Connector End Views

Electrical Information Reference

•

Circuit Testing

•

Troubleshooting with a Test Lamp

•

Testing for Intermittent Conditions and Poor Connections

•

Wiring Repairs

Scan Tool Reference

•

Scan Tool Data List

•

Scan Tool Output Controls

Circuit/System Verification

P0443

With the ignition ON, engine OFF, you should hear a clicking sound when the EVAP canister purge solenoid valve is commanded to 50 percent with a scan tool. The clicking sound should stop when the EVAP canister purge solenoid valve is commanded to 0 percent. The rate at which the valve cycles should increase when the commanded state is increased, and decrease when the commanded state is decreased.

P0449

With the ignition ON and the engine OFF, command the EVAP vent solenoid ON and OFF with a scan tool.
Listen for a click when the valve operates. Verify that both the ON and the OFF states are commanded.

Circuit/System Testing

P0443

Ignition OFF, disconnect the harness connector at the EVAP canister purge solenoid valve.
Ignition ON, verify that a test lamp illuminates between the voltage supply circuit terminal A and ground.
?If the test lamp does not illuminate, test the voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and the voltage supply circuit fuse is open, test or replace the EVAP canister purge solenoid.
Connect a test lamp between the voltage supply circuit terminal A and the control circuit terminal B.
Command the solenoid to 50 percent with a scan tool. The test lamp should flash or illuminate when commanded to 50 percent and turn OFF when commanded to 0 percent.
?If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the control module.

?If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the control module.
If all circuits test normal, replace the EVAP canister purge solenoid valve.

P0449

Ignition OFF, disconnect the harness connector at the EVAP canister vent solenoid valve.
Ignition ON, verify that a test lamp illuminates between the voltage supply circuit terminal A and ground.
?If the test lamp does not illuminate, test the voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and the voltage supply circuit fuse is open, test or replace the EVAP canister vent solenoid.
Connect a test lamp between the voltage supply circuit terminal A and the control circuit terminal B.
Command the solenoid ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between states.
?If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the control module.

?If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the control module.
If all circuits test normal, replace the EVAP canister vent solenoid valve.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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Evaporative Emission Canister Vent Solenoid Valve Replacement

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Control Module References for ECM replacement, setup, and programming

jrrod2004 · June 4, 2008

Service Information

2007 GMC Truck Sierra - 2WD | Sierra, Silverado (VIN C/K) Service Manual | Document ID: 1852855 DTC C0245

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 C0245 00: Wheel Speed Sensor Frequency Error

DTC C0078 00: Wheel Speed Sensor Frequency Error (PHT)

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Wheel Speed Sensor Frequency Error

--

C0245 00

C0078

Circuit/System Description

The wheel speed sensor receives a 12-volt power supply voltage for vehicles equal to or under 8600 GVW or 5-volt for vehicles over 8600 GVW from the electronic brake control module (EBCM) and provides an output signal to the EBCM. As the wheel spins, the wheel speed sensor sends the EBCM a DC square wave signal. The EBCM uses the frequency of the square wave signal to calculate the wheel speed.

Conditions for Running the DTC

• The ignition is ON.

• Ignition voltage is greater than 9.5 volts.

• No wheel speed sensor faults exist.

• Brake is not applied.

• Vehicle is not cornering.

• No wheel spinning is detected.

Conditions for Setting the DTC

Wheel speed differences between one wheel and the others is greater than 25 percent.

Action Taken When the DTC Sets

• Antilock Brake System (ABS), Traction Control System (TCS) and Vehicle Stability Enhancement System (VSES) are disabled for the remainder of the ignition cycle.

• The ABS and Stabilitrak indicator turns ON.

• The service Traction Control and Stabilitrak displays on the DIC.

Conditions for Clearing the DTC

• The DTC becomes history when the conditions for setting the DTC are no longer present.

• The history DTC clears after 100 malfunction-free ignition cycles.

• The EBCM receives a clear code command from the scan tool.

Diagnostic Aids

• Faulty wheel speed sensor will not set this DTC.

• A vehicle using a space saver spare will not set this code.

Reference Information

Schematic Reference

Antilock Brake System Schematics

Connector End View Reference

Antilock Brake System Connector End Views

Description and Operation

ABS Description and Operation

Electrical Information Reference

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Circuit Testing

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Connector Repairs

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Testing for Intermittent Conditions and Poor Connections

•

Wiring Repairs

Scan Tool Reference

Scan Tool Data List for EBCM

Circuit/System Verification

Inspect for one tire that has improper air pressure or improper size.
Inspect the wheel speed sensors and tone rings for damage, incorrect application, or incorrect installation.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.