Chevrolet Silverado / GMC Sierra. Service manual — part 2793
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 Testing
1. Ignition OFF, disconnect the harness connector of the TBCM.
2. Ignition ON, test for 11 volts or greater between the IGN 1 voltage circuit terminal 15 and
ground.
If less than the specified voltage, test the IGN 1 voltage circuit for a short to ground or
an open/high resistance. If the circuit test normal and the MISC - IGN fuse 44 is open,
test the voltage circuit for a short to ground. If the circuit tests normal, test or replace
the RUN/CRANK relay.
3. If all circuits test normal, and the DTC resets as current, replace the TBCM.
Repair Procedures
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for TBCM replacement, setup, and programming
DTC C0870
Diagnostic Instructions
IMPORTANT: Verify that stop lamp DTCs are not set as current or history
before performing this diagnostic. If stop lamp DTCs are set as
current or history, go to lighting for diagnose.
2008 Chevrolet Silverado 1500
2008 BRAKES Trailer Brake Controls - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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 C0870
Device Voltage Reference Output 1 Circuit
Circuit/System Description
The TBCM runs this diagnostics to check whether there is a fault on the internal TBCM 5 volt
references used to monitor the SSR Control and Trailer Feedback circuits. This diagnostics
checks if the circuits' 5 volt references is within a range for normal operation.
Conditions for Running the DTC
The system voltage is in the range of 9.5 volts.
The module initialization has taken place.
Conditions for Setting the DTC
The TBCM circuit reference voltage for the SSR is below 4.8 volts or above 5.2 volts.
Action Taken When the DTC Sets
The trailer brake control will be disabled for the remainder of the ignition cycle.
The Service Trailer Brake System will be displayed on the Driver Information Center
(DIC).
Conditions for Clearing the DTC
When the condition for the DTC is no longer present.
The TBCM automatically clears the history DTC when a current DTC is not detected in 40
consecutive drive cycles.
Diagnostic Aids
If there are any DTCs set for GMLAN communication such as U0100, U0121, U0140, or U2099
or the antilock brake control system, diagnose them first before to resolve DTCs described in this
section.
2008 Chevrolet Silverado 1500
2008 BRAKES Trailer Brake Controls - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
Reference Information
Schematic Reference
Trailer Brake Control Schematics
Description and Operation
Trailer Brake Controls Description and Operation
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 Testing
1. Ignition OFF, disconnect the harness connector at the solid state relay module.
2. Test for less than 5 ohms of resistance between the ground circuit terminal B and ground.
If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, test for 4.85 - 5.2 volts between the 5-volt reference circuit terminal C and
ground.
If less than the specified range, test the 5-volt reference circuit for a short to ground or
an open/high resistance. If the circuit tests normal, replace the TBCM.
If greater than the specified range, test the 5-volt reference circuit for a short to
voltage. If the circuit tests normal, replace the TBCM.
IMPORTANT: All electrical components and accessories must be turned OFF
and allowed to power down.
2008 Chevrolet Silverado 1500
2008 BRAKES Trailer Brake Controls - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
4. If all circuits test normal, replace the trailer brake solid state relay.
Repair Procedures
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for TBCM replacement, setup, and programming
DTC C0880
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 C0880
Device Voltage Reference Output 2 Circuit
Diagnostic Fault Information
Circuit/System Description
The TBCM runs this diagnostics to check whether there is a fault on the internal TBCM 5 volt
references used to monitor the User Gain switch circuits. This diagnostics checks if the circuits' 5
volt references is within a range for normal operation.
Conditions for Running the DTC
The system voltage is in the range of 9.5 - 17 volts.
The module initialization has taken place.
Conditions for Setting the DTC
Circuit
Short to
Ground
High
Resistance
Open
Short to
Voltage
Signal
Performance
Device Voltage Reference
Output 2 Circuit
C0880
-
-
C0880
-
2008 Chevrolet Silverado 1500
2008 BRAKES Trailer Brake Controls - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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