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Chevrolet Silverado / GMC Sierra. Manual - part 2795
Conditions for Running the DTC
The ignition is ON.
The system voltage is in the range of 9.5 - 17 volts.
The 5 volt supply for the SSR output auxiliary supply circuit is not faulted, and DTC C0870
is not set as current DTC.
The SSR relay control circuit fault DTC C1114 is not set as current DTC.
This DTC runs once per ignition cycle within the enabling conditions.
Conditions for Setting the DTC
DTC C1112 will set as current DTC, if one of the following conditions is true:
The TBCM detects an open in the relay control active low circuit.
The TBCM detects short to ground in the relay control active low circuit.
The TBCM detects short to battery positive in the relay control active low circuit.
The TBCM detects a open power circuit from fuse 65 or 61.
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).
Condition for Clearing the MIL/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 is an aftermarket trailer brake controller, the ITBC must be disconnected. Do not power
both ITBC and aftermarket controllers to control the trailer brakes at the same time.
Reference Information
Schematic Reference
Trailer Brake Control Schematics
2008 Chevrolet Silverado 1500
2008 BRAKES Trailer Brake Controls - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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 Verification
1. Ignition ON, observe the scan tool brake controls Trailer Brake Relay Status parameter.
The reading should be Enabled or Disabled.
2. Ignition ON, observe the scan tool brake controls TBCM Command Duty Cycle parameter.
The reading should be 0 - 100 percent.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the solid state relay.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal F and
ground.
If the test lamp does not illuminate, test the B+ circuit for a short to ground or an
open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test or
replace the trailer brake controller solid state relay.
3. Ignition ON, test for 4.8 - 5.2 volts between the 5-volt reference circuit terminal E and
ground.
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
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.
4. Ignition ON, test for 4.8 - 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.
5. If all circuits test normal, replace the trailer brake solid state relay.
Repair Procedures
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Trailer Brake Control Module Replacement
Control Module References for TBCM replacement, setup, and programming
DTC C1113
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 C1113 01
Trailer Brake Control Relay High Control Circuit Short to Battery
Diagnostic Fault Information
Circuit
Short to
Ground
High
Resistance
Open
Short to
Voltage
Signal
Performance
SSR Relay Control Circuit
C1113 01
-
C1113 01 C1113 01
-
Trailer Auxiliary Supply
-
-
-
C1113 01
-
2008 Chevrolet Silverado 1500
2008 BRAKES Trailer Brake Controls - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
Circuit/System Description
The trailer brake relay control circuit high SSR enable circuit short to battery monitors for short-
to-high faults on the trailer brake solid state relay (SSR) enable circuit. In general, the SSR
enable short-to-high circuit diagnostic is executed whenever the SSR has been disabled for a
minimum duration. Typically, the diagnosis is executed at TBCM power up. The diagnosis test
passes, if TBCM detected the status is correct for consecutive 16 samples.
Conditions for Running the DTC
The ignition is ON.
This DTC runs once per ignition cycle within the enabling conditions.
Conditions for Setting the DTC
The TBCM detects short to battery positive in the solid state relay control circuit.
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).
Condition for Clearing the MIL/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,
diagnose them first before to resolve DTCs described in this section.
If DTC C1114 is set as a current DTC, diagnose first before diagnosing DTC C1113. If there is
an aftermarket trailer brake controller, the ITBC must be disconnected. Do not power both ITBC
and aftermarket controllers to control the trailer brakes at the same time.
Reference Information
Voltage Circuit
2008 Chevrolet Silverado 1500
2008 BRAKES Trailer Brake Controls - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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