C2129-16
C2129-16 BATTERY VOLTAGE - CIRCUIT VOLTAGE BELOW THRESHOLD
Theory of Operation
The Integrated Trailer Brake Module (ITBM) communicates with the vehicle through the high speed CAN B bus. The ITBM monitors the Brake Pedal Status and Vehicle Speed. It also outputs the Trailer Status, Gain Setting, and Brake Output Power to the vehicle. The ITBM connects to the electric trailer brakes through the 7-Way connector and controls the brake force through a Pulse Width Modulating (PWM) duty cycle.
NOTE: If there is no trailer connected there will be NO Pulse Width Modulating (PWM) signal.
The ITBM controls the PWM output to the trailer brakes in two ways. The first occurs while the brake pedal becomes active, the PWM is proportional to the rate of deceleration measured by the accelerometer inside the ITBM. The second is the manual lever on the ITBM that can be controlled by the driver. If both are active, the greater of the two, in terms of PWM output, will prevail.
- When Monitored:
Ignition on.
- Set Condition:
If the sensed ignition voltage drops below 9.5 volts for 100 msec.
1. DTC IS ACTIVE
NOTE: Diagnose and repair any powertrain Charging system DTCs before continuing with this procedure.
NOTE: Make sure the battery is fully charged.
1. Ignition on, engine not running.
2. With the scan tool, record and erase DTCs.
3. Turn ignition off to the lock position.
4. Start the engine.
5. With the scan tool, read DTCs.
Is the status Active for this DTC?
Yes
- Go To 2
No
- Go To 6
2. (F943) IGNITION RUN/START CONTROL OUTPUT CIRCUIT OPEN OR HIGH RESISTANCE
1. Turn ignition off to the lock position.
2. Disconnect the ITBM C2 harness connector.
3. Check connectors - Clean/repair as necessary.
4. Ignition on, engine not running.
5. Using a 12-volt test light connected to ground, check the (F943) Ignition Run/Start Control Output circuit.
NOTE: Compare the brightness to that of a direct connection to the battery.
Does the test light illuminate brightly?
Yes
- Go To 3
No
- Repair the (F943) Ignition Run/Start Control Output circuit for a short to ground, an open circuit, or high resistance.
- Perform the ITBM VERIFICATION TEST. Integrated Trailer Brake Module (ITBM) Verification Test.
3. (A115) FUSED (B+) CIRCUIT OPEN OR HIGH RESISTANCE
1. Turn ignition off to the lock position.
2. Disconnect the ITBM C1 harness connector.
3. Check connectors - Clean/repair as necessary.
4. Using a 12-volt test light connected to ground, check the (A115) Fused (B+) circuit.
NOTE: Compare the brightness to that of a direct connection to the battery.
Does the test light illuminate brightly?
Yes
- Go To 4
No
- Repair the (A115) Fused (B+) circuit for a short to ground, an open circuit, or high resistance.
- Perform the ITBM VERIFICATION TEST. Integrated Trailer Brake Module (ITBM) Verification Test.
4. (Z905) GROUND CIRCUIT OPEN OR HIGH RESISTANCE
1. Turn ignition off to the lock position.
2. Using a 12-volt test light connected to B+, check the (Z905) Ground circuit.
NOTE: Compare the brightness to that of a direct connection to the battery.
Does the test light illuminate brightly?
Yes
- Go To 5
No
- Repair the (Z905) Ground circuit(s) for an open circuit or high resistance.
- Perform the ITBM VERIFICATION TEST. Integrated Trailer Brake Module (ITBM) Verification Test.
5. INTEGRATED TRAILER BRAKE MODULE (ITBM)
1. Turn ignition off to the lock position.
2. Using the wiring diagrams as a guide, check all related splices and connectors for signs of water intrusion, corrosion, pushed out or bent terminals, and correct pin tension. Pay particular attention to all Power and Ground circuits.
Were there any problems found?
Yes
- Repair as necessary.
- Perform the ITBM VERIFICATION TEST. Integrated Trailer Brake Module (ITBM) Verification Test.
No
- Replace the Integrated Trailer Brake Module (ITBM). Integrated Trailer Brake Module - Removal.
6. INTERMITTENT WIRING AND CONNECTORS
1. The conditions necessary to set this DTC are not present at this time.
2. Using the wiring diagrams as a guide, check all related splices and connectors for signs of water intrusion, corrosion, pushed out or bent terminals, and correct pin tension.
3. Wiggle test the wiring harness and connectors while monitoring the scan tool data relative to this circuit.
4. Look for the data to change or for the DTC to reset during the wiggle test.
5. While monitoring the scan tool data relative to this circuit.
6. Look for the data to change other than as expected or for the DTC to reset.
Were any problems found?
Yes
- Repair as necessary.
- Perform the ITBM VERIFICATION TEST. Integrated Trailer Brake Module (ITBM) Verification Test.
No
- Test complete, the condition or conditions that originally set this DTC are not present at this time.
- Perform the ITBM VERIFICATION TEST. Integrated Trailer Brake Module (ITBM) Verification Test.