Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Pinpoint Test I: U3003:16
- Refer to TRAILER/CAMPER ADAPTER
for schematic and connector information.
Normal Operation and Fault Conditions
The TRM requires an operating voltage between 9 and 16 volts. The TRM receives this voltage from the BCMC. The TRM has a single ground circuit. Excessive resistance or an open in one or more of these circuits, a discharged battery or a inoperative charging system results in the TRM setting a DTC. If the voltage drops below 8 volts the TRM disables the trailer brake output and shuts down.
REFER to: Auxiliary Brake System - System Operation and Component Description .
DTC Fault Trigger Conditions
DTC Description Fault Trigger Condition TBM U3003:16 Battery Voltage: Circuit Voltage Below Threshold This DTC sets in continuous memory and on-demand if the voltage supplied to the TRM is less than 9 volts for longer than 5 minutes while not braking. Possible Sources
- Fuses
- Wiring, terminals or connectors
- Charging system concern
- Battery
- TRM
Visual Inspection and Pre-checks
- Make sure the vehicle battery terminals and cables are free of any corrosion and other contaminants.
- Make sure the vehicle battery terminals are tightened to their correct torque specifications.
- Make sure BCMC fuse 42 (30A) is OK.
- NOTE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may cause damage to the connector.
- I1 RECHECK THE TBM (TRAILER BRAKE CONTROL MODULE) DIAGNOSTIC TROUBLE CODES (DTCS)NOTE: The TRM is a combined TBM and Trailer Lighting Module.
- Using a diagnostic scan tool, clear the TBM Diagnostic Trouble Codes (DTCs).
- Ignition OFF.
- Ignition ON.
- Using a diagnostic scan tool, carry out the TBM self-test.
Is DTC U3003:16 still present?
Yes GO to I2 No The system is operating correctly at this time. The DTC may have set due to a previous low battery voltage condition. - I2 CHECK FOR CHARGING SYSTEM DIAGNOSTIC TROUBLE CODES (DTCS) IN THE PCM (POWERTRAIN CONTROL MODULE)
- Using a diagnostic scan tool, retrieve all Continuous Memory Diagnostic Trouble Codes (CMDTCs).
Is DTC B1317, B1318, B1676, U3003:16 or U3003:17 present in one or more modules AND are any charging system Diagnostic Trouble Codes (DTCs) present in the PCM?
Yes DIAGNOSE the charging system concern. No GO to I3 - I3 CHECK THE BATTERY CONDITION AND STATE OF CHARGE
- Carry out the Battery Condition Test pinpoint test. REFER to: Battery .
Did the battery pass the condition test?
Yes GO to I4 No INSTALL a new battery. REFER to: Battery . - I4 CHECK THE TRM (TRAILER MODULE) VOLTAGE SUPPLY FOR AN OPEN
- Ignition OFF.
- Disconnect TRM C2498C.
- Remove BCMC fuse 42 (30A).
- Measure:
Positive Lead Measurement / Action Negative Lead C2498C-13 BCMC fuse 42 (30A) output side
Is the resistance less than 3 ohms?
Yes GO to I5 No VERIFY BCMC fuse 42 (30A) is OK. If OK, REPAIR the circuit. If not OK, REFER to the OEM WIRING DIAGRAMS to identify the cause of the circuit short. - I5 CHECK THE TRM (TRAILER MODULE) GROUND CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect the battery negative cable. REFER to: Battery Disconnect and Connect .
- Measure:
Positive Lead Measurement / Action Negative Lead C2498F-12 Ground
Is the resistance less than 3 ohms?
Yes GO to I6 No REPAIR the circuit. - I6 CHECK FOR CORRECT TRM (TRAILER MODULE) OPERATION
- Disconnect TRM C2498C (if not previously disconnected).
- Using a good light source, inspect the connector for the following:
- corrosion - install new connector or terminal and clean the module pins
- damaged or bent pins - install new terminals or pins
- pushed-out pins - install new pins as necessary
- spread terminals - install new terminals as necessary
- Connect TRM C2498C, make sure it seats and latches correctly.
- Connect the battery negative cable (if previously disconnected). REFER to: Battery Disconnect and Connect .
- Install BCMC fuse 42 (30A).
- Operate the system and verify the concern is still present.
Is the concern still present?
Yes CHECK OASIS for any applicable service articles: TSB, GSB, SSM or FSA. If a service article exists for this concern, DISCONTINUE this test and FOLLOW the service article instructions. If no service articles address this concern, INSTALL a new TRM module. REFER to: Trailer Module (TRM) . No The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. ADDRESS the root cause of any connector or pin issues.
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.