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.
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HOMESERVICE MANUALSFORD2021TRANSIT-350 HD BASE, VAN CARGO EXTENDED, 3.5L ENG VIN 8, AWDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 601 (AUXILIARY BRAKE SYSTEM)DIAGNOSIS AND TESTINGAUXILIARY BRAKE SYSTEMDIAGNOSTIC TROUBLE CODE (DTC) CHARTNOTES
2021 Ford Transit-350 HD Base, Van Cargo Extended, 3.5L Eng VIN 8, AWD
Diagnostic Trouble Code (DTC) Chart: Notes
2021 Ford Transit-350 HD Base, Van Cargo Extended, 3.5L Eng VIN 8, AWDSECTION Notes
WARNING: This page is about a different car, the 2021 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.
Diagnostics in this article assume a certain skill level and knowledge of Ford-specific diagnostic practices. REFER to: Diagnostic Methods .
Diagnostic Trouble Code Chart
| Module | DTC | Description | Action |
|---|---|---|---|
| TBM | B148A:11 | Trailer Brake Output: Circuit Short To Ground | GO to Pinpoint Test C |
| TBM | B148A:12 | Trailer Brake Output: Circuit Short To Battery | GO to Pinpoint Test C |
| TBM | B148B:2A | Trailer Brake Manual Slider: Stuck in Range | GO to Pinpoint Test H |
| TBM | B148B:49 | Trailer Brake Manual Slider: Internal Electronic Failure | GO to Pinpoint Test H |
| TBM | B148C:2A | Trailer Brake Gain Button: Stuck in Range | GO to Pinpoint Test H |
| TBM | U064D:08 | Lost Communication with Trailer Brake Control Switch: Bus Signal/Message Failures | GO to Pinpoint Test H |
| TBM | U3000:12 | Control Module: Circuit Short To Battery | GO to Pinpoint Test C |
| TBM | U3000:1C | Control Module: Circuit Voltage Out Of Range | GO to Pinpoint Test C |
| TBM | U3000:1D | Control Module: Circuit Current Out Of Range | GO to Pinpoint Test C |
| TBM | U3003:16 | Battery Voltage: Circuit Voltage Below Threshold | GO to Pinpoint Test I |
| TBM | U3003:17 | Battery Voltage: Circuit Voltage Above Threshold | GO to Pinpoint Test J |
| TBM | U3008:13 | Control Module Ground "A": Circuit Open | GO to Pinpoint Test K |
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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.