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 138 (AUXILIARY BRAKE SYSTEM)
2021 Ford Transit-350 HD Base, Van Cargo Extended, 3.5L Eng VIN 8, AWD
Section 138 (Auxiliary Brake System)
2021 Ford Transit-350 HD Base, Van Cargo Extended, 3.5L Eng VIN 8, AWDSECTION Section 138 (Auxiliary Brake System)
WARNING: This page is about a different car, the 2018 Ford F-550 Super Duty, 2018 Ford F-450 Super Duty, 2018 Ford F-350 Super Duty, and 2018 Ford F-250 Super Duty. However, it is still accessible from the selected car via links, so may be relevant.
- Description And Operation
- Diagnosis And Testing
- Auxiliary Brake System - Vehicles With: Trailer Brake Control
- DTC Chart: Trailer Brake Control Module (TBM)
- Symptom Chart: Trailer Brake System
- Pinpoint Tests
- Pinpoint Test A : The Trailer Brakes Are Inoperative
- Pinpoint Test B : The Trailer Brakes Are Always Engaged
- Pinpoint Test C : The Message Center Displays Wiring Fault On Trailer
- Pinpoint Test D : The Message Center Does Not Agree With Actual Trailer Connection
- Pinpoint Test E : U3003:17
- Pinpoint Test F : U3003:16
- Pinpoint Test G : U3008:13
- Pinpoint Test H : U0100:00
- Pinpoint Test I : U0121:00
- Pinpoint Test J : U0140:00
- Pinpoint Test K : U0155:00
- Auxiliary Brake System - Vehicles With: Trailer Brake Control
- Removal And Installation
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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.