The diagnostic trouble code (DTC) P1674 can illuminate the malfunction indicator lamp (MIL) in some 2020-2022 Ford F-Super Duty trucks equipped with a 6.7L engine. This code is often associated with a discharged battery or a low battery state of charge.
Understanding DTC P1674 in Ford F-Super Duty
The P1674 code indicates a potential issue with the transmission control module (TCM) communication due to insufficient battery power. While this might seem counterintuitive, a low battery voltage can disrupt the complex electronic systems within modern vehicles, leading to unexpected errors.
The TCM relies on a stable voltage supply for proper operation. When the battery is discharged or nearing the end of its lifespan, the voltage fluctuations can interfere with the TCM’s ability to communicate with other modules in the vehicle. This can trigger the P1674 code and illuminate the MIL.
Diagnosing and Resolving DTC P1674
Before diving into complex diagnostic procedures outlined in the Workshop Manual (WSM), Section 307-01, it’s crucial to address the potential root cause: the battery.
Step 1: Battery Testing and Replacement
- Charge the Battery: Ensure the battery is fully charged before proceeding with any testing.
- Test the Battery: Utilize a Ford-approved battery tester, as specified in the Ford Warranty and Policy Manual. This specialized equipment will accurately assess the battery’s health and state of charge.
- Replace if Necessary: If the test indicates a faulty or significantly discharged battery, replace it with a new one meeting Ford’s specifications.
Step 2: Clearing the DTC and Self-Test
- Clear DTCs: After replacing the battery (if needed), clear the diagnostic trouble codes using a suitable OBDII scan tool.
- Perform Self-Test: Run the vehicle’s self-test diagnostics again to see if the P1674 code returns.
Step 3: Further Diagnostics (if P1674 Persists)
- Consult WSM Section 307-01: If the P1674 code reappears after addressing the battery, refer to the detailed diagnostic procedures outlined in WSM, Section 307-01. This section provides comprehensive troubleshooting steps to pinpoint the underlying cause.
Step 4: Report to Ford (if P1674 is Resolved)
- Submit a Report via OASIS: If the P1674 code does not return after battery replacement and clearing the DTC, it’s helpful to report this to Ford through the “Report a Vehicle Concern” link on the OASIS website. This information assists Ford’s engineering team in ongoing investigations and potential product improvements.
Affected Ford F-Super Duty Models
The following Ford F-Super Duty models equipped with a 6.7L engine may be affected by DTC P1674:
- F-250 Super Duty (2020-2022)
- F-350 Super Duty (2020-2022)
- F-450 Super Duty (2020-2022)
- F-550 Super Duty (2020-2022)
Ford F-Super Duty Trucks
Conclusion
DTC P1674 in a Ford F-Super Duty often points to a battery issue. By systematically checking and addressing the battery’s health, you can resolve this code and prevent unnecessary deeper diagnostic work. Remember to consult official Ford documentation for comprehensive troubleshooting procedures. Reporting resolved instances of P1674 through OASIS contributes valuable data to Ford’s engineering efforts.
