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Ford P0C78

10C666-C 1 High Voltage Battery Junction Box (

DriveNot yet established by verified evidence.
ChargeNot yet established by verified evidence.
ServiceService is appropriate because P0C78 is listed in Ford TSB 24-2017 with MIL and/or powertrain malfunction indicator conditions. The supplied evidence does not establish urgency, drivability, or charging status.
Confidence95%

Quick answer

For 2021–2022 Ford Mustang Mach-E vehicles in the US, DTC P0C78 is documented in Ford TSB 24-2017 in connection with the high-voltage battery junction box. The supplied evidence does not establish whether the vehicle is safe to drive or charge.

This page separates verified manufacturer/regulator evidence from supporting material. Unsupported causes, repairs or safety conclusions are not guessed.

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1. What does P0C78 mean?

For 2021–2022 Ford Mustang Mach-E vehicles in the US, DTC P0C78 is documented in Ford TSB 24-2017 in connection with the high-voltage battery junction box. The supplied evidence does not establish whether the vehicle is safe to drive or charge.

2. Technical explanation

The verified diagnostic record identifies P0C78 with the text “10C666-C 1 High Voltage Battery Junction Box (”. Ford TSB 24-2017 lists P0C78 among DTCs that may be present with an illuminated malfunction indicator lamp (MIL) and/or powertrain malfunction (wrench) indicator. The bulletin evidence references high-voltage battery junction box service part LK9Z-10C666-C.

3. What system is affected?

High-voltage battery junction box, based on the verified diagnostic title and Ford TSB 24-2017 evidence.

4. How serious is this code?

Unknown. The supplied verified evidence does not assign a severity level to P0C78.

5. Symptoms you may notice

  • Illuminated malfunction indicator lamp (MIL), as documented in Ford TSB 24-2017.
  • Powertrain malfunction (wrench) indicator, as documented in Ford TSB 24-2017.

6. Possible causes

  • A specific underlying cause is not yet established by the supplied verified evidence.
  • Ford TSB 24-2017 identifies the high-voltage battery junction box as a referenced service part in cases involving P0C78.

7. Can I still drive the vehicle?

Not yet established by verified evidence.

8. Can I charge the vehicle?

Not yet established by verified evidence.

9. What you can safely do

  • Arrange diagnosis by a Ford dealer or qualified EV service provider.
  • Do not attempt high-voltage battery junction box repair or disassembly yourself.
  • Record any warning indicators and diagnostic codes shown by the vehicle.

10. Step-by-step troubleshooting

  1. Have a qualified service provider retrieve and document all stored DTCs.
  2. Refer the service provider to Ford TSB 24-2017 and NHTSA manufacturer communication 10249760.
  3. No further troubleshooting procedure is established by the supplied verified evidence.

11. When to contact service

Service is appropriate because P0C78 is listed in Ford TSB 24-2017 with MIL and/or powertrain malfunction indicator conditions. The supplied evidence does not establish urgency, drivability, or charging status.

12. What the service center may check

  • Retrieve all diagnostic trouble codes.
  • Review Ford TSB 24-2017 for applicable 2021–2022 US Mustang Mach-E vehicles.
  • Evaluate the high-voltage battery junction box in accordance with Ford service information. Specific test steps are not included in the supplied evidence.

13. Possible repair or resolution

  • Ford TSB 24-2017 references high-voltage battery junction box service part LK9Z-10C666-C.
  • The exact repair decision, conditions, and procedure are not established by the supplied verified evidence.

14. Affected vehicles

15. Related TSBs / service bulletins

  • Ford TSB 24-2017, published January 26, 2024; NHTSA manufacturer communication 10249760. It lists P0C78 among DTCs associated with an illuminated MIL and/or powertrain malfunction (wrench) indicator and references high-voltage battery junction box part LK9Z-10C666-C.

16. Recall information

  • No recall information was supplied or established by verified evidence.

17. Official manufacturer information

Official source: NHTSA Manufacturer Communication PDF 10249760, Ford TSB 24-2017: https://static.nhtsa.gov/odi/tsbs/2024/MC-10249760-0001.pdf

19. Frequently asked questions

What does P0C78 mean on a Ford Mustang Mach-E?

The supplied verified record associates P0C78 with “10C666-C 1 High Voltage Battery Junction Box (” and Ford TSB 24-2017 references the high-voltage battery junction box.

Which vehicles are covered by the supplied evidence?

The verified applicability record identifies 2021–2022 Ford Mustang Mach-E vehicles in the US.

Can I drive or charge with P0C78?

Not yet established by verified evidence.

Is there a Ford service bulletin for P0C78?

Yes. Ford TSB 24-2017, NHTSA manufacturer communication 10249760, lists P0C78 among the applicable DTCs.

20. Sources & verification

ReferenceAccepted ResearchVerified
Ford P0C78: 10C666-C 1 High Voltage Battery Junction Box ( | EV Diagnostics