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Mitsubishi P1B78

Return to Step 1. NO : The diagnosis is complete. DTC U111C BMU CAN Timeout CAUTION If there is any problem in the CAN bus lines, an incorrect DTC may be set. Prior to this diagnos

DriveNot yet established by verified evidence.
ChargeNot yet established by verified evidence.
ServiceService involvement is supported by the official bulletin procedure because it includes BMU replacement when P1B78 is stored. Driving and charging restrictions are not established by the supplied evidence.
Confidence95%

Quick answer

P1B78 is documented in Mitsubishi service bulletin diagnostic procedures for 2014 and 2016 US-market i-MiEV vehicles. The supplied evidence does not establish a plain-language fault definition for P1B78, driving safety, charging safety, or severity.

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 P1B78 mean?

P1B78 is documented in Mitsubishi service bulletin diagnostic procedures for 2014 and 2016 US-market i-MiEV vehicles. The supplied evidence does not establish a plain-language fault definition for P1B78, driving safety, charging safety, or severity.

2. Technical explanation

The verified Mitsubishi/NHTSA bulletin evidence places P1B78 in an EV-ECU diagnostic routine. After the DTC is erased, the procedure calls for connecting a quick-charging connector/gun or external power-supply equipment and checking whether P1B78 returns. If it returns, the procedure directs a return to Step 1; if it does not return, the diagnosis is complete. One supplied bulletin excerpt also states: if P1B78 is stored, replace the BMU, then proceed to the recheck step.

3. What system is affected?

Battery Management Unit (BMU) and EV-ECU diagnostic process are referenced by the verified evidence. The exact P1B78 system definition is not yet established by verified evidence.

4. How serious is this code?

Not yet established by verified evidence.

5. Symptoms you may notice

  • A verified symptom specifically attributable to P1B78 is not yet established by the supplied evidence.

6. Possible causes

  • Not yet established by verified evidence.

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 Mitsubishi-qualified EV service facility.
  • Do not attempt high-voltage battery or BMU repair yourself.
  • Provide the stored P1B78 code and vehicle model year to the service facility.

10. Step-by-step troubleshooting

  1. Verified service procedure: erase the stored DTC, connect the quick-charging gun/connector or external power-supply equipment, then check whether P1B78 is stored or set again.
  2. If P1B78 returns during the verified procedure, the bulletin directs technicians to return to Step 1 of its diagnostic routine.
  3. If P1B78 does not return, the bulletin states that the diagnosis is complete.
  4. The detailed Step 1 diagnostic instructions are not included in the supplied evidence.

11. When to contact service

Service involvement is supported by the official bulletin procedure because it includes BMU replacement when P1B78 is stored. Driving and charging restrictions are not established by the supplied evidence.

12. What the service center may check

  • Confirm whether P1B78 is stored in the EV-ECU.
  • Erase the DTC and perform the bulletin's charging/external-power recheck.
  • If P1B78 is stored, the supplied TSB excerpt directs replacement of the BMU, followed by a DTC recheck.
  • Verify whether P1B78 returns after the prescribed recheck.

13. Possible repair or resolution

  • The supplied official TSB evidence directs BMU replacement when P1B78 is stored, followed by the specified DTC recheck.
  • No further repair outcome is established by the supplied evidence.

14. Affected vehicles

15. Related TSBs / service bulletins

  • TSB-19-54-004, published March 13, 2019, NHTSA Manufacturer Communication PDF 10158409.
  • TSB-19-54-005, published March 13, 2019, NHTSA Manufacturer Communication PDF 10158410.

16. Recall information

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

17. Official manufacturer information

Official NHTSA-hosted Mitsubishi communications: https://static.nhtsa.gov/odi/tsbs/2019/MC-10158409-9999.pdf and https://static.nhtsa.gov/odi/tsbs/2019/MC-10158410-9999.pdf

19. Frequently asked questions

What does P1B78 mean on a Mitsubishi i-MiEV?

The supplied verified evidence does not provide a plain-language definition of P1B78. It documents an EV-ECU diagnostic and recheck procedure and, when P1B78 is stored, directs BMU replacement.

Which vehicles are covered by the supplied evidence?

2014 and 2016 Mitsubishi i-MiEV vehicles in the US market.

Can P1B78 be cleared and ignored?

The verified procedure requires a recheck after erasing the DTC. If P1B78 returns, the bulletin directs technicians back to the diagnostic procedure; it does not establish that the code should be ignored.

Is P1B78 related to U111C?

The supplied bulletin excerpts discuss U111C BMU CAN Timeout near the P1B78 procedure, but they do not establish that P1B78 and U111C have the same cause or are inherently linked.

20. Sources & verification

Verified
Mitsubishi P1B78: Return to Step 1. NO : The diagnosis is complete.… | EV Diagnostics