Cadillac P0C78
Added Chart and 2025 Model Year
Quick answer
P0C78 is referenced in Cadillac bulletin 23-NA-151 for certain US Cadillac LYRIQ and VISTIQ vehicles. The supplied verified evidence does not establish a component-level definition, symptoms, driving or charging status, or a specific repair for P0C78.
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?
P0C78 is referenced in Cadillac bulletin 23-NA-151 for certain US Cadillac LYRIQ and VISTIQ vehicles. The supplied verified evidence does not establish a component-level definition, symptoms, driving or charging status, or a specific repair for P0C78.
2. Technical explanation
The supplied diagnostic record labels P0C78 as “Added Chart and 2025 Model Year.” However, the verified bulletin summaries show that this wording describes a revision to GM bulletin 23-NA-151, not a technical definition of the DTC. The bulletin revision history states that P0C78 was added on August 1, 2024, and that a chart and 2025 model-year coverage were added on August 14, 2024. A later April 2025 revision summary continues to list P0C78 among the bulletin’s additional SI keywords. No P0C78 fault logic, monitored circuit, threshold, or component is established by the supplied evidence.
3. What system is affected?
Not yet established by verified evidence.
4. How serious is this code?
Unknown. The supplied diagnostic record lists severity as unknown.
5. Symptoms you may notice
- Not yet established by verified evidence.
6. Possible causes
- Not yet established by verified evidence.
7. Can I still drive the vehicle?
Unknown. The supplied diagnostic record lists safe-to-drive status as unknown.
8. Can I charge the vehicle?
Unknown. The supplied diagnostic record lists safe-to-charge status as unknown.
9. What you can safely do
- Arrange diagnosis by a Cadillac/GM service professional using applicable GM service information.
- Do not attempt high-voltage battery, cable, connector, or isolation-related repairs based on this page.
10. Step-by-step troubleshooting
- Confirm the exact DTC and any accompanying DTCs with an appropriate diagnostic scan tool.
- Refer the vehicle to Cadillac/GM service personnel for diagnosis under bulletin 23-NA-151 if the vehicle and concern fall within the bulletin’s applicable service context.
- Not yet established by verified evidence: a user-performable P0C78 diagnostic sequence.
11. When to contact service
Service need is listed as unknown in the supplied diagnostic record. Cadillac/GM service evaluation is appropriate because P0C78 is included in official GM bulletin 23-NA-151.
12. What the service center may check
- Review GM bulletin 23-NA-151 and the applicable GM service information for the vehicle.
- Check for accompanying DTCs; the supplied April 2025 bulletin summary identifies U2426, U2427, U35B5, P0AA6, U359E, P0AE3, U1666, U1667, U2BFC, and P1C34 as additional SI keywords or referenced DTCs in the bulletin summary.
- The supplied April 2025 bulletin summary also mentions pack damage and SPS data-dump capture, but does not establish that either condition applies to every P0C78 occurrence.
13. Possible repair or resolution
- Not yet established by verified evidence.
14. Affected vehicles
- Cadillac LYRIQ · 2023–2026 · US
- Cadillac LYRIQ · 2023–2025 · US
- Cadillac VISTIQ · 2023–2026 · US
15. Related TSBs / service bulletins
- GM/Cadillac bulletin 23-NA-151, published through NHTSA as manufacturer communication MC-11017886 on April 9, 2025. Its supplied summary lists P0C78 among additional SI keywords and notes revisions involving certain DTCs, pack-damage mention, and SPS data-dump capture.
- GM/Cadillac bulletin 23-NA-151, published through NHTSA as MC-11012693 on December 11, 2024. Its supplied summary states that P0C78 was added on August 1, 2024 and that a chart and 2025 model-year coverage were added on August 14, 2024.
- GM/Cadillac bulletin 23-NA-151, published through NHTSA as MC-11011944 on November 20, 2024, with the same supplied revision-history evidence concerning P0C78.
- GM/Cadillac bulletin 23-NA-151, published through NHTSA as MC-11008903 on August 14, 2024. Its supplied summary states that P0C78 was added on August 1, 2024 and that a chart and 2025 model-year coverage were added on August 14, 2024.
16. Recall information
- Not yet established by verified evidence.
17. Official manufacturer information
Official NHTSA-hosted GM manufacturer communications for bulletin 23-NA-151: https://static.nhtsa.gov/odi/tsbs/2025/MC-11017886-0001.pdf and https://static.nhtsa.gov/odi/tsbs/2024/MC-11008903-0001.pdf
- NHTSA: NHTSA Manufacturer Communication PDF 11008903: 23-NA-151 · official_tsb
- NHTSA: NHTSA Manufacturer Communication PDF 11011944: 23-NA-151 · official_tsb
- NHTSA: NHTSA Manufacturer Communication PDF 11012693: 23-NA-151 · official_tsb
- NHTSA: NHTSA Manufacturer Communication PDF 11017886: 23-NA-151 · official_tsb
19. Frequently asked questions
What does Cadillac P0C78 mean?
The supplied diagnostic record labels it “Added Chart and 2025 Model Year,” but verified bulletin evidence indicates this is bulletin revision wording rather than a technical DTC definition. A component-level meaning is not yet established by verified evidence.
Which vehicles are listed as applicable?
The supplied applicability data lists US Cadillac LYRIQ model years 2023–2026 and US Cadillac VISTIQ model years 2023–2026. It also contains an overlapping LYRIQ entry for 2023–2025.
Is P0C78 covered by a service bulletin?
Yes. P0C78 is listed in supplied summaries for GM bulletin 23-NA-151. The evidence does not establish that every P0C78 event has the same cause or repair.
Can I drive or charge with P0C78?
Not yet established by verified evidence. The supplied diagnostic record marks both safe-to-drive and safe-to-charge status as unknown.