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Cadillac U1126

- Do not replace the front camera. - Diagnose the CAN Bus 8 issue using SI 5199684

DriveNot yet established by verified evidence.
ChargeNot yet established by verified evidence.
ServiceService is appropriate because the verified manufacturer communication specifies a technician diagnostic path for CAN Bus 8. Driveability, charging status, and urgency are not established by the supplied evidence.
Confidence95%

Quick answer

For the specified Cadillac vehicles, U1126 is referenced in GM/Cadillac service communication PIT6503 as an example loss-of-communication DTC on CAN Bus 8. When the entire bus is affected, the bulletin instructs technicians not to replace the B174W Front View Camera module and to diagnose the CAN Bus 8 issue using SI 5199684.

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 U1126 mean?

For the specified Cadillac vehicles, U1126 is referenced in GM/Cadillac service communication PIT6503 as an example loss-of-communication DTC on CAN Bus 8. When the entire bus is affected, the bulletin instructs technicians not to replace the B174W Front View Camera module and to diagnose the CAN Bus 8 issue using SI 5199684.

2. Technical explanation

Verified evidence identifies U1126 as one of the loss-of-communication DTCs that may be set by the K56 Serial Data Gateway Module against ECUs on CAN Bus 8. The service communication directs technicians to check whether K56 has loss-of-communication DTCs for other ECUs on CAN Bus 8. If the entire bus is impacted, diagnosis is to focus on the CAN Bus 8 issue under SI 5199684 rather than replacing the front camera.

3. What system is affected?

CAN Bus 8 communication network; K56 Serial Data Gateway Module. The bulletin also specifically references the B174W Front View Camera module.

4. How serious is this code?

Not yet established by verified evidence.

5. Symptoms you may notice

  • A U1126 DTC may be present.
  • The K56 Serial Data Gateway Module may also set loss-of-communication DTCs against other ECUs on CAN Bus 8. Further customer-visible symptoms are not yet established by verified evidence.

6. Possible causes

  • A CAN Bus 8 issue when the entire bus is impacted.
  • Specific underlying wiring, connector, module, power, ground, or software causes are 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 qualified Cadillac service facility or technician using the applicable service information.
  • Provide the stored DTCs and ask whether K56 has loss-of-communication DTCs for other ECUs on CAN Bus 8.
  • Do not treat U1126 alone as verified evidence that the front camera requires replacement.

10. Step-by-step troubleshooting

  1. Technicians should check whether the K56 Serial Data Gateway Module is also setting loss-of-communication DTCs against other ECUs on CAN Bus 8.
  2. Examples named in the service communication are U1126, U1127, U0235, and U1616.
  3. If the entire CAN Bus 8 is impacted, diagnose the CAN Bus 8 issue using SI 5199684.
  4. If the entire bus is impacted, do not replace the B174W Front View Camera module as the response described by PIT6503.

11. When to contact service

Service is appropriate because the verified manufacturer communication specifies a technician diagnostic path for CAN Bus 8. Driveability, charging status, and urgency are not established by the supplied evidence.

12. What the service center may check

  • Check for K56 Serial Data Gateway Module loss-of-communication DTCs involving other ECUs on CAN Bus 8.
  • Determine whether the entire CAN Bus 8 is impacted.
  • Use SI 5199684 to diagnose the CAN Bus 8 issue when the entire bus is impacted.

13. Possible repair or resolution

  • For the entire-bus condition described in PIT6503, do not replace the B174W Front View Camera module.
  • The final repair is not established by the supplied verified evidence; it depends on diagnosis under SI 5199684.

14. Affected vehicles

15. Related TSBs / service bulletins

  • PIT6503C, NHTSA Manufacturer Communication 11036219, published August 12, 2026: directs checking K56 for other CAN Bus 8 loss-of-communication DTCs and, if the entire bus is impacted, not replacing B174W and diagnosing CAN Bus 8.
  • PIT6503B, NHTSA Manufacturer Communication 11034014, published June 17, 2026: same documented diagnostic direction.
  • PIT6503A, NHTSA Manufacturer Communication 11033726, published June 3, 2026: directs diagnosis of CAN Bus 8 using SI 5199684 and advises against front-camera replacement when the entire bus is impacted.
  • PIT6503, NHTSA Manufacturer Communication 11031514, published April 14, 2026: directs diagnosis of CAN Bus 8 using SI 5199684 and advises against front-camera replacement when the entire bus is impacted.

16. Recall information

  • No recall information was supplied in the verified evidence.

17. Official manufacturer information

Verified manufacturer communication applies to US-market Cadillac CELESTIQ 2024-2026, LYRIQ 2024-2026, OPTIQ 2024-2026, and VISTIQ 2024-2026. An additional applicability record lists LYRIQ 2024-2025. Source: NHTSA-hosted GM/Cadillac manufacturer communications PIT6503 through PIT6503C.

19. Frequently asked questions

Does U1126 mean the front camera must be replaced?

No. For the condition in which the entire CAN Bus 8 is impacted, PIT6503 directs technicians not to replace the B174W Front View Camera module.

What should be checked with U1126?

The service communication directs technicians to check whether the K56 Serial Data Gateway Module is also setting loss-of-communication DTCs against other ECUs on CAN Bus 8.

Which other codes are mentioned by the bulletin?

The bulletin gives U1126, U1127, U0235, and U1616 as examples of CAN Bus 8 loss-of-communication DTCs.

Is it safe to drive or charge with U1126?

Not yet established by verified evidence.

20. Sources & verification

Verified
Cadillac U1126: - Do not replace the front camera. - Diagnose the CAN… | EV Diagnostics