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Chevrolet U1643

G111 and/or G112 may not be properly torqued. Correction: Inspect G111 and G112 to confirm they are torq

DriveNot yet established by verified evidence.
ChargeNot yet established by verified evidence.
ServiceService is appropriate when U1643 is stored, especially if there is a no-start with a clicking starter or multiple communication-loss DTCs. GM bulletins provide technician-directed inspection and CAN bus diagnostic guidance.
Confidence95%

Quick answer

For certain U.S. Chevrolet Blazer and Equinox vehicles, DTC U1643 is included in a GM bulletin involving G111 and/or G112 ground connections that may not be properly torqued. The bulletin directs inspection of those grounds to confirm correct torque.

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 U1643 mean?

For certain U.S. Chevrolet Blazer and Equinox vehicles, DTC U1643 is included in a GM bulletin involving G111 and/or G112 ground connections that may not be properly torqued. The bulletin directs inspection of those grounds to confirm correct torque.

2. Technical explanation

Verified GM/NHTSA manufacturer communications identify U1643 among DTCs that may be present when G111 and/or G112 may not be properly torqued. Separately, GM communications PIT6503/PIT6503A/PIT6503B list U1643 as an example of a loss-of-communication DTC on CAN Bus 2. Those communications direct technicians to check whether the K56 Serial Data Gateway Module is also setting communication-loss DTCs against other ECUs; where multiple ECUs are affected, they state not to replace the B174W Front View Camera module and to diagnose the CAN bus concern.

3. What system is affected?

Verified evidence associates U1643 with G111/G112 ground connections and, in separate GM communications, CAN Bus 2 communication diagnosis involving the K56 Serial Data Gateway Module. A single definitive affected system for every U1643 occurrence 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 no-start condition with a clicking starter when the Start button is pressed is identified in GM bulletin PIT6282/PIT6282A as a condition in which U1643 may be present.
  • GM PIT6503-series communications describe U1643 as an example of a loss-of-communication DTC on CAN Bus 2.

6. Possible causes

  • G111 and/or G112 may not be properly torqued, according to GM bulletins PIT6282 and PIT6282A.
  • For a vehicle with U1643 and multiple ECU communication-loss DTCs, GM directs diagnosis of the CAN bus concern. The specific underlying CAN bus fault is not established by the supplied 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 Chevrolet/GM-qualified service facility, particularly if the vehicle has a no-start condition.
  • Provide the complete stored-DTC list to the service facility, including any communication-loss codes.
  • Do not replace the front camera based on U1643 alone when multiple ECUs have CAN Bus 2 communication-loss DTCs; GM's PIT6503-series communications specifically advise against front-camera replacement in that situation.

10. Step-by-step troubleshooting

  1. A qualified technician should inspect G111 and G112 to confirm they are correctly torqued, as directed by GM PIT6282/PIT6282A.
  2. For U1643 accompanied by communication-loss DTCs, GM directs checking whether the K56 Serial Data Gateway Module is setting communication-loss DTCs against other ECUs on CAN Bus 2.
  3. If multiple ECUs are affected, GM directs diagnosis of the CAN bus concern rather than replacement of the B174W Front View Camera module.

11. When to contact service

Service is appropriate when U1643 is stored, especially if there is a no-start with a clicking starter or multiple communication-loss DTCs. GM bulletins provide technician-directed inspection and CAN bus diagnostic guidance.

12. What the service center may check

  • Retrieve and review all stored DTCs.
  • Inspect G111 and G112 and confirm correct torque, per PIT6282/PIT6282A.
  • Determine whether the K56 Serial Data Gateway Module has communication-loss DTCs against other ECUs on CAN Bus 2.
  • If multiple ECUs show communication loss, diagnose the CAN bus concern.
  • Avoid replacing the B174W Front View Camera module solely for an entire-bus/multiple-ECU communication-loss condition, per PIT6503-series guidance.

13. Possible repair or resolution

  • Confirming correct torque at G111 and G112 is the correction identified in GM PIT6282/PIT6282A.
  • For a multiple-ECU CAN Bus 2 communication-loss condition, the final repair is not established by the supplied verified evidence; GM directs CAN bus diagnosis and advises against front-camera replacement in that scenario.

14. Affected vehicles

15. Related TSBs / service bulletins

  • GM PIT6282, published November 12, 2024 (NHTSA MC-11011192): identifies U1643 among codes that may accompany a clicking-starter no-start; states G111 and/or G112 may not be properly torqued and directs inspection to confirm torque.
  • GM PIT6282A, published November 18, 2024 (NHTSA MC-11011319): revised communication with the same verified U1643, clicking-starter no-start, and G111/G112 torque information.
  • GM PIT6503, published April 14, 2026 (NHTSA MC-11031514): lists U1643 as an example CAN Bus 2 communication-loss DTC and directs CAN bus diagnosis when multiple ECUs are affected.
  • GM PIT6503A, published June 3, 2026 (NHTSA MC-11033726): revised CAN Bus 2 communication diagnostic guidance involving U1643.
  • GM PIT6503B, published June 17, 2026 (NHTSA MC-11034014): revised CAN Bus 2 communication diagnostic guidance involving U1643.

16. Recall information

  • Not yet established by verified evidence.

17. Official manufacturer information

Official NHTSA-hosted GM communications: PIT6282/PIT6282A and PIT6503/PIT6503A/PIT6503B. The supplied records identify applicability to U.S. Chevrolet Blazer model years 2024-2026 and Chevrolet Equinox model years 2024-2026; duplicated 2025 Equinox applicability entries are present in the supplied data.

19. Frequently asked questions

What does Chevrolet U1643 mean in the supplied bulletin evidence?

GM PIT6282/PIT6282A lists U1643 among DTCs that may be present when G111 and/or G112 may not be properly torqued.

Can U1643 be related to a no-start?

Yes. GM PIT6282/PIT6282A identifies a no-start with a clicking starter when the Start button is pressed as a condition in which U1643 may be present.

Does U1643 mean the front camera should be replaced?

No, not when the entire CAN Bus 2 is affected with communication loss at multiple ECUs. GM PIT6503-series communications specifically direct technicians not to replace the B174W Front View Camera module in that situation.

Is it safe to drive or charge with U1643?

Not yet established by verified evidence.

20. Sources & verification

Verified
Chevrolet U1643: G111 and/or G112 may not be properly torqued.… | EV Diagnostics