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Ford U0100

00, U0121, U0140, and/or U0155 stored in the gear shift module (GSM). This may be due to the software in the GSM. To correct the condition,

DriveNot yet established by verified evidence.
ChargeNot yet established by verified evidence.
ServiceService contact is appropriate because Ford official service communications provide technical instructions for this documented condition. Urgency is not yet established by verified evidence.
Confidence95%

Quick answer

For certain 2021–2022 US Ford Mustang Mach-E vehicles, U0100:00 may be stored in the gear shift module (GSM), sometimes with U0121, U0140, and/or U0155. Ford technical communications state this may be due to GSM software.

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 U0100 mean?

For certain 2021–2022 US Ford Mustang Mach-E vehicles, U0100:00 may be stored in the gear shift module (GSM), sometimes with U0121, U0140, and/or U0155. Ford technical communications state this may be due to GSM software.

2. Technical explanation

The verified evidence identifies a Ford service scenario involving a Shift System Fault/Service Required condition, with U0103:87 stored in the secondary on-board diagnostic module (SOBDMC). In that scenario, U0100:00 may also be stored in the GSM, alongside U0121, U0140, and/or U0155. Ford states that the condition may be due to GSM software. The supplied evidence does not establish a universal meaning or single root cause for U0100 on every Ford vehicle or in every module.

3. What system is affected?

Verified evidence identifies the gear shift module (GSM) and, in the associated service scenario, the secondary on-board diagnostic module (SOBDMC).

4. How serious is this code?

Not yet established by verified evidence.

5. Symptoms you may notice

  • A Shift System Fault message is identified in the verified TSB evidence.
  • A Service Required message is identified in the verified TSB evidence.
  • U0103:87 may be stored in the SOBDMC.
  • U0100:00, U0121, U0140, and/or U0155 may be stored in the GSM.

6. Possible causes

  • Ford states that the condition may be due to software in the gear shift module (GSM).
  • Other 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 Ford dealer or qualified service facility using the applicable Ford technical instructions.
  • Record any instrument-panel messages and stored diagnostic trouble codes before service, if they can be read without disassembly or high-voltage work.
  • Do not attempt high-voltage repairs or module programming yourself.

10. Step-by-step troubleshooting

  1. Verify the vehicle model year and market applicability: supplied evidence applies to US-market 2021–2022 Ford Mustang Mach-E vehicles.
  2. Check whether the documented message and code pattern is present: Shift System Fault/Service Required, U0103:87 in the SOBDMC, and U0100:00 with possible U0121, U0140, and/or U0155 in the GSM.
  3. Have service personnel follow the applicable Ford technical instructions. Further diagnostic steps are not provided in the supplied verified evidence.

11. When to contact service

Service contact is appropriate because Ford official service communications provide technical instructions for this documented condition. Urgency is not yet established by verified evidence.

12. What the service center may check

  • Confirm stored DTC locations, including U0103:87 in the SOBDMC and U0100:00 in the GSM.
  • Confirm whether U0121, U0140, and/or U0155 are also stored in the GSM.
  • Assess whether the vehicle matches the applicable Ford Mustang Mach-E model-year and US-market coverage.
  • Follow the applicable Ford technical instructions for the GSM software-related condition.

13. Possible repair or resolution

  • Ford states that correction of the documented condition involves following its technical instructions; the supplied evidence indicates GSM software may be involved.
  • The precise repair or programming procedure is not included in the supplied verified evidence.

14. Affected vehicles

15. Related TSBs / service bulletins

  • TSB 25-2071, NHTSA Manufacturer Communication 11015681, published March 13, 2025. Evidence describes a Shift System Fault message, U0103:87 in the SOBDMC, and possible U0100:00, U0121, U0140, and/or U0155 in the GSM; it states GSM software may be involved.
  • TSB 21-2405, NHTSA Manufacturer Communication 10203653, published November 17, 2021. Evidence describes a Service Required condition with U0103:87 in the SOBDMC and possible U0100:00, U0121, U0140, and/or U0155 in the GSM; it states GSM software may be involved.
  • SSM 54574, NHTSA Manufacturer Communication 11028844, published February 12, 2026. It references U0100 stored in the ABS module with other codes and directs technicians to FSA 22P31 (US). Its applicability to the GSM scenario is not established by the supplied evidence.

16. Recall information

  • No recall is established by the supplied verified evidence.
  • SSM 54574 references FSA 22P31 (US), but the supplied evidence does not establish its scope, remedy, or applicability to the GSM-related U0100 condition.

17. Official manufacturer information

Official NHTSA-hosted manufacturer communications supplied: TSB 25-2071 (NHTSA ID 11015681), TSB 21-2405 (NHTSA ID 10203653), and SSM 54574 (NHTSA ID 11028844).

19. Frequently asked questions

What does U0100:00 indicate in this documented Mustang Mach-E scenario?

It is a DTC that may be stored in the GSM along with U0121, U0140, and/or U0155, in a Ford-documented Shift System Fault/Service Required scenario. The supplied evidence does not establish a broader universal interpretation for all U0100 occurrences.

What may cause this condition?

Ford states that the documented condition may be due to software in the GSM.

Which vehicles are supported by the supplied evidence?

US-market 2021–2022 Ford Mustang Mach-E vehicles. The supplied applicability data also contains a separate 2021 US entry.

Is it safe to drive or charge?

Not yet established by verified evidence.

Does the evidence identify a recall?

No recall is established by the supplied verified evidence.

20. Sources & verification

ReferenceVerified
Ford U0100: 00, U0121, U0140, and/or U0155 stored in the gear shift… | EV Diagnostics