Jeep U0129
If multiple LOC DTCs are present: a. Check battery health, system voltage, and TCM (including
Quick answer
For applicable 2024–2026 US Jeep Grand Cherokee and Wagoneer vehicles, U0129 is listed in an official Jeep service communication concerning multiple LOC DTCs. When multiple LOC DTCs are present, the communication directs checks of battery health, system voltage, and the TCM. The supplied evidence does not establish a complete U0129 definition or a vehicle-specific repair.
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 U0129 mean?
For applicable 2024–2026 US Jeep Grand Cherokee and Wagoneer vehicles, U0129 is listed in an official Jeep service communication concerning multiple LOC DTCs. When multiple LOC DTCs are present, the communication directs checks of battery health, system voltage, and the TCM. The supplied evidence does not establish a complete U0129 definition or a vehicle-specific repair.
2. Technical explanation
NHTSA Manufacturer Communication 11021842 (Jeep service communication 9100641) lists U0129 among relevant codes in a multiple-LOC-DTC diagnostic context. The verified excerpt states that if multiple modules report the same LOC, the ESM is not the cause because it is not a gateway module. It further states that, when multiple LOC DTCs are present, battery health, system voltage, and the TCM should be checked. The remainder of the TCM instruction is not included in the supplied evidence.
3. What system is affected?
Multiple-module loss-of-communication (LOC) diagnostic context. The supplied evidence specifically references battery health, system voltage, TCM, and ESM; it does not establish a complete affected-system description for U0129 alone.
4. How serious is this code?
Not yet established by verified evidence.
5. Symptoms you may notice
Not yet established by verified evidence.
6. Possible causes
- When multiple LOC DTCs are present, the official communication identifies battery health, system voltage, and the TCM as items to check.
- The ESM is not identified as the cause when multiple modules report the same LOC, because the communication states that the ESM is not a gateway module.
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
- Record all stored DTCs and note whether multiple LOC DTCs are present.
- Arrange diagnosis using the applicable Jeep service information or a qualified service facility.
- Do not assume the ESM is the cause solely because multiple modules report the same LOC.
10. Step-by-step troubleshooting
- Confirm whether U0129 occurs with multiple LOC DTCs.
- Check battery health.
- Check system voltage.
- Check the TCM as directed by the applicable service communication. The supplied evidence does not include the complete TCM procedure.
- If multiple modules report the same LOC, recognize that the communication states the ESM is not the cause because it is not a gateway module.
11. When to contact service
Service is recommended for diagnosis if U0129 is present with multiple LOC DTCs. The verified evidence does not establish urgency, drivability, charging status, or a specific repair.
12. What the service center may check
- Retrieve and review all DTCs, including whether multiple LOC DTCs are stored.
- Evaluate battery health.
- Evaluate system voltage.
- Inspect or diagnose the TCM according to the applicable Jeep service procedure; detailed steps are not included in the supplied evidence.
13. Possible repair or resolution
- Not yet established by verified evidence. The supplied communication provides diagnostic direction but does not provide a verified repair outcome in the available excerpt.
14. Affected vehicles
- Jeep Grand Cherokee · 2024–2026 · US
- Jeep Wagoneer · 2024–2026 · US
15. Related TSBs / service bulletins
- NHTSA Manufacturer Communication 11021842; Jeep service communication 9100641; published August 5, 2025. It lists U0129 among relevant codes in a multiple-LOC-DTC diagnostic procedure and directs checks of battery health, system voltage, and the TCM when multiple LOC DTCs are present.
16. Recall information
No recall relationship is established by verified evidence.
17. Official manufacturer information
Official source: NHTSA Manufacturer Communication 11021842, Jeep service communication 9100641, published 2025-08-05: https://static.nhtsa.gov/odi/ffdd/tsbs/TSBS_RECEIVED_2025-2026.zip#nhtsa_id=11021842
- NHTSA: NHTSA Manufacturer Communication 11021842: 9100641 · official_tsb
19. Frequently asked questions
What does U0129 mean on an applicable Jeep?
The supplied official evidence lists U0129 as a relevant code in a multiple-LOC-DTC diagnostic context. A complete U0129 definition is not yet established by verified evidence.
What should be checked when U0129 occurs with multiple LOC DTCs?
The official communication directs checks of battery health, system voltage, and the TCM.
Is the ESM the cause if multiple modules report the same LOC?
According to the supplied official communication, no. It states that the ESM is not the cause in that situation because it is not a gateway module.
Which vehicles are covered by the supplied evidence?
2024–2026 Jeep Grand Cherokee and 2024–2026 Jeep Wagoneer vehicles in the United States.
Can the vehicle be driven or charged with U0129?
Not yet established by verified evidence.