U0100 — Lost Communication with ECM/PCM (GWM Context)
Written and edited by Ethan Cole, Editor-in-Chief · ✓ Technically reviewed by Daniel Wei Chen — Senior Chinese Automotive Diagnostics & Repair Specialist, Sydney · 22 August 2026.
Standard meaning: a module stopped hearing the engine/powertrain computer on the CAN network. U-codes frighten owners because they sound like brain damage; usually they’re wiring, grounds, or a low 12V. On 2025 GWM hybrids, there’s a documented cause with a free fix: recall campaign 8825BC9.
The recall trap. REC-006516 (Dec 2025, Tank 500 HEV/PHEV, Tank 300 HEV, Cannon Alpha PHEV): an ungrounded shielding ring in the high-voltage harness weakens electromagnetic shielding — the regulator’s own wording is “abnormal communications between the engine and transmission control systems”, with warning lights, reduced torque and weakened hybrid cooling. That is a U-code presentation. On any 2025 build, check the VIN on our recalls tracker before paying for diagnosis — an owner (or workshop) can chase phantom modules for weeks when the answer is a recall appointment.
What it means on your GWM
| Situation | Likely story | First move |
|---|---|---|
| 2025 hybrid (Tank/Cannon Alpha) | The recalled shielding defect until proven otherwise. | VIN check; recall visit if open. |
| Any model, after jump-start or battery work | Low/unstable 12V during the event confused the network. | 12V health first; many U-codes never return. |
| Recurring, recall done or N/A | Genuine harness/connector/ground fault. | Workshop CAN diagnosis — this is not a DIY hunt. |
Safe owner checks
- Recall status (free, two minutes, from your couch).
- 12V battery health and terminals.
- Note exactly which warnings appeared together and when — that cluster is the workshop’s map.
When it’s a workshop job
Anything recurring. CAN faults need a scope and a wiring diagram, and on hybrids parts of the loom live near orange cables — never open or probe high-voltage components or connectors yourself. That line isn’t ours to move.
Code definition per SAE J2012. Recall linkage: official Australian recall register REC-006516 defect description — the connection between its wording and U-code symptoms is stated there, not inferred by us.
Disclaimer: Information on this page is general guidance only and does not replace the manufacturer’s official documentation or the judgement of a qualified technician. Never open, touch or work on any orange high-voltage component. Fault-code behaviour varies between markets, model years and software versions. Last verified: 22 August 2026.