U0101 — Lost Communication with TCM
Category: Network / Communication Severity: Medium
Updated:
DTC code U0101 means: Lost Communication with TCM. It falls under the "Network / Communication" category, with an estimated severity of Medium. Common causes include cAN bus wiring issue, faulty TCM and poor ground/connection; it's worth confirming the diagnosis before replacing parts.
Possible causes
- CAN bus wiring issue
- Faulty TCM
- Poor ground/connection
- Low battery voltage
Symptoms
- Several warning lights on at once
- Communication faults between modules
How to diagnose it step by step
- Check battery and grounds.
- Check TCM fuses.
- Check the TCM connector (inside the transmission on some cars).
- Measure the CAN bus.
- Replace or reprogram the TCM.
How to fix it
Check the CAN wiring and grounds; it may be a control unit.
Estimated repair cost
From $0 to $400–1,300 (TCM).
Frequently asked questions
What does DTC code U0101 mean?
Lost Communication with TCM.
Is code U0101 serious?
Severity Medium. Not urgent, but worth diagnosing to avoid bigger damage.
Can I keep driving with code U0101?
Carefully; the transmission may stay in limp mode.
Related codes
U0100 U0121 U0140 U0151 U0155 U0164
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