U0101 — Lost Communication With TCM

U0101 means the transmission control module dropped off the CAN network. Expect limp mode. Check TCM power, grounds and bus wiring before replacing the module.

Cost range: $100–$2,000. Severity: high. Safe to drive? No. The transmission will default to limp mode and may not shift.

Most common causes of U0101

1. TCM power or ground fault — Blown fuse is the cheapest cause. ($20–$200)
2. CAN bus wiring damage — Rodent damage and chafing are common. ($150–$600)
3. Fluid intrusion into the TCM connector — ATF wicks up the harness into the module. ($300–$1,200)
4. Failed TCM — Needs programming after replacement. ($700–$2,000)

Symptoms drivers report with U0101

• Limp mode
• Transmission won't shift
• Multiple warning lights
• Speedometer issues