U0101: Lost Communication With TCM
What Does U0101 Mean?
U0101 is a diagnostic trouble code indicating: Lost Communication With TCM. This code relates to the network communication system. It has been reported in NHTSA complaints across 18 different vehicle models.
Symptoms of U0101
- ⚠️ Check engine light illuminated
- ⚠️ Engine stalling or dying
- ⚠️ Loss of engine power
- ⚠️ Jerking or surging while driving
- ⚠️ Traction control system activated
- ⚠️ Vehicle enters limp/reduced power mode
Common Causes
- 🔍 Failed ignition coil
- 🔍 Throttle body or throttle position sensor issue
- 🔍 Wiring or connector problem
- 🔍 Sensor or control module malfunction
U0101 Reports by Year
Real Owner Reports
From NHTSA complaint database — actual owner descriptions.
"*ONGOING *PLEASE SEE ORIGINAL COMPLAINT # 10473215 *CLUTCH REPLACED TWICE AND TRANS REPROGRAMMED 4/5 TIMES (WITHIN 35, 000) *NOW CAR NOT STARTING- 4 TIMES IN 2 MONTHS. SYMPTOMS ON 1/3/2015- 4TH TIME: DASH LIGHTS UP, RADIO AND HEATER WORK, HEADLIGHTS- NO, BUT OTHER LIGHTS- YES, NO CRANK WHEN TRYING T"
— Ford Focus owner, 01/03/2015
"ENGINE STALLED AND SHUTDOWN WHILE DRIVING WITH LOSS OF CONTROL. ENGINE ALSO REV'ED UP DOWN WITHOUT ACCELERATION AND DECELERATION WHILE DRIVING AND TRACTION WARNING CONTROL LIGHT CAME ON. CAR WAS DRIVEN TO NEARBY PARKING LOT WHERE IT COMPLETELY SHUTDOWN. CAR NEEDED TO BE TOWED TO DEALER, AS IT COULD "
— Ford Focus owner, 10/18/2014
"FORD TRANSMISSION PROBLEMS WONT GO AWAY!! TRANSMISSION SHUTTER AND POOR INITIAL ACCELERATION. THE CLUTCH HAS BEEN REPLACED TWICE AND TCM TWICE BY FORD DEALER. AFTER THE LAST TCM REPLACEMENT IN 2016 PROBLEMS CONTINUED AND I WAS TURNED AWAY BY FORD DEALERSHIPS BECAUSE NO ENGINE LIGHT CAME ON. NOW THA"
— Ford Focus owner, 12/26/2020
Source: NHTSA Complaints Database
Most Reported Vehicles for U0101
Based on NHTSA owner complaint data.
| # | Vehicle | Reports |
|---|---|---|
| 1 | FORD FOCUS | |
| 2 | CHEVROLET IMPALA | |
| 3 | CHEVROLET EQUINOX | |
| 4 | CHEVROLET COLORADO | |
| 5 | DODGE CHARGER | |
| 6 | DODGE DART | |
| 7 | FORD EXPLORER | |
| 8 | CHEVROLET MALIBU | |
| 9 | CHEVROLET TAHOE | |
| 10 | CHEVROLET SUBURBAN | |
| 11 | NISSAN SENTRA | |
| 12 | NISSAN FRONTIER | |
| 13 | HYUNDAI ELANTRA | |
| 14 | KIA SOUL | |
| 15 | DODGE DURANGO |
U0101 Reports by Vehicle
Detailed NHTSA complaint analysis for each vehicle model.
Diagnostic Tips
- Scan all modules, save freeze-frame data, and clear unrelated history codes before focusing on U0101.
- Confirm whether companion codes are present first; they often identify the root cause sooner than the headline DTC.
- Prioritize inspection around power train and the most common failure path for this code family.
- Perform a voltage-drop and continuity check on the affected circuit and verify 5V reference/ground stability under load.
- After each repair step, complete one drive cycle and verify readiness monitors instead of judging success after a quick idle test.
- If the code keeps returning on high-incidence platforms (for example FORD FOCUS), check TSB patterns and wiring/connector fitment before major part replacement.
Common Mistakes to Avoid
- ❌ Skipping freeze-frame review and losing the exact RPM/load conditions when the fault set.
- ❌ Replacing modules before checking grounds, voltage drop, and harness rub-through near heat/vibration points.
- ❌ Clearing U0101 and returning the car before monitors complete — this often creates repeat visits.
- ❌ Treating intermittent wiring or connector faults as permanent component failure without wiggle testing.
Frequently Asked Questions
What causes communication codes?
Can a bad battery cause network codes?
What To Do Next
Possible Fixes
- 🔧 Have the code scanned with a professional-grade scanner to read freeze frame data
- 🔧 Test the relevant sensor(s) with a multimeter before replacing
- 🔧 Inspect wiring harness and connectors for damage, corrosion, or loose connections
- 🔧 Check battery voltage and ground connections; inspect CAN bus wiring
- 🔧 If DIY repair isn't feasible, get a diagnostic from a trusted mechanic ($50-150)
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Find your vehicle above
Click your make and model for real owner reports and common causes specific to your vehicle.
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Check for recalls
Go to nhtsa.gov/recalls and enter your VIN. Free repairs if covered.
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Get a professional diagnosis
A code alone doesn't identify the exact failed part. A diagnostic ($50–$150) pinpoints the root cause.