U01B2 code meaning
Lost Communication With Planetary Gear Set Control Module
Network system Generic code U01xx codes Check engine light
What U01B2 means
Hybrid transmissions such as the two-mode system developed by GM, Daimler, Chrysler and BMW use two or three planetary gear sets plus clutches to switch between power-split and fixed-ratio operation. A planetary gear set control module would run those shift elements and report their state to the hybrid or transmission controller. U01B2 means this module has gone off the network, so the controller no longer knows which gear-set state is engaged. No manufacturer documents the code publicly. CARB 1968.2 counts transmission and hybrid control units among the monitored powertrain parts, so a MIL is likely wherever the code is used. Expect a hybrid system warning together with reduced power or a limited fallback mode; U04B3 covers implausible data from the same module.
U01B2 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U01B2
- Hybrid system warning
- Reduced power or limited fallback mode
- MIL on
Common causes of U01B2
- Most likelyDamaged CAN wiring or connector at the transmission
- PossibleModule without supply voltage or ground
- Less likelyPlanetary gear set control module faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Planetary gear moduleCAN bus
What each part of U01B2 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| B2 | The exact fault in that area. |
What to do next
- Note U01B2 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U01B2
What does U01B2 mean?
U01B2 means "Lost Communication With Planetary Gear Set Control Module". Hybrid transmissions such as the two-mode system developed by GM, Daimler, Chrysler and BMW use two or three planetary gear sets plus clutches to switch between power-split and fixed-ratio operation. It is a generic code, so it means the same on every make.
Is it safe to drive with U01B2?
Drive gently and only to a workshop. With U01B2 the car can go into limp mode (reduced power) to protect itself.
Will U01B2 fail an emissions test?
Yes, it can. U01B2 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is U01B2 to fix?
Difficulty: hard. A typical repair takes 1 to 5 hours of work. This is a job for a workshop.
Will U01B2 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.