A failed park lock/pawl control module or its internal power supply.; Corroded, loose, or damaged wiring or connectors at the park lock module or along the CAN bus.; A blown fuse or poor ground connection supplying the park lock module.; CAN bus wiring faults such as an open circuit, short to ground, or short to voltage on the CAN high or CAN low lines.; A faulty detecting module that is not properly receiving or interpreting messages from the park lock module.; Low battery voltage or charging system issues causing modules to drop offline intermittently.; Aftermarket accessories or improper electrical repairs that disturb the CAN bus or module power.

DTC codes / U01xx · Lost communication with a control module / U01BA

U01BALost Communication With Park Lock/Pawl Control Module

Q: What does code U01BA mean?

Lost Communication With Park Lock/Pawl Control Module. U01BA is a generic communication fault that sets when a control module on the vehicle's Controller Area Network (CAN) bus reports it has lost all messages from the park lock/pawl control module. The detecting module, often the body control module or transmission control module, expects periodic status frames from the park lock/pawl module and flags this code after a timeout period with no valid data.

U01BA is a generic communication fault that sets when a control module on the vehicle's Controller Area Network (CAN) bus reports it has lost all messages from the park lock/pawl control module. The detecting module, often the body control module or transmission control module, expects periodic status frames from the park lock/pawl module and flags this code after a timeout period with no valid data.

SystemNetwork

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaLost communication with a control module

Symptoms you may notice

The gear selector may not move out of Park, or may move without the brake pedal being applied.
A warning light or message on the dash indicating a transmission or park system fault.
The vehicle may fail to start because the park lock module is not confirming Park position.
In some vehicles, the shifter may feel loose or allow movement without the ignition on.
Often no symptoms besides the warning light, especially if the park lock function is mechanically redundant.
Intermittent operation of the park lock solenoid, working on some key cycles but not others.

Common causes, most likely first

A failed park lock/pawl control module or its internal power supply.
Corroded, loose, or damaged wiring or connectors at the park lock module or along the CAN bus.
A blown fuse or poor ground connection supplying the park lock module.
CAN bus wiring faults such as an open circuit, short to ground, or short to voltage on the CAN high or CAN low lines.
A faulty detecting module that is not properly receiving or interpreting messages from the park lock module.
Low battery voltage or charging system issues causing modules to drop offline intermittently.
Aftermarket accessories or improper electrical repairs that disturb the CAN bus or module power.

How to diagnose and fix it

Verify battery voltage and charging system output, as low voltage is a common cause of communication codes.
Check all fuses and grounds related to the park lock/pawl control module and the detecting module.
Inspect the park lock module connectors and wiring for corrosion, chafing, or loose pins.
Use a scan tool to check for other communication codes and confirm which modules are online.
Perform a CAN bus voltage and resistance test to rule out bus wiring faults.
If wiring and power are good, substitute a known-good park lock module or perform a module swap to confirm the fault.
After repair, clear codes and verify communication is restored and the park lock function operates correctly.

Park lock module communication traps

A park lock/pawl control module that is completely dead will often set U01BA alongside U0100 or U0140, so check for multiple communication codes before condemning the module.
The park lock function is sometimes integrated into the shifter assembly or the body control module, so the 'module' may not be a separate serviceable box.
Intermittent U01BA codes are frequently caused by a weak battery or a failing ground connection rather than the module itself.
A scan tool that can read live data from the park lock module will show whether the module is powered and communicating, which saves unnecessary parts replacement.
Do not overlook aftermarket remote starters or alarm systems that tap into the CAN bus and can disrupt park lock messages.

Can I keep driving with U01BA?

If the vehicle starts and moves normally, you can drive to a repair shop, but avoid relying on the park lock function and use the parking brake every time you park. If the vehicle will not shift out of Park or will not start, do not force the shifter; have it towed to avoid damage.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.