A loose, corroded, or damaged connector at the gear shift module or at the module it communicates through; A chafed, pinched, or open wire in the CAN bus or power/ground circuit serving the gear shift module; A failed gear shift module, often from internal electronics or a faulty position sensor inside the assembly; A blown fuse or poor ground that removes power from the gear shift module; A network fault such as a shorted CAN line or a failed terminating resistor that disrupts communication for several modules; A software or configuration mismatch after battery replacement, module replacement, or a low-voltage event; A failing battery or charging system that drops voltage low enough to take the module offline intermittently

DTC codes / U01xx · Lost communication with a control module / U0103

U0103Lost Communication With Gear Shift Module

Q: What does code U0103 mean?

Lost Communication With Gear Shift Module. U0103 means the engine control module or another network module has lost the controller area network (CAN) communication link with the gear shift module, which is the electronic shifter assembly that reports lever position and range commands. The computer detected that no valid messages arrived from the gear shift module within the expected time window, so it flagged the module as offline.

U0103 means the engine control module or another network module has lost the controller area network (CAN) communication link with the gear shift module, which is the electronic shifter assembly that reports lever position and range commands. The computer detected that no valid messages arrived from the gear shift module within the expected time window, so it flagged the module as offline.

SystemNetwork

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaLost communication with a control module

Symptoms you may notice

A steady or intermittent check engine light, often with no other symptoms besides the warning light
The transmission may default to a limp or fixed gear, or refuse to shift out of park
The instrument cluster may not display the selected gear or may show a flashing or blank range indicator
Remote start, keyless start, or push-button start may be disabled because the module cannot confirm park or neutral
The vehicle may fail to crank or may start only after several attempts
Other modules on the same network may log communication codes, and multiple warning lights can appear at once

Common causes, most likely first

A loose, corroded, or damaged connector at the gear shift module or at the module it communicates through
A chafed, pinched, or open wire in the CAN bus or power/ground circuit serving the gear shift module
A failed gear shift module, often from internal electronics or a faulty position sensor inside the assembly
A blown fuse or poor ground that removes power from the gear shift module
A network fault such as a shorted CAN line or a failed terminating resistor that disrupts communication for several modules
A software or configuration mismatch after battery replacement, module replacement, or a low-voltage event
A failing battery or charging system that drops voltage low enough to take the module offline intermittently

How to diagnose and fix it

Scan all modules for stored and pending codes, record freeze-frame data, and note whether U0103 is current or history
Inspect the gear shift module connector and nearby harness for corrosion, backed-out pins, and chafing, then clean and reseat it
Check the fuse and ground serving the gear shift module, and load-test the battery and charging system
Measure CAN bus voltage and resistance at the diagnostic connector and at the module to confirm whether the bus is intact
Perform a wiggle test on the harness while watching live module communication status to catch an intermittent open circuit
If power, ground, and bus integrity are confirmed, substitute a known-good gear shift module or perform the manufacturer's relearn and configuration procedure
Clear codes, road-test through all gear ranges, and verify the module stays online across several key cycles

What a U0103 often really means

A dead battery or a jump-start gone wrong is a common trigger, because the gear shift module can drop offline during a low-voltage event and set U0103 without any hardware failure.
The code names the gear shift module, but the real fault is frequently a shared CAN bus problem or a power/ground issue that also affects other modules, so chasing the shifter alone can miss the cause.
On vehicles with a rotary or joystick-style shifter, the module may be a separate electronic unit under the console rather than the lever itself, and technicians sometimes replace the lever when the module is the failed part.
U0103 can appear after module replacement or reprogramming when the new module has not been configured or the network has not been re-learned, so a relearn may clear it without any parts.
Intermittent U0103 that returns only in damp weather or over rough roads points to a harness chafe or connector issue rather than a failed module, and a wiggle test usually finds it faster than parts swapping.

Can I keep driving with U0103?

The vehicle may still drive, but a lost gear shift module can leave the transmission in limp mode or prevent shifting out of park, so avoid highway driving and long trips until the fault is diagnosed. If the shifter will not engage a gear or the car will not start reliably, stop driving and have it towed.

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.