U0103

Lost Communication With Gear Shift Control Module A

Communication / transmission Generic OBD-II High

What it means

U0103 sets when a module (usually the ECM/PCM or TCM) stops receiving messages from the gear shift control module, which manages gear selection — critical on shift-by-wire transmissions. The transmission may drop into a failsafe mode, refuse to shift, or misread the selected gear, so the car often becomes hard to drive normally until it's repaired.

High

Can I keep driving? Limited — losing the shift control module can force the transmission into a failsafe (limp) mode or prevent gear selection; drive gently and get it fixed soon.

Real-world scan data

Seen in

354

scans in the past year

Found in

0.1%

of scans

0.1%

of scans that found faults

Appears alongside · share of U0103 scans

U0121in 37.3% of scans

U0100in 36.7% of scans

U0101in 35.3% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Transmission stuck in one gear or in limp/failsafe mode
Gear selector reads wrong or won't select a gear (shift-by-wire)
Check-engine and/or transmission warning light on
Harsh, delayed, or no shifting
No-crank or no-start on some shift-by-wire systems if Park/Neutral can't be confirmed

Common causes

Most likely first

Damaged wiring or connector at the gear shift control moduleLikely
Loss of power or ground to the shift moduleCommon
CAN bus wiring fault between the shift module and the ECM/TCMCommon
Failed gear shift control moduleLess often
Corrosion or water intrusion at the shifter/module connectorLess often

How to diagnose & fix

Work through it in order

Scan all modules and check whether the shift module responds at all.
Inspect the shift module's connector, power, and ground for damage or corrosion.
Check the CAN bus wiring between the shift module and the ECM/TCM for opens or shorts.
Verify the module has proper power and ground with a meter.
If wiring and power are good, the gear shift control module likely needs replacement and programming. Clear and re-test.

FAQ

Quick answers

Is it safe to drive with U0103?+

Not really — a transmission that drops into limp mode or can't confirm gear position is unpredictable. Drive only as far as needed to get it repaired.

Can I just clear U0103?+

It'll clear but returns immediately if the module is still offline. This one needs the wiring or module fixed.

Read & clear U0103 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX