U0403

Invalid Data Received From Transfer Case Control Module

Network / communication Generic OBD-II Medium

What it means

U0403 means a module is receiving data from the transfer case control module that is out of range or implausible. This mostly affects four-wheel-drive: mode and range selection may be disabled or behave erratically. Normal on-road driving is usually fine, but don't rely on 4WD until the module's wiring, sensors, or software are checked.

Medium

Can I keep driving? Usually yes in normal 2WD/AWD road use, but 4WD range/mode selection may be disabled or unreliable — don't rely on it off-road until fixed.

Common symptoms

What you'll notice

4WD/AWD warning light or 'service 4WD' message on
Unable to shift into or out of 4WD high/low
Erratic or unavailable transfer-case mode selection
Other modules storing 'lost communication' or 'invalid data' codes for the transfer case module

Common causes

Most likely first

Transfer case control module broadcasting out-of-range or implausible values onto the busLikely
Internal transfer case module fault or corrupted softwareCommon
Wiring, connector, or ground fault at the module corrupting bus dataCommon
Transfer-case position/mode sensor feeding impossible readingsLess often

How to diagnose & fix

Work through it in order

Scan all modules and record every stored code, including companion communication codes.
Check transfer case module power, grounds, and connectors.
Inspect the module and transfer-case harness wiring for damage or corrosion.
Verify module software; reflash or replace and program if internally failed, then clear and re-test.

FAQ

Quick answers

Is it safe to drive with U0403?+

For normal on-road driving, usually yes. But four-wheel-drive engagement may be disabled or unreliable, so don't count on 4WD in snow or off-road until it's repaired.

Can I just clear U0403?+

It returns until the fault is fixed. The transfer case module is still sending invalid data, so the wiring, sensor, or module issue must be addressed.

Related codes

Often seen with U0403

U0102Lost Communication With Transfer Case Cont U0114Lost Communication With Four-Wheel Drive C U0404Invalid Data Received From Gear Shift Cont U0401Invalid Data Received From ECM/PCM A

Read & clear U0403 yourself

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

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