What Does U0291 Mean?
The vehicle's network has lost communication with gear shift control module 'B'. This typically indicates a secondary shift control system, found in vehicles with electronic shift-by-wire systems or dual-range transfer cases.
Common Causes
35%
Failed gear shift control module B
30%
Damaged wiring harness or connector to shift module B
20%
CAN bus communication network fault
10%
Poor ground connection at shift module B
5%
Loss of power supply to module B
Diagnostic Steps
1
Step 1: Verify power and ground supply to gear shift control module B using multimeter
2
Step 2: Inspect wiring harness and connectors for damage, corrosion, or disconnection
3
Step 3: Test CAN bus communication signals at module B connector using scan tool diagnostics
4
Step 4: Check for related transmission or shift system codes that may indicate root cause
5
Step 5: Replace gear shift control module B if all electrical and network tests confirm proper operation
Estimated Repair Cost
$300 - $900
Parts + labor, varies by vehicle and location
The vehicle's network has lost communication with gear shift control module 'B'. This typically indicates a secondary shift control system, found in vehicles with electronic shift-by-wire systems or dual-range transfer cases.
The most common cause of U0291 (Lost Communication With Gear Shift Control Module "B") is: Failed gear shift control module B
Typical repair costs for U0291 range from $300 to $900, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle may be stuck in one gear or fail to shift properly. Avoid driving until repaired to prevent being stranded or experiencing sudden gear changes.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to U0291 to identify the root cause.
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Quick Info
Category
Network
System
Transmission Control System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
