What Does U040B Mean?
The ECM is receiving invalid or corrupted data from EGR Control Module A over the vehicle communication network. This affects emissions system monitoring and EGR valve operation feedback.
Common Causes
35%
Faulty EGR control module with internal circuit or processor failure
25%
Damaged wiring or corroded connectors between EGR module and network
20%
EGR position sensor failure sending implausible data to control module
15%
CAN bus network fault or termination resistance issue
5%
Software corruption or module programming error
Diagnostic Steps
1
Step 1: Monitor EGR valve position and commanded position data with scan tool during operation
2
Step 2: Inspect EGR control module and valve assembly connectors for corrosion or damage
3
Step 3: Check power supply and ground circuits to EGR control module with multimeter
4
Step 4: Test EGR position sensor operation and verify valve moves smoothly without carbon buildup
5
Step 5: Check CAN bus network integrity and verify proper termination resistance
Estimated Repair Cost
$200 - $850
Parts + labor, varies by vehicle and location
The ECM is receiving invalid or corrupted data from EGR Control Module A over the vehicle communication network. This affects emissions system monitoring and EGR valve operation feedback.
The most common cause of U040B (Invalid Data Received From Exhaust Gas Recirculation Control Module "A") is: Faulty EGR control module with internal circuit or processor failure
Typical repair costs for U040B range from $200 to $850, depending on the vehicle, location, and whether you do it yourself or go to a shop.
May cause increased emissions, check engine light, and potential emissions test failure. Vehicle remains drivable but may experience reduced performance.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to U040B to identify the root cause.
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Quick Info
Category
Network
System
Emissions/EGR System
Difficulty
Type
Generic (SAE)
Recommended Tools
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