What Does U040C Mean?
The ECM is receiving invalid or corrupted data from EGR Control Module B (secondary EGR circuit on vehicles with dual EGR systems). Network communication with the second EGR controller is compromised.
Common Causes
35%
Faulty EGR control module B with internal failure
25%
Damaged wiring or connectors between EGR module B and vehicle network
20%
Secondary EGR position sensor failure or valve assembly fault
15%
CAN bus communication fault affecting secondary modules
5%
Module identification or software configuration error
Diagnostic Steps
1
Step 1: Monitor EGR valve B position and command data with scan tool to identify data anomalies
2
Step 2: Inspect secondary EGR module connectors and wiring for damage, corrosion, or shorts
3
Step 3: Verify power and ground circuits to EGR control module B with multimeter
4
Step 4: Test secondary EGR valve operation and position sensor feedback manually if possible
5
Step 5: Compare data from both EGR modules A and B to isolate communication issue
Estimated Repair Cost
$200 - $900
Parts + labor, varies by vehicle and location
The ECM is receiving invalid or corrupted data from EGR Control Module B (secondary EGR circuit on vehicles with dual EGR systems). Network communication with the second EGR controller is compromised.
The most common cause of U040C (Invalid Data Received From Exhaust Gas Recirculation Control Module "B") is: Faulty EGR control module B with internal failure
Typical repair costs for U040C range from $200 to $900, depending on the vehicle, location, and whether you do it yourself or go to a shop.
May cause increased emissions and reduced fuel economy. Vehicle remains drivable but emissions system effectiveness is compromised.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to U040C 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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