U3021 — Control Module Wake-up Circuit B Performance

What Does U3021 Mean?

U3021 is a diagnostic trouble code indicating: Control Module Wake-up Circuit B Performance. This code relates to the vehicle systems system. The vehicle's computer detected a condition outside normal operating parameters and stored this code.

Symptoms of U3021

⚠️ Check Engine Light (MIL) illuminated
⚠️ Control Module Wake-up not meeting expected output
⚠️ Degraded performance of related system
⚠️ System warning light illuminated

Common Causes

🔍 Control Module Wake-up degraded from age or contamination
🔍 Mechanical wear in Control Module Wake-up or related parts
🔍 Restriction or blockage affecting Control Module Wake-up
🔍 Calibration drift in Control Module Wake-up

Frequently Asked Questions

What does U3021 mean?

U3021 indicates: Control Module Wake-up Circuit B Performance. The vehicle's computer has detected that the Control Module Wake-up is not operating within its expected parameters and stored this diagnostic trouble code.

Can I drive with code U3021?

You can drive short distances for essential trips, but schedule a diagnosis soon. Driving with U3021 for extended periods may cause additional problems.

How much does it cost to fix U3021?

Repair costs for U3021 typically range from $50 to $400, depending on the root cause. Simple wiring or connector repairs are on the lower end, while component replacement costs more. A proper diagnosis ($80–$150 at most shops) will identify the exact cause before committing to expensive parts.

What To Do Next

Possible Fixes

🔧 Inspect Control Module Wake-up for contamination or wear
🔧 Replace Control Module Wake-up
🔧 Address any related mechanical faults

1
Find your vehicle above
Click your make and model for real owner reports and common causes specific to your vehicle.
2
Check for recalls
Go to nhtsa.gov/recalls and enter your VIN. Free repairs if covered.
3
Get a professional diagnosis
A code alone doesn't identify the exact failed part. A diagnostic ($50–$150) pinpoints the root cause.

U3021: Control Module Wake-up Circuit B Performance