U0120 — Lost Communication With Starter / Generator Control Module

What Does U0120 Mean?

U0120 is a diagnostic trouble code indicating: Lost Communication With Starter / Generator Control Module. This code relates to the network communication system. The vehicle's computer detected a condition outside normal operating parameters and stored this code.

Symptoms of U0120

⚠️ Check Engine Light (MIL) illuminated
⚠️ No communication with Starter / Generator Control Module
⚠️ Multiple warning lights may illuminate simultaneously
⚠️ Related system completely inoperative
⚠️ Multiple warning lights on dashboard

Common Causes

🔍 CAN bus wiring fault (open or shorted) to Starter / Generator Control Module
🔍 Power or ground supply issue to Starter / Generator Control Module
🔍 Starter / Generator Control Module internal failure
🔍 Water intrusion damaging module or connectors
🔍 CAN bus termination resistor fault

Frequently Asked Questions

What does U0120 mean?

U0120 indicates: Lost Communication With Starter / Generator Control Module. The vehicle's computer has detected that the Starter / Generator Control Module is not operating within its expected parameters and stored this diagnostic trouble code.

Can I drive with code U0120?

You can drive short distances for essential trips, but schedule a diagnosis soon. Driving with U0120 for extended periods may cause additional problems.

How much does it cost to fix U0120?

Repair costs for U0120 typically range from $80 to $1200, 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 CAN bus wiring to Starter / Generator Control Module for damage
🔧 Check power and ground supply to Starter / Generator Control Module
🔧 Replace failed Starter / Generator Control Module

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.

U0120: Lost Communication With Starter / Generator Control Module