U01B8 — Lost Communication With Switch Input Module “B”

What Does U01B8 Mean?

U01B8 is a diagnostic trouble code indicating: Lost Communication With Switch Input Module “B”. 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 U01B8

⚠️ Check Engine Light (MIL) illuminated
⚠️ No communication with Switch Input Module “B”
⚠️ 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 Switch Input Module “B”
🔍 Power or ground supply issue to Switch Input Module “B”
🔍 Switch Input Module “B” internal failure
🔍 Water intrusion damaging module or connectors
🔍 CAN bus termination resistor fault

Frequently Asked Questions

What does U01B8 mean?

U01B8 indicates: Lost Communication With Switch Input Module “B”. The vehicle's computer has detected that the Switch Input Module “B” is not operating within its expected parameters and stored this diagnostic trouble code.

Can I drive with code U01B8?

You can drive short distances for essential trips, but schedule a diagnosis soon. Driving with U01B8 for extended periods may cause additional problems.

How much does it cost to fix U01B8?

Repair costs for U01B8 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 Switch Input Module “B” for damage
🔧 Check power and ground supply to Switch Input Module “B”
🔧 Replace failed Switch Input Module “B”

1
Find your vehicle above
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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.

U01B8: Lost Communication With Switch Input Module “B”