Network & communication
Definition only
Lights the check engine lamp
U01B7: Lost Communication With Switch Input Module A
Standardized SAE J2012 code · U01xx — Lost communication with modules
What does U01B7 mean?
ECU lost communication with switch input module A (collects switch signals — windows, lights, etc.).
The code tells you which monitor failed, not which part is broken. Test before replacing parts.
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
Common causes
- High Module unpowered
- Low Gateway module routing CAN messages incorrectly
- Low CAN terminating resistor (120 Ω) drifted out of spec
Likelihood is a general estimate across vehicles; your make and model may differ.
Add your car to see reports of U01B7 on the same make and model first.
U01B7 in the community
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