THE CODE DIRECTORY
Diagnostic code references — Page 116.
Browse canonical reference entries. Each definition keeps its own source and vehicle-applicability limits.
Generic OBD-II
U0631
Lost Communication With Engine Coolant Temperature Sensor 5
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Generic OBD-II
U0632
Lost Communication With Fan 1
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Generic OBD-II
U0633
Lost Communication With Fan 2
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Generic OBD-II
U0634
Lost Communication With Hybrid/EV Battery Pack Coolant Temperature Sensor A
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Generic OBD-II
U0635
Lost Communication With Hybrid/EV Battery Pack Coolant Temperature Sensor B
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Generic OBD-II
U0636
Lost Communication With Hybrid/EV Battery Pack Coolant Control Valve A
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Generic OBD-II
U0637
Lost Communication With Hybrid/EV Battery Pack Coolant Control Valve B
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Generic OBD-II
U0638
Lost Communication With Hybrid/EV Electronics Coolant Temperature Sensor A
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Generic OBD-II
U0639
Lost Communication With Hybrid/EV Electronics Coolant Temperature Sensor B
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Generic OBD-II
U063A
Lost Communication With Hybrid/EV Electronics Coolant Temperature Sensor C
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Generic OBD-II
U063B
Lost Communication With Coolant Bypass Valve Actuator A
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Generic OBD-II
U063C
Lost Communication With Coolant Bypass Valve Actuator B
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Generic OBD-II
U063D
Lost Communication With Hybrid/EV Electronics Coolant Pump A
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Generic OBD-II
U063E
Lost Communication With Exhaust Heat Exchanger Bypass Valve Actuator A
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Generic OBD-II
U063F
Lost Communication With Engine Coolant Flow Control Valve Position Sensor
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Generic OBD-II
U0640
Lost Communication With EVAP Fuel Vapor Temperature Sensor Circuit
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Generic OBD-II
U0641
Lost Communication With EVAP System Pressure Sensor/Switch Circuit A
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Generic OBD-II
U0642
Lost Communication With EVAP System Pressure Sensor/Switch Circuit B
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Generic OBD-II
U0643
Lost Communication With Turbocharger/Supercharger A Temperature Sensor
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Generic OBD-II
U0644
Lost Communication With Wastegate Position Sensor A
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Generic OBD-II
U0645
Lost Communication With Active Air Dam Module
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Generic OBD-II
U0646
Lost Communication With Motor Electronics Coolant Pump A
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Generic OBD-II
U0647
Lost Communication With Motor Electronics Coolant Pump B
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Generic OBD-II
U0648
Lost Communication With Motor Electronics Coolant Pump C
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Generic OBD-II
U0649
Lost Communication With Coolant Pump D
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Generic OBD-II
U064A
Lost Communication With Hybrid/EV Battery Pack Current Sensor A
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Generic OBD-II
U064B
Lost Communication With Hybrid/EV Battery Pack Current Sensor B
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Generic OBD-II
U064C
Lost Communication With Hybrid/EV Battery Pack Current Sensor C
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Generic OBD-II
U064D
Lost Communication With Trailer Brake Control Switch
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Generic OBD-II
U064E
Lost Communication With EGR Cooler Bypass Position Sensor Bank 1
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Generic OBD-II
U064F
Lost Communication With Intake Manifold Runner Position Sensor Bank 1
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Generic OBD-II
U0650
Lost Communication With Exhaust Pressure Control Valve A Sensor/Switch
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Generic OBD-II
U0651
Lost Communication With EGR Sensor A
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Generic OBD-II
U0652
Lost Communication With EGR Sensor B
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Generic OBD-II
U0653
Lost Communication With EGR Sensor C
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Generic OBD-II
U0654
Lost Communication With Diesel Intake Air Flow A Position Sensor
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Generic OBD-II
U0655
Lost Communication With Diesel Intake Air Flow B Position Sensor
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Generic OBD-II
U0656
Lost Communication With Turbocharger/Supercharger Boost Control A Position Sensor
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Generic OBD-II
U0657
Lost Communication With Turbocharger/Supercharger Bypass Valve A Position Sensor
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Generic OBD-II
U0658
Lost Communication With Windshield Temperature Sensor
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Generic OBD-II
U0659
Lost Communication With Left Front Temperature Actuator
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Generic OBD-II
U065A
Lost Communication With Right Front Temperature Actuator
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Generic OBD-II
U065B
Lost Communication With Left Front Mode Actuator
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Generic OBD-II
U065C
Lost Communication With Right Front Mode Actuator
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Generic OBD-II
U065D
Lost Communication With Air Intake Actuator
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Generic OBD-II
U065E
Lost Communication With Ram Air Actuator
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Generic OBD-II
U065F
Lost Communication With Left Rear Temperature Actuator A
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Generic OBD-II
U0660
Lost Communication With Left Rear Temperature Actuator B
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Generic OBD-II
U0661
Lost Communication With Right Rear Temperature Actuator A
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Generic OBD-II
U0662
Lost Communication With Right Rear Temperature Actuator B
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Generic OBD-II
U0663
Lost Communication With Rear Mode Actuator
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Generic OBD-II
U0664
Lost Communication With Rear HVAC Air Cutoff Actuator
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Generic OBD-II
U0665
Lost Communication With Fuel Rail Pressure Sensor Bank 2
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Generic OBD-II
U0666
Lost Communication With Reductant Pressure Sensor
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Generic OBD-II
U0667
Lost Communication With Engine Oil Temperature Sensor A
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Generic OBD-II
U0668
Lost Communication With Engine Oil Level Sensor Circuit
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Generic OBD-II
U0669
Lost Communication With EGR Sensor D
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Generic OBD-II
U066A
Lost Communication With EGR Sensor E
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Generic OBD-II
U066B
Lost Communication With Turbocharger/Supercharger Bypass Valve B Position Sensor
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Generic OBD-II
U066C
Lost Communication With Exhaust Heat Exchanger Bypass Valve Actuator B
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Generic OBD-II
U066D
Lost Communication With Charge Air Cooler Temperature Sensor Bank 1
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Generic OBD-II
U066E
Lost Communication With Charge Air Cooler Temperature Sensor Bank 2
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Generic OBD-II
U066F
Lost Communication With Low Pressure Fuel System Sensor
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Generic OBD-II
U0670
Lost Communication With Fuel Temperature Sensor A
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Generic OBD-II
U0671
Lost Communication With Fuel Temperature Sensor B
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Generic OBD-II
U0672
Lost Communication With Engine Coolant Pump
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Generic OBD-II
U0673
Lost Communication With Ion Sense Module
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Generic OBD-II
U0674
Lost Communication With Wastegate Position Sensor B
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Generic OBD-II
U0675
Lost Communication With Turbocharger/Supercharger Speed Sensor A
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Generic OBD-II
U0676
Lost Communication With Fuel Level Sensor A
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Generic OBD-II
U0677
Lost Communication With Fuel Level Sensor B
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Generic OBD-II
U0678
Lost Communication With Fuel Level Sensor C
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Generic OBD-II
U0679
Lost Communication With Transmission Fluid Pressure Sensor/Switch A
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Generic OBD-II
U067A
Lost Communication With Transmission Fluid Pressure Sensor/Switch B
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Generic OBD-II
U067B
Lost Communication With Engine Disconnect Clutch Pressure Sensor
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Generic OBD-II
U067C
Lost Communication With Fan 3
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Generic OBD-II
U067D
Lost Communication With Fan 4
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Generic OBD-II
U067E
Lost Communication With Exhaust Pressure Control Valve B Sensor/Switch
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Generic OBD-II
U067F
Lost Communication With Barometric Pressure Sensor A
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Generic OBD-II
U0680
Lost Communication With Barometric Pressure Sensor B
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Generic OBD-II
U0681
Lost Communication With Throttle/Pedal Position Sensor/Switch D
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Generic OBD-II
U0682
Lost Communication With Throttle/Pedal Position Sensor/Switch E
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Generic OBD-II
U0683
Lost Communication With Throttle/Pedal Position Sensor/Switch F
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Generic OBD-II
U0684
Lost Communication With Catalyst Temperature Bank 1 Sensor 1
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Generic OBD-II
U0685
Lost Communication With Catalyst Temperature Bank 1 Sensor 2
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Generic OBD-II
U0686
Lost Communication With Catalyst Temperature Bank 2 Sensor 1
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Generic OBD-II
U0687
Lost Communication With Catalyst Temperature Bank 2 Sensor 2
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Generic OBD-II
U0688
Lost Communication With Throttle Position Sensor/Switch G
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Generic OBD-II
U0689
Lost Communication With Turbocharger/Supercharger B Temperature Sensor
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Generic OBD-II
U068A
Lost Communication With Barometric Pressure Sensor C
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Generic OBD-II
U068B
Lost Communication With Turbocharger/Supercharger Inlet Pressure Sensor A
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Generic OBD-II
U068C
Lost Communication With Turbocharger/Supercharger Inlet Pressure Sensor B
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Generic OBD-II
U068D
Lost Communication With EGR Temperature Sensor A
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Generic OBD-II
U068E
Lost Communication With EGR Temperature Sensor B
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Generic OBD-II
U068F
Lost Communication With EGR Temperature Sensor C
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Generic OBD-II
U0690
Lost Communication With EGR Temperature Sensor D
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Generic OBD-II
U0691
Lost Communication With Exhaust Pressure Sensor A
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Generic OBD-II
U0692
Lost Communication With Exhaust Pressure Sensor B
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Generic OBD-II
U0693
Lost Communication With Humidity Sensor
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Generic OBD-II
U0694
Lost Communication With Hybrid/EV Battery Pack Coolant Pump A
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These are code references, not a list of confirmed faults on every vehicle. Read the source and applicability notes, then match the exact vehicle, year, engine and scan report.