Code
U1702
ALFA ROMEO
U — Network/User
CAN bus communication between DLC and CAN line
Views:
UK: 6
EN: 11
RU: 9
AI status
Completed
Completed
100%
Causes
- Corroded, bent or damaged DLC connector pins
- Open, shorted or high-resistance CAN_H or CAN_L wiring
- Missing or incorrect termination (open/failed 60 Ω total)
- Intermittent connector or ground connection
- Blown fuse or power supply interruption to gateway/module
- Aftermarket device or trailer wiring interfering with CAN bus
Symptoms
- Unable to communicate with one or more modules via a scan tool at the DLC
- Multiple U-codes or module communication DTCs present
- Intermittent or complete loss of functions controlled over the CAN bus (instruments, body control, immobilizer, etc.)
- No response when attempting reprogramming or key programming
- MIL may or may not be illuminated depending on affected modules
What to check
- Read and record all stored and pending DTCs and freeze frame data using a diagnostic tool
- Visually inspect DLC and nearby harness for corrosion, damage, debris or bent pins
- Verify battery voltage and good chassis/engine grounds before testing
- Inspect fuses and relays that feed gateway/CAN modules
- Check for recent aftermarket installs or trailer wiring connected to DLC area
- Scan which modules respond; note any modules that are missing from the bus
Signal parameters
- Recessive (idle) voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (each ~2.5V)
- Dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2.0 V)
- Expected line termination: ≈ 60 Ω measured between CAN_H and CAN_L (two 120 Ω in parallel)
- Common bus speeds: 125 kb/s, 250 kb/s or 500 kb/s depending on bus — confirm vehicle-specific bit rate
Diagnostic algorithm
- Record all network-related DTCs and note which control modules do not respond.
- Visually inspect DLC and CAN wiring for corrosion, damage, water ingress, loose pins or aftermarket splices; repair as required.
- Verify battery voltage (12.4–12.8 V engine off) and good ground connections.
- Check fuses/power supplies feeding gateway and CAN transceivers; restore if blown.
- Measure resistance between CAN_H and CAN_L at the DLC with ignition off — should be ~60 Ω. If open or very high, isolate sections of the bus to find open/short.
- With key on (engine off) measure idle voltages of CAN_H and CAN_L at the DLC — both ~2.5 V. Probe again while exercising bus traffic with an oscilloscope to confirm proper dominant/recessive transitions and absence of excessive noise.
- Perform wiggle tests on connectors and harness while monitoring bus voltages/communication to reproduce intermittent faults.
- Disconnect non-essential modules or aftermarket devices one at a time (following wiring diagrams) to find a module that causes bus failure.
- If wiring and connectors check OK, suspect gateway/CAN transceiver or affected module; consult manufacturer instructions for module replacement or reflashing.
- After repairs, clear codes, perform full scan, and road-test to verify issue is resolved.
Likely causes
- Corrosion or physical damage at the DLC connector
- Open/short in CAN wiring near DLC or gateway
- Failed termination resistor or disconnected module causing bus-off
- Faulty gateway/CAN transceiver module
- Low battery/poor ground during diagnostic attempt
Fault status
Status
CAN communication fault between DLC and CAN bus — diagnostic tool may not connect and multiple modules may be unreachable. Inspect DLC connector, wiring, termination and gateway/module power.
Repair difficulty: Medium
Diagnostic time: 1-3 hours
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Code
U1702
FIAT
U — Network/User
CAN bus communication between DLC and CAN line
Views:
UK: 5
EN: 14
RU: 8
AI status
Completed
Completed
100%
Causes
- Corroded, bent or damaged DLC connector pins
- Open, shorted or high-resistance CAN_H or CAN_L wiring
- Missing or incorrect termination (open/failed 60 Ω total)
- Intermittent connector or ground connection
- Blown fuse or power supply interruption to gateway/module
- Aftermarket device or trailer wiring interfering with CAN bus
Symptoms
- Unable to communicate with one or more modules via a scan tool at the DLC
- Multiple U-codes or module communication DTCs present
- Intermittent or complete loss of functions controlled over the CAN bus (instruments, body control, immobilizer, etc.)
- No response when attempting reprogramming or key programming
- MIL may or may not be illuminated depending on affected modules
What to check
- Read and record all stored and pending DTCs and freeze frame data using a diagnostic tool
- Visually inspect DLC and nearby harness for corrosion, damage, debris or bent pins
- Verify battery voltage and good chassis/engine grounds before testing
- Inspect fuses and relays that feed gateway/CAN modules
- Check for recent aftermarket installs or trailer wiring connected to DLC area
- Scan which modules respond; note any modules that are missing from the bus
Signal parameters
- Recessive (idle) voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (each ~2.5V)
- Dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2.0 V)
- Expected line termination: ≈ 60 Ω measured between CAN_H and CAN_L (two 120 Ω in parallel)
- Common bus speeds: 125 kb/s, 250 kb/s or 500 kb/s depending on bus — confirm vehicle-specific bit rate
Diagnostic algorithm
- Record all network-related DTCs and note which control modules do not respond.
- Visually inspect DLC and CAN wiring for corrosion, damage, water ingress, loose pins or aftermarket splices; repair as required.
- Verify battery voltage (12.4–12.8 V engine off) and good ground connections.
- Check fuses/power supplies feeding gateway and CAN transceivers; restore if blown.
- Measure resistance between CAN_H and CAN_L at the DLC with ignition off — should be ~60 Ω. If open or very high, isolate sections of the bus to find open/short.
- With key on (engine off) measure idle voltages of CAN_H and CAN_L at the DLC — both ~2.5 V. Probe again while exercising bus traffic with an oscilloscope to confirm proper dominant/recessive transitions and absence of excessive noise.
- Perform wiggle tests on connectors and harness while monitoring bus voltages/communication to reproduce intermittent faults.
- Disconnect non-essential modules or aftermarket devices one at a time (following wiring diagrams) to find a module that causes bus failure.
- If wiring and connectors check OK, suspect gateway/CAN transceiver or affected module; consult manufacturer instructions for module replacement or reflashing.
- After repairs, clear codes, perform full scan, and road-test to verify issue is resolved.
Likely causes
- Corrosion or physical damage at the DLC connector
- Open/short in CAN wiring near DLC or gateway
- Failed termination resistor or disconnected module causing bus-off
- Faulty gateway/CAN transceiver module
- Low battery/poor ground during diagnostic attempt
Fault status
Status
CAN communication fault between DLC and CAN bus — diagnostic tool may not connect and multiple modules may be unreachable. Inspect DLC connector, wiring, termination and gateway/module power.
Repair difficulty: Medium
Diagnostic time: 1-3 hours
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Code
U1702
Generic
U — Network/User
Control Module Communication Fault
Views:
UK: 0
EN: 0
RU: 0
AI status
Completed
Completed
100%
Causes
- Corroded, bent or damaged DLC connector pins
- Open, shorted or high-resistance CAN_H or CAN_L wiring
- Missing or incorrect termination (open/failed 60 Ω total)
- Intermittent connector or ground connection
- Blown fuse or power supply interruption to gateway/module
- Aftermarket device or trailer wiring interfering with CAN bus
Symptoms
- Unable to communicate with one or more modules via a scan tool at the DLC
- Multiple U-codes or module communication DTCs present
- Intermittent or complete loss of functions controlled over the CAN bus (instruments, body control, immobilizer, etc.)
- No response when attempting reprogramming or key programming
- MIL may or may not be illuminated depending on affected modules
What to check
- Read and record all stored and pending DTCs and freeze frame data using a diagnostic tool
- Visually inspect DLC and nearby harness for corrosion, damage, debris or bent pins
- Verify battery voltage and good chassis/engine grounds before testing
- Inspect fuses and relays that feed gateway/CAN modules
- Check for recent aftermarket installs or trailer wiring connected to DLC area
- Scan which modules respond; note any modules that are missing from the bus
Signal parameters
- Recessive (idle) voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (each ~2.5V)
- Dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2.0 V)
- Expected line termination: ≈ 60 Ω measured between CAN_H and CAN_L (two 120 Ω in parallel)
- Common bus speeds: 125 kb/s, 250 kb/s or 500 kb/s depending on bus — confirm vehicle-specific bit rate
Diagnostic algorithm
- Record all network-related DTCs and note which control modules do not respond.
- Visually inspect DLC and CAN wiring for corrosion, damage, water ingress, loose pins or aftermarket splices; repair as required.
- Verify battery voltage (12.4–12.8 V engine off) and good ground connections.
- Check fuses/power supplies feeding gateway and CAN transceivers; restore if blown.
- Measure resistance between CAN_H and CAN_L at the DLC with ignition off — should be ~60 Ω. If open or very high, isolate sections of the bus to find open/short.
- With key on (engine off) measure idle voltages of CAN_H and CAN_L at the DLC — both ~2.5 V. Probe again while exercising bus traffic with an oscilloscope to confirm proper dominant/recessive transitions and absence of excessive noise.
- Perform wiggle tests on connectors and harness while monitoring bus voltages/communication to reproduce intermittent faults.
- Disconnect non-essential modules or aftermarket devices one at a time (following wiring diagrams) to find a module that causes bus failure.
- If wiring and connectors check OK, suspect gateway/CAN transceiver or affected module; consult manufacturer instructions for module replacement or reflashing.
- After repairs, clear codes, perform full scan, and road-test to verify issue is resolved.
Likely causes
- Corrosion or physical damage at the DLC connector
- Open/short in CAN wiring near DLC or gateway
- Failed termination resistor or disconnected module causing bus-off
- Faulty gateway/CAN transceiver module
- Low battery/poor ground during diagnostic attempt
Fault status
Status
CAN communication fault between DLC and CAN bus — diagnostic tool may not connect and multiple modules may be unreachable. Inspect DLC connector, wiring, termination and gateway/module power.
Repair difficulty: Medium
Diagnostic time: 1-3 hours
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Code
U1702
HYUNDAI
U — Network/User
DTCP Sink Decode error.
Views:
UK: 14
EN: 17
RU: 18
AI status
Completed
Completed
100%
Causes
- Corroded, bent or damaged DLC connector pins
- Open, shorted or high-resistance CAN_H or CAN_L wiring
- Missing or incorrect termination (open/failed 60 Ω total)
- Intermittent connector or ground connection
- Blown fuse or power supply interruption to gateway/module
- Aftermarket device or trailer wiring interfering with CAN bus
Symptoms
- Unable to communicate with one or more modules via a scan tool at the DLC
- Multiple U-codes or module communication DTCs present
- Intermittent or complete loss of functions controlled over the CAN bus (instruments, body control, immobilizer, etc.)
- No response when attempting reprogramming or key programming
- MIL may or may not be illuminated depending on affected modules
What to check
- Read and record all stored and pending DTCs and freeze frame data using a diagnostic tool
- Visually inspect DLC and nearby harness for corrosion, damage, debris or bent pins
- Verify battery voltage and good chassis/engine grounds before testing
- Inspect fuses and relays that feed gateway/CAN modules
- Check for recent aftermarket installs or trailer wiring connected to DLC area
- Scan which modules respond; note any modules that are missing from the bus
Signal parameters
- Recessive (idle) voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (each ~2.5V)
- Dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2.0 V)
- Expected line termination: ≈ 60 Ω measured between CAN_H and CAN_L (two 120 Ω in parallel)
- Common bus speeds: 125 kb/s, 250 kb/s or 500 kb/s depending on bus — confirm vehicle-specific bit rate
Diagnostic algorithm
- Record all network-related DTCs and note which control modules do not respond.
- Visually inspect DLC and CAN wiring for corrosion, damage, water ingress, loose pins or aftermarket splices; repair as required.
- Verify battery voltage (12.4–12.8 V engine off) and good ground connections.
- Check fuses/power supplies feeding gateway and CAN transceivers; restore if blown.
- Measure resistance between CAN_H and CAN_L at the DLC with ignition off — should be ~60 Ω. If open or very high, isolate sections of the bus to find open/short.
- With key on (engine off) measure idle voltages of CAN_H and CAN_L at the DLC — both ~2.5 V. Probe again while exercising bus traffic with an oscilloscope to confirm proper dominant/recessive transitions and absence of excessive noise.
- Perform wiggle tests on connectors and harness while monitoring bus voltages/communication to reproduce intermittent faults.
- Disconnect non-essential modules or aftermarket devices one at a time (following wiring diagrams) to find a module that causes bus failure.
- If wiring and connectors check OK, suspect gateway/CAN transceiver or affected module; consult manufacturer instructions for module replacement or reflashing.
- After repairs, clear codes, perform full scan, and road-test to verify issue is resolved.
Likely causes
- Corrosion or physical damage at the DLC connector
- Open/short in CAN wiring near DLC or gateway
- Failed termination resistor or disconnected module causing bus-off
- Faulty gateway/CAN transceiver module
- Low battery/poor ground during diagnostic attempt
Fault status
Status
CAN communication fault between DLC and CAN bus — diagnostic tool may not connect and multiple modules may be unreachable. Inspect DLC connector, wiring, termination and gateway/module power.
Repair difficulty: Medium
Diagnostic time: 1-3 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
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0
Send to email