Code
U0146
Generic
U — Network/User
Lost Communication With Serial Data Gateway Module A
Views:
UK: 24
EN: 42
RU: 28
AI status
Completed
Completed
100%
Causes
- Open or short in CAN/serial data wiring or connectors
- Faulty Serial Data Gateway Module A (SDGM-A)
- Blown fuse or loss of module power/ground
- Network bus off condition or missing termination
- Software/firmware error or module needing a reflash
- Aftermarket device or accessory interfering with the bus
Symptoms
- One or more warning lamps (check engine, ABS, airbag, etc.)
- Loss of multiple vehicle functions that rely on networked modules
- Intermittent or permanent loss of instrument cluster messages
- Unresponsive vehicle features (doors, HVAC, telematics)
- Diagnostic scanner cannot communicate with the gateway module
What to check
- Check battery voltage (should be >12.4 V with key off and >13.0 V with engine running)
- Inspect fuses related to gateway and network power/IGN circuits
- Visually inspect connector pins at the gateway and nearby junctions for corrosion or bent pins
- Use a scan tool to list modules and note which modules are missing or reporting U-codes
- Check for aftermarket modules or recent wiring work that could affect the bus
- Quickly measure CAN bus idle voltages with vehicle key on (see signal_params)
Signal parameters
- CAN high (recessive): approx. 2.4–2.6 V
- CAN low (recessive): approx. 2.4–2.6 V
- CAN high (dominant): approx. 3.5–3.7 V; CAN low (dominant): approx. 1.3–1.5 V
- CAN differential (dominant): approx. 1.8–2.5 V
- Termination resistance (two terminators in parallel): approx. 60 Ω across CANH–CANL
- Common bus data rates: 125 kbps, 250 kbps, 500 kbps (verify vehicle-specific rate with factory data)
Diagnostic algorithm
- Retrieve freeze frame and full DTC list with a capable scan tool; record any other U- or P-codes and module presence.
- Verify battery state-of-charge and charging system; charge battery to full if low before continuing.
- Inspect fuses related to gateway and CAN/J1939 power (replace any blown fuses and re-test).
- Visually inspect the gateway module connector and harness for damage, corrosion, loose pins or water ingress; repair as needed.
- With ignition ON (engine off), measure CANH and CANL voltages at the gateway connector and at another known-good module location. Compare to signal_params. If voltages are out of range, isolate wiring fault.
- Measure termination resistance between CANH and CANL at two end-points; expect ~60 Ω. If open or shorted, trace and repair wiring or remove shorted accessory.
Likely causes
- Faulty or loose connector at the gateway module
- Damaged CAN high/low wires (chafed, pinched, or shorted)
- Battery disconnected or low voltage during ignition cycle
- Failed internal power supply or ground inside the gateway
- Missing or failed network terminator (≈120 Ω across CANH-CANL at each end)
- Recent module replacement that requires programming
Fault status
Status
Lost Communication With Serial Data Gateway Module A — gateway is not responding on vehicle serial/CAN network; messages not received by other modules.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
U0146
HYUNDAI
U — Network/User
Lost Communication With Gateway “A” | Lost Communication with GateWay “A”
Views:
UK: 13
EN: 34
RU: 23
AI status
Completed
Completed
100%
Causes
- Open or short in CAN/serial data wiring or connectors
- Faulty Serial Data Gateway Module A (SDGM-A)
- Blown fuse or loss of module power/ground
- Network bus off condition or missing termination
- Software/firmware error or module needing a reflash
- Aftermarket device or accessory interfering with the bus
Symptoms
- One or more warning lamps (check engine, ABS, airbag, etc.)
- Loss of multiple vehicle functions that rely on networked modules
- Intermittent or permanent loss of instrument cluster messages
- Unresponsive vehicle features (doors, HVAC, telematics)
- Diagnostic scanner cannot communicate with the gateway module
What to check
- Check battery voltage (should be >12.4 V with key off and >13.0 V with engine running)
- Inspect fuses related to gateway and network power/IGN circuits
- Visually inspect connector pins at the gateway and nearby junctions for corrosion or bent pins
- Use a scan tool to list modules and note which modules are missing or reporting U-codes
- Check for aftermarket modules or recent wiring work that could affect the bus
- Quickly measure CAN bus idle voltages with vehicle key on (see signal_params)
Signal parameters
- CAN high (recessive): approx. 2.4–2.6 V
- CAN low (recessive): approx. 2.4–2.6 V
- CAN high (dominant): approx. 3.5–3.7 V; CAN low (dominant): approx. 1.3–1.5 V
- CAN differential (dominant): approx. 1.8–2.5 V
- Termination resistance (two terminators in parallel): approx. 60 Ω across CANH–CANL
- Common bus data rates: 125 kbps, 250 kbps, 500 kbps (verify vehicle-specific rate with factory data)
Diagnostic algorithm
- Retrieve freeze frame and full DTC list with a capable scan tool; record any other U- or P-codes and module presence.
- Verify battery state-of-charge and charging system; charge battery to full if low before continuing.
- Inspect fuses related to gateway and CAN/J1939 power (replace any blown fuses and re-test).
- Visually inspect the gateway module connector and harness for damage, corrosion, loose pins or water ingress; repair as needed.
- With ignition ON (engine off), measure CANH and CANL voltages at the gateway connector and at another known-good module location. Compare to signal_params. If voltages are out of range, isolate wiring fault.
- Measure termination resistance between CANH and CANL at two end-points; expect ~60 Ω. If open or shorted, trace and repair wiring or remove shorted accessory.
Likely causes
- Faulty or loose connector at the gateway module
- Damaged CAN high/low wires (chafed, pinched, or shorted)
- Battery disconnected or low voltage during ignition cycle
- Failed internal power supply or ground inside the gateway
- Missing or failed network terminator (≈120 Ω across CANH-CANL at each end)
- Recent module replacement that requires programming
Fault status
Status
Lost Communication With Serial Data Gateway Module A — gateway is not responding on vehicle serial/CAN network; messages not received by other modules.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
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Code
U0146
LAND ROVER
U — Network/User
Lost communication with gateway A
Views:
UK: 8
EN: 27
RU: 14
AI status
Completed
Completed
100%
Causes
- Open or short in CAN/serial data wiring or connectors
- Faulty Serial Data Gateway Module A (SDGM-A)
- Blown fuse or loss of module power/ground
- Network bus off condition or missing termination
- Software/firmware error or module needing a reflash
- Aftermarket device or accessory interfering with the bus
Symptoms
- One or more warning lamps (check engine, ABS, airbag, etc.)
- Loss of multiple vehicle functions that rely on networked modules
- Intermittent or permanent loss of instrument cluster messages
- Unresponsive vehicle features (doors, HVAC, telematics)
- Diagnostic scanner cannot communicate with the gateway module
What to check
- Check battery voltage (should be >12.4 V with key off and >13.0 V with engine running)
- Inspect fuses related to gateway and network power/IGN circuits
- Visually inspect connector pins at the gateway and nearby junctions for corrosion or bent pins
- Use a scan tool to list modules and note which modules are missing or reporting U-codes
- Check for aftermarket modules or recent wiring work that could affect the bus
- Quickly measure CAN bus idle voltages with vehicle key on (see signal_params)
Signal parameters
- CAN high (recessive): approx. 2.4–2.6 V
- CAN low (recessive): approx. 2.4–2.6 V
- CAN high (dominant): approx. 3.5–3.7 V; CAN low (dominant): approx. 1.3–1.5 V
- CAN differential (dominant): approx. 1.8–2.5 V
- Termination resistance (two terminators in parallel): approx. 60 Ω across CANH–CANL
- Common bus data rates: 125 kbps, 250 kbps, 500 kbps (verify vehicle-specific rate with factory data)
Diagnostic algorithm
- Retrieve freeze frame and full DTC list with a capable scan tool; record any other U- or P-codes and module presence.
- Verify battery state-of-charge and charging system; charge battery to full if low before continuing.
- Inspect fuses related to gateway and CAN/J1939 power (replace any blown fuses and re-test).
- Visually inspect the gateway module connector and harness for damage, corrosion, loose pins or water ingress; repair as needed.
- With ignition ON (engine off), measure CANH and CANL voltages at the gateway connector and at another known-good module location. Compare to signal_params. If voltages are out of range, isolate wiring fault.
- Measure termination resistance between CANH and CANL at two end-points; expect ~60 Ω. If open or shorted, trace and repair wiring or remove shorted accessory.
Likely causes
- Faulty or loose connector at the gateway module
- Damaged CAN high/low wires (chafed, pinched, or shorted)
- Battery disconnected or low voltage during ignition cycle
- Failed internal power supply or ground inside the gateway
- Missing or failed network terminator (≈120 Ω across CANH-CANL at each end)
- Recent module replacement that requires programming
Fault status
Status
Lost Communication With Serial Data Gateway Module A — gateway is not responding on vehicle serial/CAN network; messages not received by other modules.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
Similar codes
Workshop Manuals
Repair manuals for LAND ROVER
2
Land Rover Defender 300Tdi — Workshop Manual (1996 model year)
Workshop ManualLand Rover Defender Workshop Manual Supplement & Body Repair Manual (1999 & 2002 MY)
Workshop ManualYour experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email