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Home / DTC / U0073 — A faulty control module, A problem with the CAN bus

U0073 — A faulty control module, A problem with the CAN bus

Detailed page for trouble code U0073.

34,405codes
59brands
11,914generic
22,491specific
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U0073

AUDI U — Network/User

A faulty control module, A problem with the CAN bus

Brand: AUDI
Type: U — Network/User
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Failed or intermittent control module (ECU/BCM/gateway)
  • Open/short in CAN_H or CAN_L wiring
  • Poor power supply or ground to one or more modules
  • Missing or incorrect termination resistor(s) on the CAN bus
  • Connector corrosion, water ingress or damaged pins
  • Software mismatch or corrupted module software/configuration

Symptoms

  • Malfunction indicator lamps or communication-related warning messages
  • One or more modules report ‘no communication’ or unavailable data
  • Features controlled over CAN do not operate (e.g., instrument cluster, ABS, infotainment)
  • Intermittent system operation or random fault appearance/disappearance
  • Possible loss of drivetrain control or no-start if powertrain module is affected

What to check

  • Read and record all U‑codes and freeze frame data from every module with a professional scan tool
  • Check battery voltage and charging system; ensure stable 12 V supply during tests
  • Visually inspect CAN wiring harnesses, connectors, and module grounds for damage, corrosion, or water intrusion
  • Check for other modules reporting loss of communication or related codes to locate bus segment
  • Measure termination resistance between CAN_H and CAN_L with ignition off (expect ≈60 Ω total)
  • Use a scan tool or CAN log to confirm presence/absence of bus traffic and message IDs

Signal parameters

  • CAN recessive voltage (idle): ~2.5 V on CAN_H and CAN_L (both equal)
  • CAN dominant state: CAN_H ≈3.5 V, CAN_L ≈1.5 V (differential ≈2.0 V)
  • Expected termination: two 120 Ω resistors in parallel ≈60 Ω across CAN_H and CAN_L
  • Common bus bit rates: 125 kbps, 250 kbps, 500 kbps (verify vehicle-specific rate with OEM tool)
  • Voltage tolerance: signals referenced to battery/ignition voltage; tests should be done with stable 12 V supply

Diagnostic algorithm

  1. Prepare: record symptoms, confirm recent repairs/updates, ensure battery charged and ignition on as required
  2. Full scan: read all modules and note communication errors and timestamps
  3. Localize: identify which modules report loss of communication to determine affected bus segment
  4. Power/ground check: verify proper supply and ground at the module(s) that lost communication
  5. Visual/wiggle test: inspect and gently wiggle harnesses/connectors while monitoring bus for changes
  6. Termination test: with ignition off, measure resistance between CAN_H and CAN_L at multiple points — expect ≈60 Ω; an open or very low value indicates termination fault or short
  7. Voltage measurement: with ignition on, measure DC voltage on CAN_H and CAN_L to check for stuck high/low or short to power/ground
  8. Bus traffic: use a scan tool or CAN interface to check message traffic; absence or noisy traffic suggests wiring or module fault
  9. Oscilloscope: capture CAN_H/L waveforms to identify reflections, shorts, high capacitance, or missing dominant bits
  10. Isolate modules: if safe and supported, disconnect suspect modules one at a time and observe bus behavior to find the failing device
  11. Software check: verify correct software/calibration levels and perform reflash or module coding only after wiring and power are confirmed good
  12. Repair/replace: repair damaged wiring/connectors or replace failed module(s). Re-program and clear codes, then re-test for recurrence

Likely causes

  • Gateway/module internal failure preventing bus communication
  • Short to battery or ground on CAN_H or CAN_L at a wiring splice or connector
  • Loose or corroded battery/ignition power or ground to the affected module
  • Loss of termination (open or shorted termination resistor) on one end of the bus
  • Module firmware mismatch after replacement or update not performed

Fault status

⚠️ Status
Control module communication lost or corrupted on CAN bus. Module messages missing or invalid; communication network fault detected.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

U0100 U0101 U0121 U0155 U0077
Repair manuals

Manual library for AUDI

1,160

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Code

U0073

Generic U — Network/User

Control Module Communication Bus A Off

Brand: Generic
Type: U — Network/User
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Failed or intermittent control module (ECU/BCM/gateway)
  • Open/short in CAN_H or CAN_L wiring
  • Poor power supply or ground to one or more modules
  • Missing or incorrect termination resistor(s) on the CAN bus
  • Connector corrosion, water ingress or damaged pins
  • Software mismatch or corrupted module software/configuration

Symptoms

  • Malfunction indicator lamps or communication-related warning messages
  • One or more modules report ‘no communication’ or unavailable data
  • Features controlled over CAN do not operate (e.g., instrument cluster, ABS, infotainment)
  • Intermittent system operation or random fault appearance/disappearance
  • Possible loss of drivetrain control or no-start if powertrain module is affected

What to check

  • Read and record all U‑codes and freeze frame data from every module with a professional scan tool
  • Check battery voltage and charging system; ensure stable 12 V supply during tests
  • Visually inspect CAN wiring harnesses, connectors, and module grounds for damage, corrosion, or water intrusion
  • Check for other modules reporting loss of communication or related codes to locate bus segment
  • Measure termination resistance between CAN_H and CAN_L with ignition off (expect ≈60 Ω total)
  • Use a scan tool or CAN log to confirm presence/absence of bus traffic and message IDs

Signal parameters

  • CAN recessive voltage (idle): ~2.5 V on CAN_H and CAN_L (both equal)
  • CAN dominant state: CAN_H ≈3.5 V, CAN_L ≈1.5 V (differential ≈2.0 V)
  • Expected termination: two 120 Ω resistors in parallel ≈60 Ω across CAN_H and CAN_L
  • Common bus bit rates: 125 kbps, 250 kbps, 500 kbps (verify vehicle-specific rate with OEM tool)
  • Voltage tolerance: signals referenced to battery/ignition voltage; tests should be done with stable 12 V supply

Diagnostic algorithm

  1. Prepare: record symptoms, confirm recent repairs/updates, ensure battery charged and ignition on as required
  2. Full scan: read all modules and note communication errors and timestamps
  3. Localize: identify which modules report loss of communication to determine affected bus segment
  4. Power/ground check: verify proper supply and ground at the module(s) that lost communication
  5. Visual/wiggle test: inspect and gently wiggle harnesses/connectors while monitoring bus for changes
  6. Termination test: with ignition off, measure resistance between CAN_H and CAN_L at multiple points — expect ≈60 Ω; an open or very low value indicates termination fault or short
  7. Voltage measurement: with ignition on, measure DC voltage on CAN_H and CAN_L to check for stuck high/low or short to power/ground
  8. Bus traffic: use a scan tool or CAN interface to check message traffic; absence or noisy traffic suggests wiring or module fault
  9. Oscilloscope: capture CAN_H/L waveforms to identify reflections, shorts, high capacitance, or missing dominant bits
  10. Isolate modules: if safe and supported, disconnect suspect modules one at a time and observe bus behavior to find the failing device
  11. Software check: verify correct software/calibration levels and perform reflash or module coding only after wiring and power are confirmed good
  12. Repair/replace: repair damaged wiring/connectors or replace failed module(s). Re-program and clear codes, then re-test for recurrence

Likely causes

  • Gateway/module internal failure preventing bus communication
  • Short to battery or ground on CAN_H or CAN_L at a wiring splice or connector
  • Loose or corroded battery/ignition power or ground to the affected module
  • Loss of termination (open or shorted termination resistor) on one end of the bus
  • Module firmware mismatch after replacement or update not performed

Fault status

⚠️ Status
Control module communication lost or corrupted on CAN bus. Module messages missing or invalid; communication network fault detected.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

U0100 U0101 U0121 U0155 U0077
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Code

U0073

HYUNDAI U — Network/User

Control Module Communication Bus Off

Brand: HYUNDAI
Type: U — Network/User
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Failed or intermittent control module (ECU/BCM/gateway)
  • Open/short in CAN_H or CAN_L wiring
  • Poor power supply or ground to one or more modules
  • Missing or incorrect termination resistor(s) on the CAN bus
  • Connector corrosion, water ingress or damaged pins
  • Software mismatch or corrupted module software/configuration

Symptoms

  • Malfunction indicator lamps or communication-related warning messages
  • One or more modules report ‘no communication’ or unavailable data
  • Features controlled over CAN do not operate (e.g., instrument cluster, ABS, infotainment)
  • Intermittent system operation or random fault appearance/disappearance
  • Possible loss of drivetrain control or no-start if powertrain module is affected

What to check

  • Read and record all U‑codes and freeze frame data from every module with a professional scan tool
  • Check battery voltage and charging system; ensure stable 12 V supply during tests
  • Visually inspect CAN wiring harnesses, connectors, and module grounds for damage, corrosion, or water intrusion
  • Check for other modules reporting loss of communication or related codes to locate bus segment
  • Measure termination resistance between CAN_H and CAN_L with ignition off (expect ≈60 Ω total)
  • Use a scan tool or CAN log to confirm presence/absence of bus traffic and message IDs

Signal parameters

  • CAN recessive voltage (idle): ~2.5 V on CAN_H and CAN_L (both equal)
  • CAN dominant state: CAN_H ≈3.5 V, CAN_L ≈1.5 V (differential ≈2.0 V)
  • Expected termination: two 120 Ω resistors in parallel ≈60 Ω across CAN_H and CAN_L
  • Common bus bit rates: 125 kbps, 250 kbps, 500 kbps (verify vehicle-specific rate with OEM tool)
  • Voltage tolerance: signals referenced to battery/ignition voltage; tests should be done with stable 12 V supply

Diagnostic algorithm

  1. Prepare: record symptoms, confirm recent repairs/updates, ensure battery charged and ignition on as required
  2. Full scan: read all modules and note communication errors and timestamps
  3. Localize: identify which modules report loss of communication to determine affected bus segment
  4. Power/ground check: verify proper supply and ground at the module(s) that lost communication
  5. Visual/wiggle test: inspect and gently wiggle harnesses/connectors while monitoring bus for changes
  6. Termination test: with ignition off, measure resistance between CAN_H and CAN_L at multiple points — expect ≈60 Ω; an open or very low value indicates termination fault or short
  7. Voltage measurement: with ignition on, measure DC voltage on CAN_H and CAN_L to check for stuck high/low or short to power/ground
  8. Bus traffic: use a scan tool or CAN interface to check message traffic; absence or noisy traffic suggests wiring or module fault
  9. Oscilloscope: capture CAN_H/L waveforms to identify reflections, shorts, high capacitance, or missing dominant bits
  10. Isolate modules: if safe and supported, disconnect suspect modules one at a time and observe bus behavior to find the failing device
  11. Software check: verify correct software/calibration levels and perform reflash or module coding only after wiring and power are confirmed good
  12. Repair/replace: repair damaged wiring/connectors or replace failed module(s). Re-program and clear codes, then re-test for recurrence

Likely causes

  • Gateway/module internal failure preventing bus communication
  • Short to battery or ground on CAN_H or CAN_L at a wiring splice or connector
  • Loose or corroded battery/ignition power or ground to the affected module
  • Loss of termination (open or shorted termination resistor) on one end of the bus
  • Module firmware mismatch after replacement or update not performed

Fault status

⚠️ Status
Control module communication lost or corrupted on CAN bus. Module messages missing or invalid; communication network fault detected.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

U0100 U0101 U0121 U0155 U0077
371

Browse 371 HYUNDAI manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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Code

U0073

ISUZU U — Network/User

Control Module Communication Bus Off

Brand: ISUZU
Type: U — Network/User
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Failed or intermittent control module (ECU/BCM/gateway)
  • Open/short in CAN_H or CAN_L wiring
  • Poor power supply or ground to one or more modules
  • Missing or incorrect termination resistor(s) on the CAN bus
  • Connector corrosion, water ingress or damaged pins
  • Software mismatch or corrupted module software/configuration

Symptoms

  • Malfunction indicator lamps or communication-related warning messages
  • One or more modules report ‘no communication’ or unavailable data
  • Features controlled over CAN do not operate (e.g., instrument cluster, ABS, infotainment)
  • Intermittent system operation or random fault appearance/disappearance
  • Possible loss of drivetrain control or no-start if powertrain module is affected

What to check

  • Read and record all U‑codes and freeze frame data from every module with a professional scan tool
  • Check battery voltage and charging system; ensure stable 12 V supply during tests
  • Visually inspect CAN wiring harnesses, connectors, and module grounds for damage, corrosion, or water intrusion
  • Check for other modules reporting loss of communication or related codes to locate bus segment
  • Measure termination resistance between CAN_H and CAN_L with ignition off (expect ≈60 Ω total)
  • Use a scan tool or CAN log to confirm presence/absence of bus traffic and message IDs

Signal parameters

  • CAN recessive voltage (idle): ~2.5 V on CAN_H and CAN_L (both equal)
  • CAN dominant state: CAN_H ≈3.5 V, CAN_L ≈1.5 V (differential ≈2.0 V)
  • Expected termination: two 120 Ω resistors in parallel ≈60 Ω across CAN_H and CAN_L
  • Common bus bit rates: 125 kbps, 250 kbps, 500 kbps (verify vehicle-specific rate with OEM tool)
  • Voltage tolerance: signals referenced to battery/ignition voltage; tests should be done with stable 12 V supply

Diagnostic algorithm

  1. Prepare: record symptoms, confirm recent repairs/updates, ensure battery charged and ignition on as required
  2. Full scan: read all modules and note communication errors and timestamps
  3. Localize: identify which modules report loss of communication to determine affected bus segment
  4. Power/ground check: verify proper supply and ground at the module(s) that lost communication
  5. Visual/wiggle test: inspect and gently wiggle harnesses/connectors while monitoring bus for changes
  6. Termination test: with ignition off, measure resistance between CAN_H and CAN_L at multiple points — expect ≈60 Ω; an open or very low value indicates termination fault or short
  7. Voltage measurement: with ignition on, measure DC voltage on CAN_H and CAN_L to check for stuck high/low or short to power/ground
  8. Bus traffic: use a scan tool or CAN interface to check message traffic; absence or noisy traffic suggests wiring or module fault
  9. Oscilloscope: capture CAN_H/L waveforms to identify reflections, shorts, high capacitance, or missing dominant bits
  10. Isolate modules: if safe and supported, disconnect suspect modules one at a time and observe bus behavior to find the failing device
  11. Software check: verify correct software/calibration levels and perform reflash or module coding only after wiring and power are confirmed good
  12. Repair/replace: repair damaged wiring/connectors or replace failed module(s). Re-program and clear codes, then re-test for recurrence

Likely causes

  • Gateway/module internal failure preventing bus communication
  • Short to battery or ground on CAN_H or CAN_L at a wiring splice or connector
  • Loose or corroded battery/ignition power or ground to the affected module
  • Loss of termination (open or shorted termination resistor) on one end of the bus
  • Module firmware mismatch after replacement or update not performed

Fault status

⚠️ Status
Control module communication lost or corrupted on CAN bus. Module messages missing or invalid; communication network fault detected.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

U0100 U0101 U0121 U0155 U0077
Repair manuals

Manual library for ISUZU

86

Browse 86 ISUZU manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

ISUZU

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+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
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Code

U0073

LAND ROVER U — Network/User

Communication bus of the control module deactivated

Brand: LAND ROVER
Type: U — Network/User
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Failed or intermittent control module (ECU/BCM/gateway)
  • Open/short in CAN_H or CAN_L wiring
  • Poor power supply or ground to one or more modules
  • Missing or incorrect termination resistor(s) on the CAN bus
  • Connector corrosion, water ingress or damaged pins
  • Software mismatch or corrupted module software/configuration

Symptoms

  • Malfunction indicator lamps or communication-related warning messages
  • One or more modules report ‘no communication’ or unavailable data
  • Features controlled over CAN do not operate (e.g., instrument cluster, ABS, infotainment)
  • Intermittent system operation or random fault appearance/disappearance
  • Possible loss of drivetrain control or no-start if powertrain module is affected

What to check

  • Read and record all U‑codes and freeze frame data from every module with a professional scan tool
  • Check battery voltage and charging system; ensure stable 12 V supply during tests
  • Visually inspect CAN wiring harnesses, connectors, and module grounds for damage, corrosion, or water intrusion
  • Check for other modules reporting loss of communication or related codes to locate bus segment
  • Measure termination resistance between CAN_H and CAN_L with ignition off (expect ≈60 Ω total)
  • Use a scan tool or CAN log to confirm presence/absence of bus traffic and message IDs

Signal parameters

  • CAN recessive voltage (idle): ~2.5 V on CAN_H and CAN_L (both equal)
  • CAN dominant state: CAN_H ≈3.5 V, CAN_L ≈1.5 V (differential ≈2.0 V)
  • Expected termination: two 120 Ω resistors in parallel ≈60 Ω across CAN_H and CAN_L
  • Common bus bit rates: 125 kbps, 250 kbps, 500 kbps (verify vehicle-specific rate with OEM tool)
  • Voltage tolerance: signals referenced to battery/ignition voltage; tests should be done with stable 12 V supply

Diagnostic algorithm

  1. Prepare: record symptoms, confirm recent repairs/updates, ensure battery charged and ignition on as required
  2. Full scan: read all modules and note communication errors and timestamps
  3. Localize: identify which modules report loss of communication to determine affected bus segment
  4. Power/ground check: verify proper supply and ground at the module(s) that lost communication
  5. Visual/wiggle test: inspect and gently wiggle harnesses/connectors while monitoring bus for changes
  6. Termination test: with ignition off, measure resistance between CAN_H and CAN_L at multiple points — expect ≈60 Ω; an open or very low value indicates termination fault or short
  7. Voltage measurement: with ignition on, measure DC voltage on CAN_H and CAN_L to check for stuck high/low or short to power/ground
  8. Bus traffic: use a scan tool or CAN interface to check message traffic; absence or noisy traffic suggests wiring or module fault
  9. Oscilloscope: capture CAN_H/L waveforms to identify reflections, shorts, high capacitance, or missing dominant bits
  10. Isolate modules: if safe and supported, disconnect suspect modules one at a time and observe bus behavior to find the failing device
  11. Software check: verify correct software/calibration levels and perform reflash or module coding only after wiring and power are confirmed good
  12. Repair/replace: repair damaged wiring/connectors or replace failed module(s). Re-program and clear codes, then re-test for recurrence

Likely causes

  • Gateway/module internal failure preventing bus communication
  • Short to battery or ground on CAN_H or CAN_L at a wiring splice or connector
  • Loose or corroded battery/ignition power or ground to the affected module
  • Loss of termination (open or shorted termination resistor) on one end of the bus
  • Module firmware mismatch after replacement or update not performed

Fault status

⚠️ Status
Control module communication lost or corrupted on CAN bus. Module messages missing or invalid; communication network fault detected.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

U0100 U0101 U0121 U0155 U0077
320

Browse 320 LAND ROVER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

LAND ROVER

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+100 karma for a short comment :)
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Code

U0073

MERCEDES-BENZ U — Network/User

Control Module Communications Bus Off

Brand: MERCEDES-BENZ
Type: U — Network/User
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Failed or intermittent control module (ECU/BCM/gateway)
  • Open/short in CAN_H or CAN_L wiring
  • Poor power supply or ground to one or more modules
  • Missing or incorrect termination resistor(s) on the CAN bus
  • Connector corrosion, water ingress or damaged pins
  • Software mismatch or corrupted module software/configuration

Symptoms

  • Malfunction indicator lamps or communication-related warning messages
  • One or more modules report ‘no communication’ or unavailable data
  • Features controlled over CAN do not operate (e.g., instrument cluster, ABS, infotainment)
  • Intermittent system operation or random fault appearance/disappearance
  • Possible loss of drivetrain control or no-start if powertrain module is affected

What to check

  • Read and record all U‑codes and freeze frame data from every module with a professional scan tool
  • Check battery voltage and charging system; ensure stable 12 V supply during tests
  • Visually inspect CAN wiring harnesses, connectors, and module grounds for damage, corrosion, or water intrusion
  • Check for other modules reporting loss of communication or related codes to locate bus segment
  • Measure termination resistance between CAN_H and CAN_L with ignition off (expect ≈60 Ω total)
  • Use a scan tool or CAN log to confirm presence/absence of bus traffic and message IDs

Signal parameters

  • CAN recessive voltage (idle): ~2.5 V on CAN_H and CAN_L (both equal)
  • CAN dominant state: CAN_H ≈3.5 V, CAN_L ≈1.5 V (differential ≈2.0 V)
  • Expected termination: two 120 Ω resistors in parallel ≈60 Ω across CAN_H and CAN_L
  • Common bus bit rates: 125 kbps, 250 kbps, 500 kbps (verify vehicle-specific rate with OEM tool)
  • Voltage tolerance: signals referenced to battery/ignition voltage; tests should be done with stable 12 V supply

Diagnostic algorithm

  1. Prepare: record symptoms, confirm recent repairs/updates, ensure battery charged and ignition on as required
  2. Full scan: read all modules and note communication errors and timestamps
  3. Localize: identify which modules report loss of communication to determine affected bus segment
  4. Power/ground check: verify proper supply and ground at the module(s) that lost communication
  5. Visual/wiggle test: inspect and gently wiggle harnesses/connectors while monitoring bus for changes
  6. Termination test: with ignition off, measure resistance between CAN_H and CAN_L at multiple points — expect ≈60 Ω; an open or very low value indicates termination fault or short
  7. Voltage measurement: with ignition on, measure DC voltage on CAN_H and CAN_L to check for stuck high/low or short to power/ground
  8. Bus traffic: use a scan tool or CAN interface to check message traffic; absence or noisy traffic suggests wiring or module fault
  9. Oscilloscope: capture CAN_H/L waveforms to identify reflections, shorts, high capacitance, or missing dominant bits
  10. Isolate modules: if safe and supported, disconnect suspect modules one at a time and observe bus behavior to find the failing device
  11. Software check: verify correct software/calibration levels and perform reflash or module coding only after wiring and power are confirmed good
  12. Repair/replace: repair damaged wiring/connectors or replace failed module(s). Re-program and clear codes, then re-test for recurrence

Likely causes

  • Gateway/module internal failure preventing bus communication
  • Short to battery or ground on CAN_H or CAN_L at a wiring splice or connector
  • Loose or corroded battery/ignition power or ground to the affected module
  • Loss of termination (open or shorted termination resistor) on one end of the bus
  • Module firmware mismatch after replacement or update not performed

Fault status

⚠️ Status
Control module communication lost or corrupted on CAN bus. Module messages missing or invalid; communication network fault detected.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

U0100 U0101 U0121 U0155 U0077
856

Browse 856 MERCEDES-BENZ manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

MERCEDES-BENZ

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