Code
U0115
Generic
U — Network/User
Lost Communication With ECM/PCM B
Views:
UK: 30
EN: 94
RU: 46
AI status
Completed
Completed
100%
Causes
- Open or short in communication bus wiring (CAN high or CAN low)
- Loss of power or ground to ECM/PCM B (blown fuse, open feed, bad ground)
- Faulty ECM/PCM B (internal failure)
- Missing or failed bus termination resistor(s)
- Corroded or loose connector at ECM/PCM B or junctions
- Network interference from aftermarket accessories or modules
Symptoms
- MIL (Check Engine) or other warning lamps illuminated
- Related systems that depend on ECM/PCM B may be nonfunctional or degraded
- Reduced drivability or limp-in mode if ECM/PCM B controls engine management
- Inability for scan tool to communicate with ECM/PCM B
- Intermittent faults or communication dropouts
What to check
- Read all stored and pending codes from all modules; record freeze frame and timestamp
- Check for other network U-codes (indicates broader bus issue)
- Verify ECM/PCM B fuse(s) and main power feed(s) with key ON
- Inspect ECM/PCM B connector and wiring for corrosion, pin damage, or loose terminals
- Measure key ON battery voltage at ECM/PCM B power pin(s)
- Check ground integrity at ECM/PCM B (resistance to chassis < 1 ohm)
Signal parameters
- Battery voltage at ECM/PCM B: ~12.0–14.5 V with engine running (key ON engine OFF ~12.0 V)
- CAN bus idle voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (recessive state)
- CAN dominant state during traffic: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2.0 V)
- Termination resistance across CAN_H and CAN_L with ignition OFF: ~60 ohms (two 120 Ω terminators in parallel)
- Wake/standby signal voltages vary by manufacturer — consult service data for specific wake line values
Diagnostic algorithm
- Confirm the code: Connect a manufacturer-capable scan tool. Read U0115 and any related codes from all modules and note freeze frame data.
- Check for broad network faults: If multiple modules show communication loss, suspect a bus power/ground, termination, or main bus short rather than a single module.
- Verify power and ground to ECM/PCM B: With key ON, check fuse(s) and measure battery voltage at module power pins; check ground resistance to chassis.
- Inspect connectors and wiring: Visually and physically inspect harness, pins and shield near ECM/PCM B and junction points for corrosion, damage, or water intrusion.
- Check bus termination: With ignition OFF, measure resistance between CAN_H and CAN_L at a convenient point. A significantly different value than specified indicates missing/failed terminator or short to supply/ground.
- Verify bus voltages and activity: With key ON, measure CAN_H and CAN_L voltages. Use a scope or high-speed scan tool to verify data activity and correct differential transitions. Look for bus-off conditions or constant dominant level.
- Isolate wiring: If bus wiring looks suspect, disconnect ECM/PCM B and check for changes on the bus. Wiggle test harness while monitoring bus to reproduce intermittent faults.
- Check for aftermarket interference: Disconnect non-factory modules or adapters (alarms, telematics) and retest.
- Reflash/verify software: If hardware passes tests, verify module calibration and software level per manufacturer procedures and perform reprogramming if recommended.
- Replace module as last resort: If ECM/PCM B fails power/ground, wiring, termination and software checks and communication cannot be restored, consider module replacement and reprogramming. After any repair, clear codes and road-test to confirm the issue is resolved.
Likely causes
- Blown fuse or lost power/ground to ECM/PCM B
- Open or shorted CAN bus wiring near ECM/PCM B
- Failed or loose connector at ECM/PCM B
- Missing/failed termination resistor causing bus error
- ECM/PCM B hardware or firmware fault
Fault status
Status
Lost Communication With ECM/PCM B — no response from ECM/PCM B on vehicle communication bus
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
U0115
HYUNDAI
U — Network/User
Lost Communication With ECM/PCM “B”
Views:
UK: 49
EN: 74
RU: 38
AI status
Completed
Completed
100%
Causes
- Open or short in communication bus wiring (CAN high or CAN low)
- Loss of power or ground to ECM/PCM B (blown fuse, open feed, bad ground)
- Faulty ECM/PCM B (internal failure)
- Missing or failed bus termination resistor(s)
- Corroded or loose connector at ECM/PCM B or junctions
- Network interference from aftermarket accessories or modules
Symptoms
- MIL (Check Engine) or other warning lamps illuminated
- Related systems that depend on ECM/PCM B may be nonfunctional or degraded
- Reduced drivability or limp-in mode if ECM/PCM B controls engine management
- Inability for scan tool to communicate with ECM/PCM B
- Intermittent faults or communication dropouts
What to check
- Read all stored and pending codes from all modules; record freeze frame and timestamp
- Check for other network U-codes (indicates broader bus issue)
- Verify ECM/PCM B fuse(s) and main power feed(s) with key ON
- Inspect ECM/PCM B connector and wiring for corrosion, pin damage, or loose terminals
- Measure key ON battery voltage at ECM/PCM B power pin(s)
- Check ground integrity at ECM/PCM B (resistance to chassis < 1 ohm)
Signal parameters
- Battery voltage at ECM/PCM B: ~12.0–14.5 V with engine running (key ON engine OFF ~12.0 V)
- CAN bus idle voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (recessive state)
- CAN dominant state during traffic: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2.0 V)
- Termination resistance across CAN_H and CAN_L with ignition OFF: ~60 ohms (two 120 Ω terminators in parallel)
- Wake/standby signal voltages vary by manufacturer — consult service data for specific wake line values
Diagnostic algorithm
- Confirm the code: Connect a manufacturer-capable scan tool. Read U0115 and any related codes from all modules and note freeze frame data.
- Check for broad network faults: If multiple modules show communication loss, suspect a bus power/ground, termination, or main bus short rather than a single module.
- Verify power and ground to ECM/PCM B: With key ON, check fuse(s) and measure battery voltage at module power pins; check ground resistance to chassis.
- Inspect connectors and wiring: Visually and physically inspect harness, pins and shield near ECM/PCM B and junction points for corrosion, damage, or water intrusion.
- Check bus termination: With ignition OFF, measure resistance between CAN_H and CAN_L at a convenient point. A significantly different value than specified indicates missing/failed terminator or short to supply/ground.
- Verify bus voltages and activity: With key ON, measure CAN_H and CAN_L voltages. Use a scope or high-speed scan tool to verify data activity and correct differential transitions. Look for bus-off conditions or constant dominant level.
- Isolate wiring: If bus wiring looks suspect, disconnect ECM/PCM B and check for changes on the bus. Wiggle test harness while monitoring bus to reproduce intermittent faults.
- Check for aftermarket interference: Disconnect non-factory modules or adapters (alarms, telematics) and retest.
- Reflash/verify software: If hardware passes tests, verify module calibration and software level per manufacturer procedures and perform reprogramming if recommended.
- Replace module as last resort: If ECM/PCM B fails power/ground, wiring, termination and software checks and communication cannot be restored, consider module replacement and reprogramming. After any repair, clear codes and road-test to confirm the issue is resolved.
Likely causes
- Blown fuse or lost power/ground to ECM/PCM B
- Open or shorted CAN bus wiring near ECM/PCM B
- Failed or loose connector at ECM/PCM B
- Missing/failed termination resistor causing bus error
- ECM/PCM B hardware or firmware fault
Fault status
Status
Lost Communication With ECM/PCM B — no response from ECM/PCM B on vehicle communication bus
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
U0115
LAND ROVER
U — Network/User
Lost communication with the engine control module / module power train control B
Views:
UK: 26
EN: 66
RU: 33
AI status
Completed
Completed
100%
Causes
- Open or short in communication bus wiring (CAN high or CAN low)
- Loss of power or ground to ECM/PCM B (blown fuse, open feed, bad ground)
- Faulty ECM/PCM B (internal failure)
- Missing or failed bus termination resistor(s)
- Corroded or loose connector at ECM/PCM B or junctions
- Network interference from aftermarket accessories or modules
Symptoms
- MIL (Check Engine) or other warning lamps illuminated
- Related systems that depend on ECM/PCM B may be nonfunctional or degraded
- Reduced drivability or limp-in mode if ECM/PCM B controls engine management
- Inability for scan tool to communicate with ECM/PCM B
- Intermittent faults or communication dropouts
What to check
- Read all stored and pending codes from all modules; record freeze frame and timestamp
- Check for other network U-codes (indicates broader bus issue)
- Verify ECM/PCM B fuse(s) and main power feed(s) with key ON
- Inspect ECM/PCM B connector and wiring for corrosion, pin damage, or loose terminals
- Measure key ON battery voltage at ECM/PCM B power pin(s)
- Check ground integrity at ECM/PCM B (resistance to chassis < 1 ohm)
Signal parameters
- Battery voltage at ECM/PCM B: ~12.0–14.5 V with engine running (key ON engine OFF ~12.0 V)
- CAN bus idle voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (recessive state)
- CAN dominant state during traffic: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2.0 V)
- Termination resistance across CAN_H and CAN_L with ignition OFF: ~60 ohms (two 120 Ω terminators in parallel)
- Wake/standby signal voltages vary by manufacturer — consult service data for specific wake line values
Diagnostic algorithm
- Confirm the code: Connect a manufacturer-capable scan tool. Read U0115 and any related codes from all modules and note freeze frame data.
- Check for broad network faults: If multiple modules show communication loss, suspect a bus power/ground, termination, or main bus short rather than a single module.
- Verify power and ground to ECM/PCM B: With key ON, check fuse(s) and measure battery voltage at module power pins; check ground resistance to chassis.
- Inspect connectors and wiring: Visually and physically inspect harness, pins and shield near ECM/PCM B and junction points for corrosion, damage, or water intrusion.
- Check bus termination: With ignition OFF, measure resistance between CAN_H and CAN_L at a convenient point. A significantly different value than specified indicates missing/failed terminator or short to supply/ground.
- Verify bus voltages and activity: With key ON, measure CAN_H and CAN_L voltages. Use a scope or high-speed scan tool to verify data activity and correct differential transitions. Look for bus-off conditions or constant dominant level.
- Isolate wiring: If bus wiring looks suspect, disconnect ECM/PCM B and check for changes on the bus. Wiggle test harness while monitoring bus to reproduce intermittent faults.
- Check for aftermarket interference: Disconnect non-factory modules or adapters (alarms, telematics) and retest.
- Reflash/verify software: If hardware passes tests, verify module calibration and software level per manufacturer procedures and perform reprogramming if recommended.
- Replace module as last resort: If ECM/PCM B fails power/ground, wiring, termination and software checks and communication cannot be restored, consider module replacement and reprogramming. After any repair, clear codes and road-test to confirm the issue is resolved.
Likely causes
- Blown fuse or lost power/ground to ECM/PCM B
- Open or shorted CAN bus wiring near ECM/PCM B
- Failed or loose connector at ECM/PCM B
- Missing/failed termination resistor causing bus error
- ECM/PCM B hardware or firmware fault
Fault status
Status
Lost Communication With ECM/PCM B — no response from ECM/PCM B on vehicle communication bus
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
Similar codes
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Was this AI description helpful?
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