Corroded, loose, or damaged connectors at the module or power distribution point; Chafed or broken wires in the power circuit B or C harness, often near sharp edges or heat sources; Blown or improperly rated fuses in the power feed circuits; Faulty power distribution module or relay supplying the circuits; Voltage drop across a shared ground connection causing inconsistent reference voltages; Internal fault in the control module affecting its power input sensing circuitry; Aftermarket accessories improperly tapped into the power circuits, altering load characteristics

DTC codes / U30xx · Network wiring and bus faults / U3019

U3019Control Module Input Power Circuit B/C Correlation

Q: What does code U3019 mean?

Control Module Input Power Circuit B/C Correlation. U3019 is a generic network communication code indicating that a control module has detected a correlation fault between its input power circuits B and C, meaning the voltages or signals on these two power feeds do not agree with expected values. The module compares the two inputs and sets this code when the difference exceeds a calibrated threshold, often due to a wiring, connector, or power supply issue rather than an internal module failure.

U3019 is a generic network communication code indicating that a control module has detected a correlation fault between its input power circuits B and C, meaning the voltages or signals on these two power feeds do not agree with expected values. The module compares the two inputs and sets this code when the difference exceeds a calibrated threshold, often due to a wiring, connector, or power supply issue rather than an internal module failure.

SystemNetwork

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaNetwork wiring and bus faults

Symptoms you may notice

Illumination of the malfunction indicator lamp (MIL) or a module-specific warning light
Often no symptoms besides the warning light, especially if the fault is intermittent
Intermittent electrical glitches such as flickering lights, radio resets, or erratic gauge behavior
Multiple unrelated trouble codes stored in various modules due to shared power feeds
A no-start condition or stalling if the affected module loses power entirely
Reduced functionality of systems controlled by the affected module, such as climate control or lighting

Common causes, most likely first

Corroded, loose, or damaged connectors at the module or power distribution point
Chafed or broken wires in the power circuit B or C harness, often near sharp edges or heat sources
Blown or improperly rated fuses in the power feed circuits
Faulty power distribution module or relay supplying the circuits
Voltage drop across a shared ground connection causing inconsistent reference voltages
Internal fault in the control module affecting its power input sensing circuitry
Aftermarket accessories improperly tapped into the power circuits, altering load characteristics

How to diagnose and fix it

Retrieve all stored codes and freeze-frame data to identify which module set U3019 and any related codes
Visually inspect the module connectors and power distribution area for corrosion, loose pins, or damaged wiring
Check the fuses and relays for circuits B and C, verifying correct rating and continuity
Perform voltage drop tests on both power circuits under load to compare actual voltages at the module
Wiggle-test the harness while monitoring live data to reveal intermittent opens or shorts
Repair or replace damaged wiring, connectors, or fuses as needed, then clear codes and verify the fault is gone
If all external circuits test good, substitute a known-good module or perform a module reprogramming before replacement

Power circuit correlation faults often misdiagnosed

Many technicians replace the control module prematurely when the real cause is a voltage drop on one power feed due to a corroded ground or fuse box terminal.
U3019 can be set by a weak battery or charging system issue that causes momentary voltage sags, so always load-test the battery and check charging voltage first.
The code does not always indicate a hard failure; intermittent faults from vibration or temperature changes may require extensive wiggle-testing and data logging.
Aftermarket alarms, remote starters, or audio equipment tapped into factory power circuits frequently disturb the correlation between B and C inputs.
A module that sets U3019 may still function normally, but the underlying power issue can cause other modules to set unrelated codes, leading to misdiagnosis.

Can I keep driving with U3019?

If the vehicle runs and drives normally, you can drive it to a repair shop, but avoid long trips or heavy electrical loads until the fault is diagnosed. If the engine stalls, won't start, or multiple warning lights appear, stop driving and have the vehicle towed to prevent safety risks.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.