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DTC codes / U01xx · Lost communication with a control module / U010B

U010BLost Communication With Exhaust Gas Recirculation Control Module B

U010B indicates that the engine control module or another primary controller has lost the controller area network (CAN) communication link with the exhaust gas recirculation (EGR) control module B. The computer has detected that expected periodic messages from that specific module have stopped arriving within the required time window, which sets the code and usually commands the EGR system into a default or disabled state.

SystemNetwork
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyProfessional
AreaLost communication with a control module

Symptoms you may notice

  • Illumination of the malfunction indicator lamp (check engine light) with no other obvious drivability complaint.
  • Rough idle or slight hesitation during light-throttle acceleration if the EGR valve defaults to a fixed position.
  • Elevated nitrogen oxide emissions that may cause a state inspection failure even when the engine feels normal.
  • Intermittent stalling or surging at steady cruise if the module drops communication only under certain vibration or temperature conditions.
  • A stored U010B accompanied by other U-codes for modules on the same CAN segment, indicating a shared bus fault rather than a module-specific failure.
  • No symptoms besides the warning light in many cases, because the powertrain control module substitutes a default EGR strategy that keeps the engine running acceptably.

Common causes, most likely first

  1. Damaged, chafed, or corroded wiring in the CAN bus circuit between the EGR control module B and the main gateway or powertrain control module.
  2. A failed EGR control module B, often due to internal circuit board faults or water intrusion into the module connector.
  3. Loose or backed-out terminals in the EGR module connector or in the in-line harness connectors along the CAN bus path.
  4. A shorted or open CAN high or CAN low wire caused by rodent damage, road debris, or previous repair work pinching the harness.
  5. Low battery voltage or a weak ground connection at the EGR module, which prevents the module from powering up and transmitting on the network.
  6. A network communication fault on another module that shares the same CAN segment, causing the EGR module B messages to be dropped or corrupted.
  7. Aftermarket electronic accessories wired into the CAN bus without proper isolation, introducing noise that disrupts module communication.

How to diagnose and fix it

  1. Connect a scan tool and record all stored codes, then check whether U010B is current or history and whether other modules on the same bus are also reporting communication loss.
  2. Inspect the EGR control module B connector for corrosion, water intrusion, loose pins, and backed-out terminals, and clean or repair as needed.
  3. Perform a voltage drop test on the module power and ground circuits to confirm the module receives full battery voltage and a clean ground.
  4. Measure resistance and check for shorts to ground or power on the CAN high and CAN low wires between the EGR module and the gateway or powertrain control module.
  5. If wiring and power are good, substitute a known-good EGR control module B or perform a module swap with a compatible unit to see whether communication returns.
  6. Clear the codes and road-test the vehicle through several drive cycles to confirm the U010B does not return and that the EGR monitor completes.
  7. If the fault persists after module replacement, check for software updates or configuration programming required for the new module and verify the CAN bus topology for any other failing nodes.

What a U010B often really means

  • A U010B is frequently set by a poor ground at the EGR module rather than by a dead module, so technicians who replace the module first often find the code returns within a few drive cycles.
  • The code can be stored intermittently by vibration or heat that opens a marginal connection only when the engine is at operating temperature, which means a cold static test may show no fault at all.
  • A single failed module on the CAN bus can pull the entire bus down and set communication codes for several unrelated modules, so always check whether other U-codes share the same bus segment before condemning the EGR module.
  • Aftermarket remote starters, alarm systems, and dash cameras tapped into the CAN wiring are a commonly missed cause of intermittent U010B because they introduce noise or load that disrupts module messaging.
  • The powertrain control module may keep the EGR valve at a fixed default position when communication is lost, so the vehicle can pass a basic driveability check while still failing an emissions inspection.

Can I keep driving with U010B?

The vehicle is generally safe to drive to a repair shop because the engine control module substitutes a default EGR strategy, but avoid long-distance travel or heavy load until the fault is repaired. If the check engine light flashes or the engine runs rough, stop driving and have the vehicle towed to prevent damage to the catalytic converter.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

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

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