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DTC codes / U01xx · Lost communication with a control module / U013E

U013ELost Communication With Vacuum Sensor B

U013E is a generic communication fault indicating that a control module on the vehicle's controller area network (CAN) bus has lost contact with the vacuum sensor B, which is typically part of the evaporative emissions or brake booster system. The module that monitors this sensor has stopped receiving valid data messages from it for a calibrated period, so it sets this code and may illuminate the malfunction indicator lamp.

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

Symptoms you may notice

  • Illumination of the check engine light or service vehicle soon message
  • Often no symptoms besides the warning light, especially if the sensor is not critical to engine operation
  • Rough idle or poor driveability if the vacuum sensor B is used for load or purge control
  • Incorrect fuel trims or evap system monitor not completing
  • Intermittent stalling or hesitation if the sensor feeds brake booster or purge logic
  • Other communication codes stored in multiple modules if the CAN bus is disturbed

Common causes, most likely first

  1. Damaged or disconnected wiring at the vacuum sensor B connector
  2. Corroded or loose pins in the sensor or module connector
  3. Failed vacuum sensor B itself
  4. Open or shorted CAN bus wiring between the sensor and its control module
  5. Poor ground or power supply to the sensor or the module that reports it
  6. Software or calibration issue in the control module
  7. Aftermarket accessories or poor previous repairs disturbing the network

How to diagnose and fix it

  1. Scan all modules for communication codes and record freeze-frame data to see when U013E sets
  2. Inspect the vacuum sensor B connector and wiring for damage, corrosion, or loose pins
  3. Check power and ground at the sensor connector with a multimeter and verify reference voltage
  4. Perform a wiggle test on the harness while watching live data for the sensor signal
  5. Check CAN bus resistance and continuity between the sensor and the module that reports the fault
  6. If wiring and power are good, substitute a known-good sensor and clear codes to see if U013E returns
  7. If the code persists after sensor replacement, diagnose the control module and network for internal faults

What most technicians miss on U013E

  • A loose or corroded ground at the sensor or module can mimic a failed sensor and set U013E without any visible wiring damage.
  • The code can be stored by a module that only monitors vacuum sensor B indirectly, so the fault may actually lie in a different module on the same CAN segment.
  • Aftermarket alarms, remote starters, or poor radio installations often disturb CAN bus wiring and cause intermittent U013E faults that disappear when the accessory is removed.
  • Replacing the vacuum sensor B without checking connector pin tension and terminal drag often leads to a repeat code within a few drive cycles.
  • U013E can set alongside evap or brake booster codes, and clearing only the engine module may leave the underlying communication fault active in another module.

Can I keep driving with U013E?

The vehicle is usually safe to drive to a repair shop because the fault is a communication issue rather than a direct safety system failure, but avoid long trips and towing until it is diagnosed. If the check engine light flashes or driveability problems appear, stop driving and have the vehicle towed.

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.

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