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DTC codes / U01xx · Lost communication with a control module / U0136

U0136Lost Communication with Park Brake Module B

U0136 is a network communication code indicating that the primary control module has lost the controller area network (CAN) messages it expects from the park brake module, designated as module B. The computer has detected a sustained absence of the periodic status frames that the park brake module normally broadcasts, which can be caused by a power, ground, or data bus fault rather than a failed module.

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

Symptoms you may notice

  • Illumination of the anti-lock brake system (ABS) and/or traction control warning lights on the dashboard
  • A red or amber parking brake warning light that stays on or flashes even when the brake is released
  • The electronic parking brake may fail to apply or release automatically, or may not respond to the switch
  • Often no symptoms besides the warning light, with the vehicle driving and braking normally
  • A stored U0136 code in the primary control module with no other drivability complaints
  • In some vehicles, a chime or message center alert stating that the park brake system needs service

Common causes, most likely first

  1. A blown fuse or poor connection in the power supply circuit to the park brake module
  2. Corroded, loose, or damaged ground connection at the park brake module or its mounting point
  3. Open or shorted CAN bus wiring between the primary module and the park brake module, often due to chafing or rodent damage
  4. A failed park brake module, though this is less common than wiring and power issues
  5. Low battery voltage or a weak battery that causes modules to drop offline intermittently
  6. Water intrusion into the park brake module connector or housing, leading to corrosion and communication loss
  7. A software or configuration mismatch in the park brake module after battery replacement or module service

How to diagnose and fix it

  1. Verify battery voltage and charge the battery if it is below 12.4 volts, as low voltage is a frequent cause of communication codes
  2. Check all fuses that supply power to the park brake module, including any underhood and interior fuse box locations
  3. Inspect the park brake module connector for corrosion, water intrusion, or loose pins, and clean or repair as needed
  4. Perform a voltage drop test on the ground circuit at the park brake module to confirm a solid ground connection
  5. Use a scan tool to check for communication with the park brake module; if it does not respond, proceed to CAN bus voltage and resistance testing
  6. Measure CAN bus voltages (typically around 2.5 volts on both lines with the key on) and check for opens or shorts in the wiring between modules
  7. If all power, ground, and wiring checks pass, substitute a known-good park brake module or perform module reprogramming per manufacturer procedures

What most technicians overlook on U0136

  • A weak or failing battery is a leading cause of U0136 because the park brake module may drop offline during cranking, setting the code without any hard wiring fault.
  • The park brake module often shares a power circuit with other chassis modules, so a blown fuse may disable multiple systems and set several U-codes at once.
  • Rodent damage to the CAN bus wiring near the park brake module is common in vehicles parked outdoors for extended periods, and the chewed insulation may not be visible without removing interior trim.
  • A U0136 code can be set by a module that is awake but not transmitting due to an internal fault, so a module that powers up does not guarantee it is communicating correctly.
  • After repairing the underlying fault, the code may remain stored until the module completes a full sleep-wake cycle, so clearing codes immediately may not be successful.

Can I keep driving with U0136?

The vehicle is generally safe to drive because the foundation brakes remain fully functional, but the electronic parking brake may not engage or release as expected. Avoid parking on steep inclines until the fault is repaired, and do not rely on the parking brake to hold the vehicle.

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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