U0139
UniversalLost Communication With Suspension Control Module B
The vehicle detected that communication with Suspension Control Module B was interrupted or unavailable. The module helps manage suspension functions where fitted, and other modules may rely on its messages. The cause could be a power, wiring, network, or module issue; this code alone does not prove the module needs replacement. Effects depend on the vehicle, and exact applicability and procedures depend on model, year, and engine.
⚠️ Before You Begin (Safety First)
If the vehicle’s ride height changes unexpectedly, handling becomes unstable, or a suspension warning appears with a noticeable change in control, stop somewhere safe and arrange professional assistance. If the vehicle handles normally, drive cautiously to a repair facility and avoid unnecessary trips until the fault is assessed.
Common Symptoms
- A suspension or chassis warning may appear if the vehicle reports that the module is unavailable.
- Suspension functions managed by the affected module may be limited, unavailable, or operating in a default mode, depending on the vehicle.
- Ride or handling may change if the unavailable communication affects suspension control.
- There may be no noticeable symptoms if the interruption is brief, intermittent, or does not affect a function the driver can readily feel.
Common Causes
- Loss of power or ground to Suspension Control Module B, such as from a fuse, connection, or wiring problem.
- Loose, damaged, corroded, or water-affected connectors or wiring between the module and the vehicle network.
- A communication network fault that prevents messages from reaching or leaving the module.
- A fault within Suspension Control Module B; this should be considered only after its power, ground, connections, and network path are checked.
- A temporary or intermittent electrical disturbance that interrupted communication.
Diagnostic Steps
- Note any suspension warnings and changes in ride height or handling; stop driving if control feels unsafe.
- Check the owner’s manual for suspension-related warnings and any vehicle-specific guidance.
- With the vehicle safely parked and the ignition off, visually inspect accessible wiring and connectors around the suspension system for obvious damage, looseness, or moisture. Do not unplug connectors with the ignition on.
- Check only fuses identified for suspension or control modules in the vehicle’s manual. Replace a blown fuse only with the specified type and rating; if it blows again, have the circuit diagnosed.
- If the warning remains or returns, arrange a scan of all modules. A code reader that accesses only the engine controller may not show the communication evidence needed to diagnose this fault.
When to Call a Professional
Scan all available modules and note which ones report communication faults, including whether the issue is current or intermittent. Use vehicle-specific service information to check the module’s power and ground, fuses, connectors, and network wiring. Confirm the network fault is resolved before considering module replacement; any required programming or setup depends on the vehicle.
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Commonly Asked Questions
Does U0139 prove that Suspension Control Module B has failed?
No. It reports lost communication, which can result from a power or ground problem, wiring or connector damage, a network fault, or a module fault. The communication path should be tested before replacing the module.
Can I drive with U0139?
It depends on whether the fault has affected suspension behavior. If ride height or handling changes, or the vehicle feels unstable, stop safely and arrange assistance. If it handles normally, drive cautiously to a repair facility.
Why might there be no symptoms?
The interruption may be intermittent, or the lost messages may not cause an obvious change in a function the driver can feel. A stored code can still help identify a communication problem that should be checked.
What should be checked before replacing a module?
A technician should scan all modules, check the affected module’s power and ground, inspect connectors and wiring, and test the communication network using vehicle-specific service information.
Browse Available Code Guides
Previous and next available guides in database record order, across makes. Adjacent entries may share a code number and do not necessarily describe related faults.