Longitudinal Acceleration Sensor Circuit Malfunction
What does C0139 mean?
The C0139 code means the vehicle's onboard diagnostic system has detected: Longitudinal Acceleration Sensor Circuit Malfunction. This is a moderate severity code.
Common Symptoms
- Stability control warning on
- Hill descent control disabled
- Brake assist not functioning optimally
- ESC fault message
- Dynamic traction control inactive
Probable Causes (Ranked by Likelihood)
- Failed longitudinal acceleration sensor Very High
- Sensor mounting shifted or loose High
- Corroded sensor wiring connector Moderate
- ESC module sensor processing fault Low
Step-by-Step Diagnostic Procedure
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Scan ESC module for longitudinal acceleration DTCs
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Read sensor data on level surface at rest and during braking
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Check sensor mounting for secure attachment
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Inspect connector and wiring for damage
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Compare readings to specifications
Frequently Asked Questions
What is a longitudinal acceleration sensor?
It measures the forward and backward forces on the vehicle during acceleration and braking. This data helps the ESC system manage hill descent control and brake force distribution.
Is this sensor found on all vehicles?
Not all vehicles have a dedicated longitudinal sensor. Many combine yaw rate, lateral, and longitudinal sensing into a single inertial measurement unit or sensor cluster.
Does this affect hill descent control?
Yes. Hill descent control relies on the longitudinal sensor to measure the vehicle pitch angle and rate of descent. Without valid data, the system will disable itself.