Airbags

B009A — Left Side Restraints Sensor 4 Circuit Fault (Subfault)

Severity: medium Safe to drive

What B009A means

The supplemental restraint system (SRS) control module constantly monitors its crash sensors and the circuits that connect them. B009A means it found a problem in the left side restraints sensor 4 circuit, such as an open, short, poor connection or implausible signal. As this is a subfault, an SRS-capable scan tool is needed to see the details.

Symptoms

  • SRS or airbag warning light on
  • Light stays on after the self-test at startup
  • Some airbags or pretensioners may be disabled
  • Code returns after being cleared

Possible causes

  1. Faulty left side restraints sensor 4
  2. Open or shorted wiring to the sensor
  3. Corroded or loose connector
  4. Wiring damaged during body work or seat or trim removal
  5. Faulty SRS control module (less likely)

How to diagnose

  1. Scan all modules with an SRS-capable tool and note the subfault data
  2. Inspect the sensor, harness and connector for damage, moisture and corrosion
  3. Check that connectors are fully seated, especially after recent interior or body work
  4. Disconnect the battery and wait as the manufacturer specifies, then test circuit resistance and shorts to ground and power
  5. Compare sensor readings to specification, or swap in a known good sensor if possible
  6. Clear the code and see if it returns; if so, suspect the SRS module

Common fixes

  • Clean the connector and restore good contact
  • Repair or replace the damaged wiring harness
  • Replace left side restraints sensor 4
  • Replace or reprogram the SRS control module if confirmed faulty

Questions and answers

Can I drive with code B009A?

Yes, the car will drive normally because the code does not affect the engine or brakes. However, side crash protection may be reduced, so get it diagnosed soon.

Can I test SRS circuits myself?

Reading codes and visually inspecting connectors is safe. Only work on airbag circuits with the battery disconnected and by following the manufacturer's procedure, or an airbag could deploy.

Why did B009A appear after a repair?

A common cause is a connector left loose or a harness pinched under the seat, in the pillar or in the door. Recheck the areas that were worked on.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.