OBD-II trouble code
B0013: Passenger Knee Bolster Deployment Control (Subfault)
An electrical fault in the passenger knee airbag firing loop. It is the lowest restraint connector in the vehicle and the only one at foot height, which makes footwell water, kick damage and trim work the causes worth checking before the airbag itself.
Quick facts
- System
- Body
- Category
- Airbag / SRS Restraints
- Severity
- High severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $100 – $900
- DIY difficulty
- Shop recommended
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What does B0013 mean?
B0013 is stored by the restraints control module when the firing loop for the passenger-side knee airbag falls outside the resistance window a pyrotechnic circuit must hold. A symptom byte identifies whether the module saw an open, a short, or a value simply out of range.
What the knee airbag does is worth understanding, because it is not the cushion people assume it is. Its function is geometric. In a frontal impact the occupant's pelvis tends to slide forward and downward under the lap belt — submarining — which changes where the upper body ends up and therefore how it meets the frontal airbag. The knee bag deploys from the lower dash to catch the knees early, hold the pelvis where the belt can restrain it, and control the angle at which the torso arrives. That means a knee airbag fault degrades how well the frontal airbag works, even though the frontal bag itself is perfectly healthy. It is a supporting device, and the support is what is missing.
The practical distinguishing feature of this code is where the connector lives. The knee airbag mounts at the very bottom of the dash and its loop terminates behind the lower trim panel, lower than any other restraint connector in the vehicle. Note what that does and does not imply about accessory work. The interior fuse panel and the diagnostic connector are on the driver's side of the dash on most vehicles — the diagnostic socket is required to be reachable from the driver's seat — so the cavity that dashcam kits, remote starters, alarms and trackers are usually wired into is the driver's, not this one. Where it matters here is that reaching the passenger lower dash means flexing or dropping the same panel this loop terminates behind: glovebox and kick-panel work, amplifier and subwoofer feeds taken down the passenger side, cabin filter access on the vehicles that put it there, and any job that needs the passenger footwell trim out. Establish which side of the dash the recent work was actually on before treating an accessory installation as the cause.
The footwell environment adds the rest of the cause list. This is the lowest airbag in the vehicle and the only one at foot height, so it takes kicks from passengers, and it sits where wet shoes, snow and rain-soaked floor mats put moisture. Stacked or aftermarket floor mats are a specific hazard because they raise the footwell surface toward the connector and hold water against it.
One more point specific to this position: on many vehicles the knee bolster panel itself is a structural, energy-absorbing component rather than trim, and the airbag deploys against it in a designed direction. A panel replaced with a wrong or damaged part, or refitted with missing fasteners after accessory work, is worth noticing while the trim is off.
The vehicle drives normally. The system must be powered down per the service procedure before anything here is disturbed.
Common causes
- Corroded or backed-out terminal in a connector sitting at footwell height
- Moisture from wet shoes, snow or saturated floor mats reaching the connector
- Stacked or aftermarket floor mats holding water against the lower dash area
- Kick damage to the connector or its harness from passenger foot traffic
- Connector disturbed during work behind the passenger lower dash — glovebox or kick-panel removal, a passenger-side accessory feed, footwell trim out for carpet or filter access
- Damaged wiring in the firing loop where it runs down the lower dash
- Failed inflator squib in the knee airbag assembly
- Knee bolster panel refitted incorrectly or with missing fasteners after previous work
- Faulty restraints control module, which should be concluded last
Symptoms
- Airbag / SRS warning light on with the vehicle driving normally
- Stored B0013 with a symptom byte in the restraints module
- Fault appearing within days of work behind the passenger lower dash, such as a glovebox, kick-panel or passenger-side accessory job
- Lower dash panel that sits loose, rattles, or has missing fasteners
- Fault that came on after winter driving or after the footwell got wet
- Companion passenger-side restraint codes stored alongside it
- Intermittent airbag lamp that responds to footwell movement
- No effect on engine or driving performance
Diagnostic steps
- 1.Read the code with its full symptom byte and note any companion restraint codes before anything is disturbed.
- 2.Ask what has been done behind the passenger lower dash recently — glovebox or kick-panel removal, a passenger-side accessory feed, footwell trim out for carpet or cabin filter work — and establish which side of the dash it was on, since the interior fuse panel and diagnostic socket most accessories tap are on the driver's side.
- 3.With the restraint system safely disabled per the service procedure, remove the lower dash panel and inspect the knee airbag connector for a disturbed latch, backed-out terminals and added wiring taped into the loom.
- 4.Follow the routing of any added wiring that runs down the passenger side, since a cable tie or a routed feed pressing on the SRS connector is enough to unseat it.
- 5.Inspect for moisture, corrosion and water staining at footwell height, and check whether floor mats are stacked or aftermarket.
- 6.Check the connector's shorting bar, which should hold the loop shorted whenever the airbag is unplugged.
- 7.Measure the deployment loop resistance against the manufacturer's specification with approved current-limited restraints test equipment only, never with a general-purpose multimeter — an ordinary meter can pass enough current through a live pyrotechnic circuit to initiate it.
- 8.While the panel is off, confirm the knee bolster panel itself is the correct part, undamaged and fully fastened, since the airbag deploys against it in a designed direction.
- 9.If the airbag or module has been replaced previously, verify the part number and that any required configuration was carried out.
- 10.After repair, clear the codes, refit the panel fully, and confirm the airbag lamp completes its bulb check and stays out.
Repair cost
$100 – $900
This is generally the least expensive of the frontal-family deployment loops to work on, because the lower dash panel drops out easily and the connector is reachable without dismantling the dash. A reseated or repaired connector runs $150 to $320 including SRS diagnostic time, and where an accessory installation is the cause that is the usual outcome. A replacement knee airbag assembly is typically $250 to $600 for the part, fitted, which is well below a frontal airbag module. SRS diagnostic time runs $100 to $200. Costs reach the top of the range only where the restraints module itself is implicated and needs replacement with programming.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with airbag control module (sdm) replacement / reset preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
Leave this one to a qualified shop. The barrier here is live pyrotechnic devices, which must be powered down and allowed to discharge before a connector is touched, and which are tested only with equipment approved for restraints work. DIY attempts often produce a more expensive problem than the original code.