OBD-II trouble code
B003A: Second Row Right Frontal Stage 2 Deployment Control (Subfault)
The second firing stage of the second-row right frontal airbag is out of specification. The bag can still deploy — but only ever at the force reserved for a mild crash, which is why this fault gets deferred and why deferring it is expensive.
Quick facts
- System
- Body
- Category
- Airbag / SRS Restraints
- Severity
- High severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $120 – $1,000
- DIY difficulty
- Shop recommended
What does B003A mean?
B003A concerns the second of the firing stages in a multi-stage frontal airbag serving the right-hand second-row seat. The final character is a hexadecimal A, so B0039, B003A and B003B are consecutive codes describing stages one, two and three of the same device.
What separates a stage two fault from every other kind of restraints fault is that it degrades rather than disables. Stage one is the stage that always fires; if its loop is faulty there may be no useful deployment at all. Stage two exists so the module can add force when the crash is severe enough to warrant it. With stage two unavailable, the airbag still deploys and still protects an occupant in a minor impact — the system simply loses the ability to escalate. The shortfall therefore never appears in a fender-bender, never shows up in normal use, and only matters in precisely the severe collision the second stage was designed for. That combination makes it the restraints fault most likely to be put off, and the one where putting it off costs the most.
The diagnostic advantage of a per-stage code is real and worth using deliberately. Each stage has its own squib inside the inflator, its own pair of terminals in the connector, and its own resistance measurement taken independently by the module. So the pattern of codes is itself a test. A stage two fault with stage one reading healthy proves a great deal for free: the shared feed to the seat, the common ground, the long harness section running under the floor, the connector body, and the module's own supply are all demonstrably intact, because the healthy stage runs through every one of them. What is left is a very short list — the stage two squib itself, or the two terminals that serve it. Conversely, when all the stages for one inflator report faults together, nothing has been narrowed down and the shared path is where to look.
That distinction has a direct cost consequence, because inflators are not sold stage by stage. There is no such thing as a replacement stage two squib. Condemning it means buying the complete inflator or the entire seat-mounted assembly on the applications that use one, so the difference between a bent terminal and a failed squib is the difference between a small repair and a large bill. Proving which one you have — by inspecting and, where the manufacturer permits, testing the individual terminals before ordering anything — is one of the more worthwhile hours in restraints diagnosis.
One caution specific to the position: frontal airbags for rear seating are uncommon, so before any of this applies, confirm the vehicle actually has one at the second-row right seat rather than trusting a generic code description.
The car drives normally throughout. Deployment loops carry live pyrotechnics and are measured with current-limited tooling only, after the system has been powered down to the manufacturer's procedure.
Common causes
- Open or out-of-specification stage two squib inside the second-row right inflator
- Bent, spread or corroded terminal serving the stage two pair specifically, with the stage one pair unaffected
- Connector partially seated so one terminal pair makes contact and the other does not
- Damage to the loop during child-seat installation or repeated folding of the kerb-side seat
- Incorrect inflator fitted after a previous deployment, with a stage two resistance the module does not expect
- Restraints module configuration expecting a multi-stage inflator the vehicle was not built with
- Corrosion in the under-seat connector after a spill in the rear footwell
- Harness damage under the seat from cargo, seat rails or child-restraint hardware
- Failed stage two output in the restraints control module, confirmed only after everything external is cleared
Symptoms
- Airbag warning lamp on and staying on
- B003A stored with a symptom byte describing the exact circuit condition
- Stage one loop reporting healthy while stage two does not
- Code returning immediately after every clearing attempt
- Fault present since a previous airbag deployment and repair
- Fault that changes state as the second-row right seat is folded or the connector is disturbed
- No warning of any kind while driving, and no change in vehicle behaviour
- Nothing an occupant would notice until a severe collision
Diagnostic steps
- 1.Confirm the vehicle is actually fitted with a frontal airbag at the second-row right position, which is uncommon hardware, before treating the code as a wiring fault.
- 2.Record which stage codes are present. Stage two alone with a healthy stage one proves the shared feed, ground, harness run, connector body and module supply are all good, and narrows the fault to the stage two squib or its two terminals.
- 3.If every stage for this inflator reports a fault, redirect entirely to the shared path — connector, ground and harness — rather than suspecting multiple squibs.
- 4.Capture the full symptom byte, since open, shorted-high and shorted-low lead to different places even within that short list.
- 5.Power down and discharge the restraints system to the manufacturer's procedure before opening any connector.
- 6.Inspect the connector under strong light for a partially seated housing and for bent, spread or corroded terminals on the stage two pair specifically.
- 7.Check the inflator part number against what the module expects, particularly on a vehicle with any deployment history.
- 8.Measure each stage loop separately with approved current-limited equipment and compare both against specification, so the healthy channel serves as a same-vehicle reference.
- 9.Prove the terminal before condemning the squib, because an inflator is not sold by the stage and the cost difference is substantial.
- 10.After repair, clear the codes, run the self-test and confirm both stage loops report healthy over several ignition cycles.
Repair cost
$120 – $1,000
A partially seated connector or a single repaired terminal is the inexpensive outcome at $150 to $380, and it is worth spending diagnostic time to establish whether that is what you have. There is no such thing as a stage two squib sold on its own, so condemning it means the whole inflator or seat-mounted assembly — $300 to $800 in parts on the applications that use one, plus fitting. Restraints module replacement with programming reaches $1,000. Diagnosis is $110 to $220 and is the best-value hour on this code, because the gap between a terminal repair and an inflator is several hundred dollars and only testing separates them.
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. It typically involves emissions-critical components, refrigerant handling, or other work that requires manufacturer-grade tooling, training, or certification. DIY attempts often produce a more expensive problem than the original code.