B1620: How to Diagnose & Fix — Airbag System Control Module (SRSCM) Internal Fault
3 vehicles · 2 makes · $250-$2,400 repair
How to diagnose and fix B1620: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Hyundai Accent · 2006–2017
The occupant classification sensor mat built into the front passenger seat cushion fails internally - the printed pressure-sensing traces crack with repeated loading. The car then either lights the SRS/airbag warning lamp with an OCS fault stored, or leaves the PASSENGER AIRBAG OFF indicator lit with an adult sitting in the seat, meaning the passenger airbag will not deploy in a crash. It affects MC (2006-2011) Accents heavily and continues on later cars, and it is well documented across Hyundai/Kia models generally. The financial sting is that Hyundai does not sell the mat separately - the fix is the entire lower seat cushion assembly, and forum owners have posted dealer quotes in the $1,200-$2,400 range for what is a failed sensor pad.
Common Symptoms
- SRS/airbag warning light stays on
- PASSENGER AIRBAG OFF light stays lit with an adult in the seat
- Airbag light comes on only when someone sits in the passenger seat
- Intermittent light that changes with seat load
How to Fix
Pull the SRS codes with a scanner that reads airbag modules (a generic OBD-II reader will not show them). First inspect the connectors under the passenger seat for corrosion, a partially seated plug, or a chafed harness from the seat rails - loose connections cause the same fault and cost nothing. If the mat itself is bad, the OEM route is a passenger seat cushion assembly replacement plus an OCS calibration/zeroing procedure at the dealer. Far cheaper alternatives owners use: an aftermarket replacement sensor mat/bypass emulator, or sending the seat cushion out to a sensor rebuild service. After any repair the OCS system must be recalibrated or the light returns.
Sources for this issue (3)
Kia Telluride · 2023–2023
On certain 2023 Tellurides the wire harnesses that feed the second-row seat-mounted side air bags can be damaged during seat travel or assembly routing. A damaged harness opens or shorts the squib circuit, so the second-row side air bag will not deploy in a side impact — the occupants who most need that bag (rear passengers, often children in boosters) lose their protection. The defect frequently announces itself as an air bag warning lamp, though the recall population was defined by build data, not by whether the lamp had come on yet. This is distinct from the front seat-back frame recall on 2025 vehicles.
Common Symptoms
- Air bag / SRS warning light illuminated on the cluster
- Second-row side air bag fault stored in the SRS module
- Warning appears after second-row seats have been slid or folded repeatedly
How to Fix
Free recall repair under NHTSA 23V035: dealers inspect the second-row side air bag wire harnesses and repair or replace any damaged harness. If the air bag warning light is on, do not defer — the SRS is fully or partially disabled in the meantime. Have the stored SRS codes read before the visit so the dealer can document the open circuit.
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Sources for this issue (1)
Kia Forte · 2010–2018
Two Kia safety recalls match this page’s retained year groups. Under 18V363000 (SC165), the airbag control unit in certain 2010-2013 Forte vehicles can suffer electrical overstress during a frontal crash, preventing the frontal airbags and seatbelt pretensioners from deploying. Under 22V031000 (SC226), the ACU cover in certain 2017-2018 Forte vehicles can contact a memory chip, illuminate the airbag warning light with DTC B1620 and deactivate the airbags.
Common Symptoms
- Airbag warning light remains illuminated
- DTC B1620 on later recall population
- Airbags or pretensioners may not deploy in a crash
How to Fix
Check the VIN for both recalls. For 18V363000, Kia installs an extension wire-harness kit between the ACU and vehicle harness. For 22V031000, Kia updates ACU software when B1620 is absent and replaces the ACU when B1620 is present. Both remedies are free and VIN-specific. No retail airbag-control part should be purchased from this page. If the airbag warning light stays on, follow Kia’s recall instructions and arrange dealer diagnosis.
Sources for this issue (4)
Find B1620 by make
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B1620 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does B1620 mean?
B1620 stands for "Airbag System Control Module (SRSCM) Internal Fault." The Airbag Control Unit runs a self-diagnostic routine for roughly six seconds after the ignition is turned on. B1620 sets when that self-test reports an internal failure of the module itself. Hyundai has issued two separate remedies over time: Service Campaign TX8 reprograms the ACU because sufficient vibration during the diagnostic window (for example a door being slammed) could cause the module to erroneously detect an internal fault; Warranty Extension TXXQ / TSB 24-BE-014H lists B1620 as a genuine internal-failure code requiring ACU replacement on Accent (HC).
What are the most common causes of B1620?
The most common causes of B1620 are: Genuine internal electronic failure of the ACU/SRSCM (remedy: ACU replacement per Warranty Extension TXXQ), Outdated B1620 diagnostic logic — vibration such as a slammed door during the post-ignition self-test falsely sets the code (remedy: ACU reprogramming per Service Campaign TX8), Water intrusion at the module location shorting the board, Low or unstable supply voltage to the ACU during the self-test. The specific cause varies by vehicle.
How much does it cost to fix B1620?
Repair costs for B1620 range from $250 to $2,400, depending on the vehicle and root cause.
Which vehicles are affected by B1620?
Au7o has documented B1620 across 3 vehicle models from 2 manufacturers: Hyundai, Kia.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.