B1620 on Hyundai: How to Diagnose & Fix
Airbag System Control Module (SRSCM) Internal Fault
1 Hyundai model · 1 documented issue · 1 critical · $250-$2,400 repair
B1620 on Hyundai by model: symptoms, diagnosis and fix
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)
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 on a Hyundai?
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). On Hyundai it is documented across 1 model: Accent.
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 on a Hyundai?
Published repair estimates on Hyundai range from $250 to $2,400 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for B1620 on a different make?
View B1620 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.