B1620 – Internal fault – Replace supplemental restraints system control module (SRSCM) (Kia)

Kia-specific code — factory diagnostic data

B1620 means the Kia EV6 airbag system has detected an internal problem in the Supplemental Restraints System Control Module (SRSCM). In plain terms, the SRS warning light will likely stay on and the airbags may not protect you as designed. This is a Kia manufacturer-specific body/SRS code, and the exact logic behind it can vary by platform. According to Kia factory diagnostic data, this code indicates an “Internal fault – Replace supplemental restraints system control module (SRSCM).” Treat that wording as a suspected trouble area, not a guaranteed bad module. You must follow OEM SRS depowering steps before touching any SRS connector.

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B1620 Quick Answer

B1620 on a Kia EV6 points to an internal fault detected by the SRSCM (airbag control unit). Verify SRSCM power, grounds, and network integrity first, because wiring or voltage events can mimic an internal fault.

What Does B1620 Mean?

Official meaning (Kia-defined): B1620 – Internal fault – Replace supplemental restraints system control module (SRSCM). The AB (Airbag) module stores this DTC when it decides its internal operation cannot be trusted. In practice, the system will often disable some or all restraint functions and command the SRS warning lamp on.

What the module actually checks: The SRSCM runs self-tests on its processor logic, internal memory, and internal sensor processing. It also monitors its power supply stability and basic communication behavior. Why that matters: a low-voltage event, poor ground, water intrusion, or network disruption can cause self-test failures. Those external issues can set B1620 even when the SRSCM hardware remains functional.

Theory of Operation

Under normal conditions, the SRSCM continuously monitors crash inputs and system health. It supervises igniter circuits, impact sensing, and warning lamp commands. The module also communicates with other vehicle modules over the network to share restraint status and receive needed information. The EV6 uses this supervision to keep the system armed and ready without false deployments.

B1620 sets when the SRSCM detects a self-test result outside its allowed range. The failure can come from internal electronics or from unstable external conditions. Power or ground interruptions can corrupt internal checks and trigger an internal-fault decision. Network problems can also create timing and plausibility errors that push the module into a fault state. Because SRS work carries deployment risk, only use OEM-approved test methods and depower the SRS before any connector handling.

Symptoms

You will usually notice an SRS warning and loss of normal restraint readiness.

• SRS light stays on or returns soon after a key cycle
• Airbag message warning displayed in the cluster, if equipped
• Stored AB code B1620 present as current or history in the Airbag module
• Readiness change restraints may show “disabled” or “service required” status
• Intermittent faults warning appears after bumps, moisture, or voltage dips
• Other SRS DTCs additional internal, undervoltage, or communication-related codes may accompany B1620

Common Causes

• SRSCM internal memory fault: Non-volatile memory corruption can make the AB (Airbag) module fail its self-check and log B1620.
• Low battery voltage during crank or wake-up: A voltage dip can interrupt the SRSCM boot sequence and trigger an internal fault decision.
• High-resistance power feed to the SRSCM: Corroded fuse contacts or a loose junction can drop voltage under load and mimic a failing module.
• High-resistance ground path at the SRSCM: A weak ground can pass a continuity test yet fail voltage-drop under load, leading to internal reset events.
• Intermittent connector contact at the SRSCM: Terminal fretting or poor pin tension can create brief opens that look like an internal controller failure.
• Water intrusion or condensation at the SRS module area: Moisture can create leakage paths and corrosion that disrupt internal reference circuits and self-tests.
• Wiring harness damage near the AB module: Pinched or chafed wiring can cause momentary power loss or noise that the SRSCM flags as an internal fault.
• Aftermarket electrical equipment causing EMI or backfeed: Poorly integrated accessories can inject noise or voltage into shared circuits and upset SRSCM logic.

Diagnosis Steps

Use a scan tool with full Kia SRS access, plus a DMM and a low-amp clamp. Follow Kia SRS depowering procedures before touching any SRS connector. Use only OEM-approved back-probing and breakout methods. Avoid standard test leads on SRS circuits. Plan to verify power and ground with voltage-drop under load, not continuity alone.

1. Confirm B1620 in the AB (Airbag) module and document code status. Record freeze frame or event data, focusing on battery voltage, ignition state, and any reset or undervoltage flags. Note related SRS or power supply DTCs. Freeze frame shows conditions when the fault set. A scan tool snapshot can capture live voltage drops during a repeat test.
2. Perform a complete visual inspection of the power distribution path before any meter work. Check battery terminals, main fuses, and SRS-related fuses for looseness, heat discoloration, or corrosion. Inspect nearby harness routing for pinch points and abrasion. Do not disconnect SRS connectors until you depower the system.
3. Verify the scan tool can communicate reliably with the AB (Airbag) module. If communication drops, treat it as a power or ground integrity problem first. Confirm other modules report normal system voltage. An internal fault code often returns immediately at key-on if the issue is hard.
4. Depower the SRS system using Kia’s OEM procedure and required wait time. Then access the SRSCM area and inspect for signs of moisture, impact damage, or aftermarket wiring. Look for water tracks, damp carpet, or corrosion on brackets and fasteners. Restore power only after you re-secure connectors and confirm safe conditions.
5. Check all SRS-related fuses with a loaded method, not just an ohmmeter. Use a fused test light or an approved load tool to verify each fuse carries current. A fuse can test good for continuity yet fail under load at its blades or in the fuse box sockets.
6. Verify SRSCM power and ground integrity with voltage-drop testing under load. Back-probe using OEM-approved methods and keep SRS circuits undisturbed. With the circuit operating, measure voltage drop from battery positive to the SRSCM power feed. Then measure from SRSCM ground to battery negative. Accept less than 0.1V drop on grounds under load.
7. Inspect the SRSCM connector(s) and terminals after depowering the SRS again. Check for bent pins, spread terminals, corrosion, or partial backing-out. Confirm CPA locks and connector latches fully seat. Terminal fit problems can create millisecond opens that set internal fault logic.
8. Perform harness integrity checks on the SRSCM power and ground circuits. Use a wiggle test while monitoring scan tool data for voltage, reset counters, or module status changes. If your scan tool supports it, log a snapshot during a controlled road test. Snapshot captures intermittent faults that freeze frame cannot.
9. Check for conditions that commonly cause repeated SRSCM resets. Verify charging system stability and check for excessive ripple with OEM-approved methods. Inspect for aftermarket accessories tied into ignition feeds or grounds near the SRS module. Remove or isolate suspect equipment before condemning the SRSCM.
10. After you correct any power, ground, connector, moisture, or harness issues, clear SRS codes with a capable scan tool and run the Kia SRS self-check. Cycle ignition and re-scan to confirm B1620 does not return. If B1620 returns with verified power and ground, treat SRSCM internal fault as the most likely direction and follow Kia replacement and configuration procedures.

Professional tip: B1620 reads like “replace the module,” but SAE J2012 guidance still applies. The DTC message points to a suspect area, not a confirmed part. On the Kia EV6, prove stable SRSCM power and ground under load first. Most “internal” codes become repeatable only after you reproduce a reset or voltage sag.

Possible Fixes

• Clean and tighten battery and main power connections: Restore stable system voltage so the SRSCM completes self-tests without resets.
• Repair fuse box or power feed faults: Replace heat-damaged fuse sockets, repair loose junctions, or correct poor contact that fails under load.
• Repair ground path issues: Clean and re-secure SRSCM ground points and correct high voltage-drop conditions found during loaded testing.
• Connector/terminal service at the SRSCM: Correct pin fit, corrosion, or backing-out using OEM terminal repair methods and parts.
• Harness repair and re-route: Repair chafed or pinched wiring and secure routing to prevent intermittent opens or noise.
• Address water intrusion: Dry the area, repair the leak source, and replace corroded terminals or connectors as needed.
• SRSCM replacement and setup only after verification: Replace the SRS control module only after you confirm proper power, ground, and connector integrity, then perform required coding/initialization and post-repair checks.

Can I Still Drive With B1620?

You can usually drive the Kia EV6 with B1620 because it does not control propulsion. Treat it as a safety-critical condition anyway. B1620 comes from the AB (Airbag) system and points to an internal SRSCM fault area. That warning means the supplemental restraint system may not respond correctly in a crash. Do not let anyone work around SRS connectors or harnesses without depowering the SRS using Kia procedures. Avoid DIY electrical testing at the airbag module. Do not probe SRS circuits with standard test leads. Schedule proper diagnosis with a scan tool that supports full Kia SRS functions.

How Serious Is This Code?

This code carries high safety severity. It mainly becomes an “inconvenience” only in one sense. The vehicle may drive normally, but the SRS may not protect occupants as designed. An internal-fault message does not prove the SRSCM failed, per SAE J2012-DA guidance. It does tell you the module detected a self-check problem. A trained technician must confirm power, grounds, and network integrity before any module decision. Use only OEM-approved SRS test methods. SRS diagnosis requires SRS-capable scan equipment and proper training. Do not attempt repairs without those resources.

Common Misdiagnoses

Technicians often replace the SRSCM too early because the scan text says “replace.” That wastes money when a power feed, ground path, or connector issue caused the internal fault flag. Another common miss involves low system voltage history. A weak 12V battery or poor charging can corrupt SRS self-tests and set B1620. Some shops also skip AB module communication checks and DTC history. They clear codes and call it fixed. That approach hides an intermittent fault and resets valuable freeze data. Avoid backprobing SRS connectors with regular pins. Use OEM-approved breakout methods and follow Kia depowering steps first.

Most Likely Fix

The most common confirmed repair directions fall into two buckets. First, restore correct SRSCM power and ground integrity. That includes connector seating, terminal tension, corrosion removal, and voltage-drop testing under load at the AB (Airbag) module feeds. Second, if power, grounds, and network lines check good and B1620 resets after correct verification steps, the SRSCM may need replacement with Kia-specific programming and configuration. Do not treat replacement as automatic. Confirm the fault returns without harness disturbance and confirm the scan tool reports normal communication and stable supply data during the event.

Repair Costs

SRS/airbag repair costs vary significantly by component. Diagnosis must be performed by a qualified technician with SRS-capable equipment. Do not attempt airbag system repairs without proper training and safety procedures.

Last updated: April 10, 2026

Definition source: Kia factory description · Autel MaxiSys Ultra & EV. Diagnostic guidance is based on factory-defined fault logic for this code.