B29C1 – Airbag crash output line error (Kia)

B29C1 means your 2025 Kia EV3 has logged an SRS fault that can disable some or all airbag functions. For most owners, the real-world effect is an airbag warning lamp and reduced crash protection until repairs finish. According to Kia factory diagnostic data, this code indicates an “Airbag crash output line error.” That wording points to a problem with the SRS module’s crash output line circuit, not a guaranteed bad airbag. Because this involves the Supplemental Restraint System, follow Kia SRS depowering procedures before touching any related connector. Use only OEM-approved test methods and an SRS-capable scan tool.

B29C1 Quick Answer

B29C1 on Kia means the SRS detected an error on the “crash output line” circuit. Treat it as a safety-critical wiring or module output integrity fault until you prove the root cause.

What Does B29C1 Mean?

Official definition: “Airbag crash output line error.” In plain terms, the airbag control system does not like what it sees on a dedicated crash output line. In practice, the SRS turns on the airbag warning light and may inhibit some deployment logic or related crash notification functions as a precaution.

What the module checks and why it matters: The SRS control module monitors the crash output line for electrical plausibility. It checks for conditions like an open, short, or an out-of-range load on that line. The module uses this feedback to confirm it can command and report crash-related outputs correctly. That matters because you must verify circuit integrity first. The DTC only identifies a suspected trouble area, not a failed part.

Theory of Operation

On Kia vehicles, the SRS control module manages airbags and seat belt pretensioners. It also manages crash-related outputs used for safety coordination. Those outputs can trigger other actions, depending on platform design. Examples include hazard activation requests, event notifications, or other crash-related interlocks.

With B29C1, the SRS module expects the crash output line to behave like a healthy electrical circuit. Damage, corrosion, poor terminal tension, or an incorrect load can change the line’s electrical characteristics. The module flags an error when the feedback does not match its internal checks. This code guides you to test the output line circuit end-to-end using Kia-approved methods.

Symptoms

You will usually notice an SRS warning first, then scan tool clues during diagnosis.

• Airbag light illuminated on the cluster (SRS/MIL for restraint system)
• Message warning about airbag or safety system fault on the display
• Stored DTC B29C1 in the SRS/airbag module with a current or history status
• Limited SRS function with inhibited readiness until the fault no longer reports
• Intermittent fault that appears after seat movement, vibration, or recent body work
• Post-repair occurrence after collision repair, bumper work, dash work, or harness service
• Freeze frame clues showing the fault occurred during key-on checks or while driving

Common Causes

• Open circuit in the crash output line: A broken wire or separated terminal stops the SRS module from driving or monitoring the crash output circuit.
• High resistance from corrosion or fretting: Corrosion at a connector adds resistance and distorts the crash output line’s expected electrical response.
• Short to ground on the crash output line: Chafed insulation can ground the line and pull the signal low outside the module’s plausibility checks.
• Short to power/voltage feed: Contact with a power source can hold the line high and trigger an output line error during self-checks.
• Poor terminal tension or partial connector seating: A connector that “clicks” but does not fully lock can create intermittent opens that set B29C1 on key cycles.
• Harness damage near the SRS module or along the body routing: Pinched or stretched wiring after interior work can deform conductors and create intermittent faults.
• Incorrect repair method on an SRS-related circuit: Non-OEM splices, wrong terminals, or probing damage can change circuit impedance and cause monitoring errors.
• Internal fault in the SRS control module output driver: A failed driver or internal monitoring circuit can report an output line error after you verify the external circuit integrity.

Diagnosis Steps

Use a scan tool with full Kia SRS access, not a generic OBD reader. Gather Kia service information and approved SRS depowering steps. Use a DMM with min/max and voltage-drop capability. Use only OEM-approved SRS test adapters and back-probing methods. Avoid standard test lights and piercing probes on SRS circuits.

1. Connect the SRS-capable scan tool and run a full vehicle scan. Record B29C1 as stored, confirmed, or history. Save freeze frame for B29C1 and note battery voltage, ignition state, and any related SRS, body, or power supply DTCs. Freeze frame shows conditions when the code set. Use a scan tool snapshot later to catch intermittents during a wiggle test.
2. Perform SRS-safe prep before any physical inspection. Depower the SRS using Kia’s procedure and wait the specified time before touching connectors. Then do a visual inspection of the crash output line routing you can access without unplugging yellow SRS connectors. Look for recent interior work, pinched harnesses, water tracks, or abrasion points.
3. Check fuses and power distribution that feed the SRS system before any module measurements. Verify each related fuse has the correct supply on both sides under load. Use a voltage-drop method across suspect fuse contacts and fuse box terminals while the circuit powers up. A fuse can look good and still fail under load due to heat damage.
4. Verify SRS module power and ground integrity under load after you follow the safe test setup in Kia service information. Use voltage-drop testing, not continuity alone. Measure ground drop with the circuit operating and confirm less than 0.1 V drop. Then check the power feed drop from the fuse output to the module feed under load. Poor feeds can cause false “output line” errors during self-tests.
5. With SRS depowered, inspect the SRS module connector area and the specific crash output line terminals referenced by Kia service information. Check for pushed-out pins, bent terminals, moisture, and terminal spread. Confirm connector locks and secondary locks fully seat. Do not force terminals with picks that can damage plating or tension.
6. Test the crash output line for opens and shorts using OEM-approved methods. Keep the SRS module disconnected when the service procedure calls for it. Check for short to ground and short to power on the line from the module side to the harness side. Next, verify end-to-end continuity only after you rule out shorts. Do not use a powered test light on SRS wiring.
7. If Kia procedures allow, perform a controlled wiggle test while monitoring the scan tool for B29C1 status and any relevant SRS data PIDs. Focus on known stress points such as kick panels, A-pillar routes, under-seat paths, and areas near body seams. Use a scan tool snapshot to capture live data when the fault occurs. An intermittent open often shows up as a momentary state change before the code resets.
8. Check for evidence of incorrect prior repairs. Look for aftermarket splices, twisted-and-taped joints, non-OEM terminals, or incorrect connector housings in the crash output line path. Repair wiring using OEM-approved terminals, crimp tools, and splice methods only. SRS monitoring reacts to impedance changes from poor repairs.
9. After repairs, restore connectors, confirm routing and strain relief, then repower the SRS using Kia’s procedure. Clear codes with the SRS-capable scan tool only after you complete reassembly. Cycle ignition and re-scan to confirm B29C1 does not return. A hard fault commonly returns immediately at key-on because the SRS runs self-checks every cycle.
10. If you verify power, ground, and the crash output line circuit integrity, follow Kia pinpoint tests for the SRS module output driver. Confirm you did not miss an intermittent terminal fit issue. Only then consider module-level faults and required programming steps. Document every measurement before any module replacement decision.

Professional tip: Treat B29C1 as a suspected circuit area, not a failed part. The SRS module monitors output lines with internal diagnostics that can flag marginal resistance. Voltage-drop testing on feeds and grounds catches the most missed causes. Terminal tension problems also create “perfect” continuity readings with the connector unplugged.

Possible Fixes

• Repair an open, short, or high-resistance section of the crash output line: Restore correct wiring integrity using OEM-approved terminals and splice practices.
• Clean and correct connector issues: Remove moisture sources, correct pushed pins, and restore proper terminal tension and connector seating.
• Correct SRS power or ground faults: Repair fuse box terminal heat damage, ground points, or power feed resistance found by voltage-drop tests.
• Repair harness routing and protection: Re-route away from pinch points, replace damaged loom, and restore strain relief to prevent repeat failures.
• Replace and program the SRS control module only after circuit proof: Do this only when Kia pinpoint tests confirm an internal output driver or monitoring fault.

Can I Still Drive With B29C1?

You can usually drive a 2025 Kia EV3 with B29C1, but you should treat it as a safety-critical warning. This DTC means the airbag system reports a crash output line error. That line supports crash communication and deployment strategy. When the SRS module flags this fault, the system may disable part of the restraint strategy. The vehicle will still move normally, but your supplemental restraint protection may not work as designed in a collision. Do not ignore an airbag warning lamp. Do not try DIY probing on SRS wiring. Schedule diagnosis soon with a scan tool that fully supports Kia SRS functions.

How Serious Is This Code?

B29C1 ranks as high severity because it involves the SRS crash output line. In the best case, the fault comes from a poor connector fit or harness strain. That situation still compromises airbag readiness until you correct it. In worse cases, the SRS module cannot confirm crash output line integrity, so it may inhibit airbags, pretensioners, or crash signaling. This code rarely affects drivability, charging, or EV power delivery. It directly affects occupant protection. Diagnosis requires strict SRS depowering steps, OEM-approved test methods, and trained handling. Do not attempt home repairs on SRS circuits.

Common Misdiagnoses

Technicians often replace SRS components too early with B29C1. The most common mistake involves condemning the airbag control module without proving the crash output line circuit fault. Another frequent error involves checking continuity with standard test leads or powered test lights. That can damage SRS circuits or trigger additional faults. Some shops also chase “crash data” assumptions and skip basic power and ground checks. A loose ground or water intrusion at a connector can mimic a line error. Avoid wasted spending by verifying connector pin tension, corrosion, harness routing damage, and module power and ground integrity before any parts decisions.

Most Likely Fix

The most common confirmed repair direction involves restoring circuit integrity on the crash output line path. That usually means repairing an open, short, or high resistance caused by harness damage or connector corrosion. A second frequent direction involves correcting a poor connection at an SRS-related connector after prior body or interior work. Do not treat these as certain fixes. Prove the fault with OEM procedures, correct depowering, scan-tool SRS data, and approved back-probing methods. If testing confirms the module cannot drive or read the line with known-good wiring, then module-level repair or replacement may apply.

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: March 31, 2026