B0259

Code

Generic B — Body

Airbag sensor circuit malfunction

Brand: Generic

Type: B — Body

Views: UK: 15 EN: 22 RU: 13

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Faulty airbag/impact sensor (internal fault)
Damaged or corroded wiring harness or connector at the sensor
Poor or intermittent electrical connection (loose pin, bent terminal, corrosion)
Short to ground or battery voltage on the sensor signal or power lead
Faulty SRS control module or poor ground at the module
Previous repair or aftermarket accessory damage to wiring

Symptoms

SRS / airbag warning lamp illuminated on dash
Possible disablement of airbag deployment (SRS fault state)
Other related SRS faults or communication errors may be present
Stored freeze-frame data and fault history in SRS control module
Occasional code return only when vehicle moves or on hard hits if circuit intermittent

What to check

Retrieve all stored SRS codes and freeze-frame data with a capable scan tool
Confirm battery voltage is stable (12.4–14.5 V) and connections are clean
Visual inspection of wiring and connectors at the affected sensor(s) and SRS module
Wiggle test wiring while monitoring live data/scan tool for intermittent faults
Check for corrosion, bent pins, or contaminated connector terminals
Measure continuity and resistance of the sensor circuits with ignition off

Signal parameters

Typical reference/supply voltage: approximately 5 V or regulated module supply (varies by manufacturer)
Expected sensor output signal: within 0.2–4.8 V (manufacturer-specific — check service data)
Open circuit: infinite resistance / no continuity between sensor signal and module
Short to ground: near 0 Ω between signal and chassis ground
Short to battery: near 0 Ω between signal and battery positive (or signal stuck at battery voltage)

Diagnostic algorithm

Read all SRS codes and freeze-frame with a qualified scan tool; record related codes and history.
Verify battery voltage and charging system; charge or stabilize battery if low and clear codes then recheck.
Perform detailed visual inspection of the sensor, harness, and connectors for damage, corrosion, or aftermarket modifications.
With ignition off, disconnect the sensor connector and inspect pins; clean or repair damaged terminals as needed.
Check continuity and resistance between sensor connector and SRS module pins; look for opens, high resistance, or short circuits.
Reconnect and backprobe the connector with key ON (engine OFF). Measure reference power, ground, and signal while working the harness to detect intermittents.
If available, use an oscilloscope to view sensor waveform during vehicle movement or simulated inputs (follow vehicle-specific procedures).
Repair identified wiring faults (repair, solder, crimp, and protect with heat-shrink or replace harness sections). Replace corroded connectors.
If wiring checks good and sensor still out of expected range, replace the suspect airbag/impact sensor with a matching OEM part.
After repairs, clear codes and perform SRS system self-tests with scan tool; verify lamp extinguishes and no new B0259 returns. Re-scan after a test drive.
If fault persists after sensor and wiring replacement, evaluate SRS control module and module grounds; consult manufacturer service information for module bench tests or reprogramming.

Likely causes

Corroded or loose connector at the sensor
Broken or chafed wiring harness to the sensor (intermittent open/short)
Failed impact/airbag sensor
Poor ground or power supply to SRS module
Connector pushed out or mis-routed during service

Fault status

⚠️ Status

SRS warning lamp illuminated; airbag system fault stored (airbag sensor circuit malfunction). System may inhibit deployment until the circuit fault is cleared and verified.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours