B1891

Code

Other B — Body

Air Bag Tone Warning Indicator Circuit Short to Battery

Brand: Other

Type: B — Body

Views: UK: 23 EN: 35 RU: 25

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Wiring shorted to battery (+12V) in the air bag tone/warning indicator circuit
Corroded, damaged, or pinched harness or connector with positive feed contacting the indicator circuit
Faulty or shorted tone generator / chime module (speaker/buzzer)
Poor or missing ground that changes circuit behavior
Water intrusion or contamination in SRS connector/junctions
Improperly installed aftermarket accessories tapping 12V near the SRS indicator circuit

Symptoms

SRS / air bag warning lamp illuminated or flashing
Air bag tone/warning chime continuously sounding or not functioning as expected
Related SRS features may be disabled or flagged (diagnostic trouble codes stored)
Diminished or intermittent instrument cluster chime behavior
Possible inability to clear the SRS fault until repair is performed

What to check

Retrieve and record all SRS codes with an appropriate scan tool; note freeze frame data
Visual inspection of wiring harnesses, connectors and routing around the instrument cluster and under dash
Inspect for aftermarket installations near the cluster (alarms, stereos, power taps) that may tap 12V
Measure voltage at the tone indicator circuit with key ON and key OFF to see if battery voltage is present when it should not be
Check continuity/short to battery between the indicator circuit and vehicle positive terminal
Disconnect the tone generator (buzzer/speaker) and re-check for the fault to isolate component vs. wiring/module

Signal parameters

Normal: indicator circuit is driven by the SRS module or is open when not commanded; no constant battery feed present
Fault condition: circuit measures ~battery voltage (approx. 9–14 V) when it should be open or inactive
When tone generator is disconnected, circuit should not show a short to battery; if it does, wiring or module likely at fault
Resistance: tone generator/speaker will show low resistance when connected — compare to manufacturer spec; unexpected continuity to battery indicates a short

Diagnostic algorithm

Read and record all DTCs with an SRS-capable scan tool. Note any related codes and clear codes to see if B1891 returns.
Perform a careful visual inspection of the instrument panel, harnesses and connectors for damaged insulation, pinched wires, or signs of water intrusion. Pay attention to the area around the buzzer/chime and SRS module.
Disconnect battery negative terminal and wait per manufacturer safety procedure before touching SRS connectors. Reconnect battery only when safe to perform electrical tests.
With ignition ON (follow safety procedures), measure voltage at the tone indicator circuit terminal at the SRS module connector: verify whether battery voltage is present when the circuit should be inactive.
Disconnect the tone generator (buzzer/speaker). Clear codes and test; if the code does not return, suspect the tone generator assembly or its wiring. If code returns, suspect wiring or SRS module.
Perform continuity tests from the indicator circuit to battery positive to confirm short. Backprobe harness and follow wiring to locate shorted section.
Repair any damaged wiring or connectors (replace wiring sections, terminals, or harness clips). Protect and route harness away from sharp edges and heat sources.
If wiring and tone generator check good, suspect SRS module internal fault. Refer to manufacturer procedures — module replacement or repair often requires calibrated replacement and may require reprogramming or module coding.
After repairs, clear codes and perform SRS system readiness check with scan tool. Verify proper chime operation and that B1891 does not return.
Complete any required airbag system calibration, reconnection, and final road/ignition tests per manufacturer instructions.

Likely causes

Damaged insulation or chafed wiring contacting a 12V source near the dash
Accessory installed near instrument cluster connected to constant battery feed touching indicator wiring
Tone buzzer itself has failed internally and presents a short to battery
Connector pins pushed out or bent, causing cross-contact with a battery feed pin
SRS module output transistor failed and feeding battery voltage into the indicator circuit

Fault status

⚠️ Status

Air bag tone warning indicator circuit has a short to battery. SRS system has logged B1891; chime/indicator behavior abnormal and SRS readiness affected until fault is resolved.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours