Code
B1507
FIAT
B — Body
Hazard flasher switch circuit
Views:
UK: 4
EN: 9
RU: 3
AI status
Completed
Completed
100%
Causes
- Faulty hazard flasher / hazard switch
- Damaged wiring or chafed insulation in switch circuit
- Poor or corroded connector pins at switch or BCM
- Blown fuse or failed flasher relay (if fitted)
- Faulty BCM or internal BCM input driver
- Water ingress or contamination at switch or connector
Symptoms
- Hazard lights do not activate or only work intermittently
- Hazard indicator on instrument cluster does not function or behaves erratically
- Turn signals affected or operate incorrectly when hazards selected
- One or more external hazard lamps not flashing
- Possible warning or fault message on dash
- Unexplained battery drain in some cases (if circuit shorted)
What to check
- Read stored codes and freeze-frame data with a diagnostic scanner; record related codes
- Visual inspection of hazard switch, connector, and wiring for damage, corrosion, or water ingress
- Check relevant fuses and relays for continuity and correct installation
- Operate hazard switch and observe lamp behavior and dash indicator
- Probe switch terminals with a multimeter/voltmeter while operating switch
- Back-probe BCM connector to confirm signal presence and continuity to switch
Signal parameters
- Supply voltage to switch: ~12 V (vehicle battery voltage) with ignition on or according to vehicle design
- Switch output to BCM: near 0 V when pulled to ground or ~12 V when driven high depending on circuit type; expected to change state when switch pressed
- Closed switch continuity: low ohms (
- Open switch resistance: very high/OL when not activated
- Ground continuity:
- No-load lamp circuit: open-circuit >1 MΩ when lamps removed (indicates no unintended short)
Diagnostic algorithm
- Connect a scan tool, read all fault codes and freeze frame; note any related BCM or lamp codes.
- Perform a visual inspection of the hazard switch, switch bezel, connectors and associated harness for damage, corrosion or moisture.
- Verify fuses and any flasher/relay are intact and seated. Replace if blown and retest.
- With ignition as required by vehicle, operate hazard switch while monitoring the switch supply and signal pin with a multimeter or oscilloscope. Confirm expected state change (approx. battery voltage on supply; signal toggles when pressed).
- Check continuity between the switch signal pin and the BCM input pin. Repair any open circuits or high-resistance connections.
- Check ground continuity for the switch/lighting circuit to chassis ground. Repair poor grounds.
- Inspect and test the external hazard lamps and their wiring; ensure lamp loads are correct and no bulbs are shorted or burnt out causing abnormal feedback.
- If wiring and switch test good, consider substituting a known-good hazard switch. If fault persists with a good switch, test BCM power and ground circuits and communication. Replace or repair BCM only after confirming wiring and switch integrity.
- After repairs, clear codes, cycle ignition and operate hazards to confirm the fault does not return. Road test if required to verify intermittent issues.
Likely causes
- Worn or failed hazard switch
- Loose/poor connector or corroded terminal at switch
- Open/short in harness between switch and BCM
- Blown fuse or intermittent relay
- BCM input fault (less common)
Fault status
Status
BCM reports a fault in the hazard flasher switch circuit (open/short/incorrect signal).
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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