B1756

Code

Other B — Body

Hazard Flash Output Circuit Short To Ground

Brand: Other

Type: B — Body

Views: UK: 20 EN: 26 RU: 19

AI status

Completed

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Page language: EN

Causes

Damaged or chafed wiring harness where the hazard output conductor contacts chassis ground
Shorted or corroded connector (pin-to-pin or pin-to-ground) at lamp, switch, or BCM
Failed hazard switch, multifunction switch, or turn/hazard relay with internal short
Faulty or internally shorted BCM / body control module
Burnt out or shorted lamp (internal short or aftermarket LED conversion with incorrect resistor)
Aftermarket accessory or trailer wiring incorrectly tied into the hazard circuit

Symptoms

Hazard lights do not operate or operate intermittently
One side or multiple lamps fail to flash when hazards are on
Hazards may not activate and DTC B1756 is stored
Blown fuse for turn/hazard circuit or unexpected fuse failures
Other lighting functions controlled by same module may be affected

What to check

Retrieve and record all stored codes and freeze frame data; note any related lamp or network codes
Visual inspection of wiring harnesses, connectors, and lamps for damage, corrosion, or pinched wires
Inspect fuses and relays for the hazard/turn circuits
Check that bulbs are correct type and seated; remove bulbs to see if code clears or behavior changes
Disconnect aftermarket accessories and trailer connectors that tie into the turn/hazard circuit
Backprobe BCM/hazard output pin and measure voltage when hazards commanded

Signal parameters

Output state off: near 0 V at output when module not commanding (some modules may sit at ground or low impedance)
Output state on: pulsed battery voltage (~11–14 V) when hazards/turns are commanded; pulse frequency typically ~1–2 Hz
Expected duty cycle: roughly 30–70% depending on vehicle (rapid flash if low load or bulb out)
Normal load current per side: typically < 5 A per lamp circuit for incandescent; higher surge possible on activation
Short condition: near 0 Ω to ground or excessive current draw (> normal lamp current), voltage droops when commanded

Diagnostic algorithm

Record codes, battery voltage, and any related network/lighting DTCs. Disconnect battery if required by vehicle procedures before doing connector work.
Perform visual inspection of hazard/turn wiring from BCM to all lamps, switch and any splice points. Look for chafe at door hinges, under dash and near mounting points.
Inspect bulbs at all corners. Remove bulbs and cycle hazards: if code clears or current draw drops, suspect a lamp or socket (or LED retrofit issue).
With hazards commanded ON, backprobe the BCM hazard output pin and measure voltage. If voltage remains near 0 V and output should be pulsed, suspect short or driver failure.
With the load (bulbs) disconnected at the lamp connectors, measure resistance from the BCM output pin to chassis ground. Low resistance (< 5–10 Ω) indicates a short to ground in the harness between BCM and disconnect point.
Isolate the short by disconnecting connectors in sections (BCM harness, in-line junctions, switch, lamp connectors) and checking continuity to ground at each segment until the faulted section is found.
If short exists only when a particular connector is connected, inspect and repair that connector/wire (repair pigtail, replace socket, re-pin connector).
If harness and components test good, substitute or bench-test the hazard switch/relay where applicable. If still unresolved, consider BCM output driver failure—verify with service manual before replacing module.
After repair, clear codes and verify proper operation of hazards and related lighting on road/test bench; recheck for DTC reappearance.

Likely causes

Wiring chafe or pinched harness in steering column, door hinge, or behind dash
Corroded connector at turn/hazard switch or at front/rear lamp connector
Shorted replacement lamp or LED retrofit without proper load resistor
Faulty hazard switch or relay
BCM output driver failure (less common after wiring and connectors checked)

Fault status

⚠️ Status

Controller detected a short to ground on the hazard flasher output circuit. Hazard output may be disabled until fault is cleared. Check wiring, connectors, lamps, and module output driver.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours