B1873

Code

Other B — Body

Turn Signal / Hazard Power Feed Circuit Short To Ground

Brand: Other

Type: B — Body

Views: UK: 16 EN: 33 RU: 23

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Damaged/abraded wiring harness contacting chassis ground
Corroded or pushed-pin connector creating a short
Faulty multifunction (turn signal/hazard) switch
Shorted lamp socket or lamp (including trailer connector)
Faulty Body Control Module (BCM) or internal output transistor
Aftermarket accessory (trailer harness, alarm) miswired or damaged

Symptoms

Turn signals and/or hazard lights inoperative on one or both sides
Fuses for turn/hazard circuit blow repeatedly
Rapid or abnormal flash rate (bulb-out sometimes reported)
Other functions on same module (BCM) showing faults or intermittent operation
Battery drain when hazard switch is on
Diagnostic trouble codes related to lighting or BCM present

What to check

Read and record stored DTCs and freeze-frame data from all modules
Inspect fuses and relays for the turn/hazard circuit and replace if blown
Visual inspection of wiring, connectors, lamp sockets, and trailer plug for damage or corrosion
Remove bulbs and check sockets for short to ground or corrosion
Verify wiring routing at steering column, door hinges, trunk, and underbody chassis penetration points
Check for aftermarket accessories (trailer harness, alarm) that may be tied into the circuit

Signal parameters

Expected feed voltage with ignition on and switch ON: approx. battery voltage (11–14.5 V) at the feed terminal
Expected feed voltage with switch OFF (no short): near 0 V at output but battery feed at fuse input ~11–14.5 V; if shorted, feed may be pulled toward ground under load (
Typical incandescent turn lamp current per bulb: 0.5–2.0 A (varies by bulb type); total circuit current depends on number of lamps
Continuity/Resistance: with circuit isolated and fuse removed, normal open/high insulation >10 kΩ; short to ground measured as
Voltage drop under load: should remain close to battery voltage; significant drop (>1 V) indicates a heavy short or high resistance connection

Diagnostic algorithm

Safety first: consult vehicle service manual, disable airbags if required for steering column work, and disconnect battery before making wiring repairs. Use appropriate PPE.
Retrieve all related codes and note when faults occur (key on, switch ON, hazards ON). Check BCM or instrument cluster for additional related DTCs.
Perform a visual inspection of harnesses, connectors, bulbs, sockets, and the trailer connector. Look for crushed, chafed, melted insulation, pinched wires where harness passes through grommets, and signs of corrosion or water ingress.
Check fuses/relays: locate the turn/hazard circuit fuse and relay. If fuse is blown, do not replace and immediately test for short. Remove the fuse and check for continuity between fuse feed (battery side) and ground; there should be no continuity. If continuity exists, a short is present downstream.
Isolation with meter: with ignition OFF and fuse removed, measure resistance between the feed side of the removed fuse and chassis ground. Low resistance indicates a short in the downstream wiring. If high/OL, short may be upstream or in module.
Isolate sections: disconnect connectors along the harness (multifunction switch, BCM connector, front/rear lamp connectors, trailer connector) one at a time while watching resistance between feed and ground. When resistance jumps to high/OL, the short is in the last reconnected section; use this to pinpoint the area.
Inspect and test the multifunction switch: remove and bench-test switch or measure output pins while operating switch. If switch output is shorted to ground with switch in ON position or shows unexpected continuity, replace the switch.
Inspect and test lamp sockets and bulbs: remove bulbs and check for continuity from socket positive to ground. Replace sockets or repair wiring as needed. Verify trailer connector and aftermarket splices.
Check BCM or output module: if wiring and switch are good and short remains tied to module output, suspect BCM internal driver short. Verify by isolating module connector and checking resistance; consult manufacturer procedures before replacing module.
Repair: repair or replace damaged wiring, connectors, sockets, switch, or BCM as identified. Use proper grommets, routing, and protection. Reassemble, reconnect battery, clear codes, and test turn signals and hazard function under normal and loaded conditions.

Likely causes

Wiring chafe at steering column, door hinge, or underdash contacting chassis
Internal short in turn signal/hazard switch
Water-intruded front/rear lamp connector or trailer socket creating ground path
Shorted bulb or lamp socket (insulation failure)
Damaged insulation where harness passes through firewall or trunk
Failed BCM output driver or internal short in module

Fault status

⚠️ Status

B1873 - Turn Signal / Hazard Power Feed Circuit Short To Ground: the power feed for the turn signal/hazard circuit has been detected shorted to chassis ground. This can cause inoperative signals, blown fuses, and related BCM faults.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.5 hours