B1801 on Lexus
Lamp Turn Signal Front Output Circuit Short to Ground
B1801 on Lexus vehicles indicates lamp turn signal front output circuit short to ground. Au7o has documented this code across 1 Lexus model — most commonly on NX. B1801 is a manufacturer-specific body code (most commonly seen on Ford and related makes) indicating the lighting control module detected a short to ground on the front turn-signal lamp output circuit. The module monitors the current it sends to the bulb and flags a fault when that circuit is pulled to ground instead of behaving normally. On other manufacturers this exact code string can mean something different, so the definition should be confirmed against the specific make. The practical effect is usually an inoperative or improperly behaving front turn signal.
Common Causes of B1801
- •Short to ground in the front turn-signal wiring
- •Chafed or pinched harness near the front lamp
- •Corroded or damaged bulb socket/connector
- •Faulty turn-signal bulb
- •Water intrusion in the front lamp assembly
- •Internal fault in the lighting/body control module
B1801 on Lexus by Model
Lexus NX(1 issue)
- Steering Column Spiral Cable Weld Failure Deactivates Driver Airbag (Recall 25V040000)2023-2024
An electrical connection inside the steering column's spiral cable assembly — the coiled ribbon that carries signals to the rotating steering wheel — may be insufficiently welded. The connection can separate in service, which deactivates the driver's frontal airbag and puts the vehicle out of compliance with FMVSS 208, Occupant Crash Protection. Critically, campaign 25V040000 targets vehicles that may have been incorrectly repaired under the earlier recall 23V-480, so a car whose records show that prior repair is not necessarily safe. Owner letters were mailed March 17, 2025; the Lexus campaign number is 25LA02.
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View B1801 across all makes →Frequently Asked Questions
What does B1801 mean on Lexus?▼
B1801 stands for "Lamp Turn Signal Front Output Circuit Short to Ground." B1801 is a manufacturer-specific body code (most commonly seen on Ford and related makes) indicating the lighting control module detected a short to ground on the front turn-signal lamp output circuit. The module monitors the current it sends to the bulb and flags a fault when that circuit is pulled to ground instead of behaving normally. On other manufacturers this exact code string can mean something different, so the definition should be confirmed against the specific make. The practical effect is usually an inoperative or improperly behaving front turn signal. On Lexus specifically, this code is documented across 1 model.
What causes B1801 on Lexus vehicles?▼
Common causes on Lexus: Short to ground in the front turn-signal wiring, Chafed or pinched harness near the front lamp, Corroded or damaged bulb socket/connector, Faulty turn-signal bulb, Water intrusion in the front lamp assembly. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix B1801 on a Lexus?▼
Repair costs vary widely depending on the root cause and specific Lexus model.
Which Lexus models have B1801 documented?▼
Au7o has documented B1801 on 1 Lexus model: NX.