B1501

Code

Other B — Body

Lamp Turn Signal Left Circuit Short To Battery

Brand: Other

Type: B — Body

Views: UK: 27 EN: 35 RU: 41

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Damaged wiring or chafed insulation causing contact with battery positive
Corroded or shorted bulb/socket causing constant feed
Aftermarket accessory or trailer wiring incorrectly tied into circuit
Faulty connector with pin contact bridged to 12V
Internal failure in the body control module (BCM) or lamp driver
Incorrect replacement bulb (wrong type/LED without resistor)

Symptoms

Left turn lamp (front or rear) stays on continuously or does not flash
Turn signal indicator may be illuminated steady on dash
Turn signal flash rate abnormal (fast/slow) or non-functioning
Other lighting circuits on same harness may behave erratically
Related error messages or lamps illuminated on instrument cluster

What to check

Read and record freeze frame/monitor data with scan tool; confirm B1501 active
Visual inspection of left turn lamp, socket, wiring harness and connector
Remove bulb and inspect for corrosion, broken filaments or conductive debris
Backprobe the lamp connector and measure voltage with lamp removed
Check for constant battery voltage on the circuit when lights/ignition are off
Disconnect harness at the lamp and measure voltage at disconnected connector

Signal parameters

Expected voltage with lamp OFF: ~0 V (no feed); Fault: ~12 V constant
Expected voltage when signaling: pulsed 9–14 V at ~1–2 Hz (turn rate)
Typical single filament incandescent turn bulb current: 0.5–2 A (varies by bulb)
Expected bulb resistance (cold): low ohms (varies by bulb type); infinite with bulb removed
Continuity: harness to lamp pin should show low resistance with connector engaged; open with disconnected circuit
If LED retrofit: expected current much lower; some LED modules require resistors or proper load detection

Diagnostic algorithm

Verify code: connect scan tool, confirm B1501 is current/historic and note any related codes.
Visual inspection: check left lamp assembly, socket, harness routing for damage, corrosion, or water.
Remove bulb: with bulb removed, backprobe the lamp connector. With ignition off and signals inactive, measure voltage to ground — if ~12 V present, a short to battery exists downstream of the module or at the harness.
Isolate at connector: disconnect the connector at the lamp and check for voltage on the harness side. If voltage disappears when connector disconnected, suspect lamp/socket or short at connector. If still present, short is upstream.
Trace harness: follow wiring toward vehicle, inspecting for chafe points, aftermarket splices or connectors. Perform wiggle tests while monitoring voltage.
Load test: temporarily connect a known-good bulb or test lamp to the harness and verify proper flashing operation and current draw. If the test lamp behaves normally, replace the original lamp/socket.
Check for aftermarket circuits: locate and remove/repair any trailer wiring or alarm/lighting taps tied into the left turn feed.
Check fuses/relays and BCM output: verify the control module output pin voltage and driver behavior using a scope or a safe current-limited bench test. If BCM output is stuck high, confirm software/calibration and consult manufacturer service info before module replacement.
Repair: repair damaged wiring, replace corroded connectors or lamp sockets, correct aftermarket splices; reseal housing to prevent moisture.
Verify: clear codes, retest function through multiple cycles, and road test. Re-scan to ensure code does not return.

Likely causes

Open/shorted harness near left rear/front lamp (rub through to positive)
Corroded socket pins making intermittent contact to battery
Aftermarket trailer/LED conversion tied to constant 12V instead of switched feed
Body module output or internal transistor stuck high
Bulb shorted internally (rare) or moisture bridging terminals

Fault status

⚠️ Status

Stored when the left turn signal lamp circuit is detected at constant battery voltage (short to battery), causing abnormal lamp behavior or module fault.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours