OBD-II Code B1507: Turn Signal Circuit Failure

What Does B1507 Mean?

Code B1507 means the Body Control Module (BCM) or Combination Meter detected an electrical open in the turn signal circuit. The computer is not receiving the correct voltage return when you activate the turn signal stalk, usually due to a burned-out bulb, a failed switch, or a broken wire.

Technical definition: The official SAE definition for B1507 is 'Open in Turn Signal Circuit'. The control module logs this code when it detects a break in the front or rear turn signal circuit while battery voltage is 9.5V or higher.

Can I Drive With B1507?

Yes, But With Caution. Yes, but fix it immediately. Driving without turn signals is illegal and dramatically increases accident risk. Police actively issue tickets for inoperable signals, with fines ranging from $25 to $250 depending on your state.

Common Causes

• Burned Out Turn Signal Bulb (Very Common) — A burned-out filament severs the electrical path, creating an open circuit that the car's computer immediately detects as a fault.
• Defective Multifunction Switch (Very Common) — The turn signal stalk on your steering column wears out internally from repeated use, breaking the electrical contact required to send the signal to the BCM.
• Aftermarket LED Bulb Installation (Common) — Modern vehicles expect the specific electrical resistance of incandescent bulbs. Low-resistance LED bulbs trick the computer into thinking the circuit is open, triggering B1507 and hyper-flashing.
• Damaged Wiring or Corroded Connectors (Common) — Wires inside the steering column chafe and break, or moisture causes corrosion inside the bulb sockets, blocking the electrical signal.
• Blown Fuse or Failed Flasher Relay (Less Common) — A blown fuse cuts all power to the circuit. On older vehicles, a mechanical flasher relay can fail internally; on newer cars, this relay is integrated into the BCM.
• Faulty Body Control Module (BCM) (Rare) — The computer module controlling the turn signals has failed internally. This is the most expensive cause and requires ruling out all wiring and switch issues first.

Symptoms

• Turn signals hyper-flash (blink rapidly) — The turn signal blinks at twice the normal speed (over 120 flashes per minute), indicating a burned-out bulb or an LED resistance mismatch.
• Turn signals fail to activate — Neither the left nor right turn signal illuminates when you move the stalk.
• Wipers or high beams fail simultaneously — Because the multifunction switch controls multiple systems, a failure inside the stalk often kills the wipers, high beams, and turn signals at the same time.
• Hazard lights fail — Hazard lights use the same bulbs and wiring paths; an open circuit often disables them as well.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this code.

Common Fixes & Costs

• Replace Turn Signal Bulb — Parts: $5-$20, Labor: $0-$25, ~0.2 hr book time (DIY)
• Install LED Load Resistors — Parts: $15-$30, Labor: $0-$50, ~0.5 hr book time (DIY)
• Replace Multifunction Switch — Parts: $50-$250, Labor: $100-$200, ~1.0 hr book time (Intermediate)
  Ford F-150 (2004-2008): OEM 6L3Z-13K359-AA (Alt: Standard Motor Products CBS-1332)
  Toyota Tacoma (2016-2023): OEM 84140-04090 (Alt: Standard Motor Products CBS-2239)
  Chevrolet Silverado (2003-2007): OEM 20940099 (Alt: Dorman 2330897)
• Replace Blown Fuse or Relay — Parts: $5-$30, Labor: $0, ~0.1 hr book time (DIY)
• Repair Damaged Wiring or Socket — Parts: $10-$50, Labor: $120-$350, ~2.0 hr book time (Professional)

Used vs. New Parts: Buying Guide

When a used part is worth it: Only on older vehicles (15+ years) where a new OEM part is discontinued or prohibitively expensive.

Donor-vehicle mileage cap: roughly under 80000 miles for the part to have meaningful remaining life.

Donor quality checklist:

• Verify the exact part number match, as switches vary wildly based on trim options (e.g., fog lights, auto-wipers).
• Ensure the stalk clicks firmly into place and the printed icons are not heavily worn.

Decision logic:

• If A new aftermarket switch (Dorman, Standard) is less than 50% more expensive than a used one → Buy the new aftermarket part for the warranty and zero internal wear.
• If Replacing the switch requires removing the steering wheel and airbag → Buy a new OEM part. Do not risk having to repeat a dangerous, labor-intensive job because a used part failed early.

Warranty tradeoff: Used switches offer 30 days. New aftermarket offers 1 year to lifetime. Always choose new for electrical switches if the budget allows.

Worst-case if a used part fails: $200-$400 in repeated labor costs if a used switch fails shortly after installation.

What Happens If You Wait — Timeline

1. Immediate: Turn signal stops working or hyper-flashes. Accident risk increases significantly. (MPG impact: 0%% · Added cost: $0)
2. 0-3 months: You receive a traffic ticket for defective safety equipment. (MPG impact: 0%% · Added cost: $85-$250)
3. 3-12 months: Vehicle fails annual state safety inspection, preventing registration renewal. (MPG impact: 0%% · Added cost: $100+ in fees)

Cost of Not Fixing It

• Immediate: High risk of a side-swipe or rear-end collision because other drivers cannot anticipate your lane changes. (Added cost: Varies (Insurance deductibles and liability costs))
• 0-3 months: Receiving a traffic citation for defective safety equipment. (Added cost: $85-$250)
• 3-12 months: Failing your mandatory annual state safety inspection, preventing vehicle registration renewal. (Added cost: $100+ (Inspection and re-inspection fees))

Diagnosis Steps

1. Check Bulbs and Fuses
   Visually inspect all four turn signal bulbs for broken filaments. Locate the interior fuse box and verify the turn signal/hazard fuse is intact.
   Tools: Flashlight, fuse puller (Beginner)
2. Test All Stalk Functions
   Activate the wipers, high beams, and hazard lights. If the hazard lights work but the turn signals do not, the bulbs and wiring are fine, and the multifunction switch is the culprit.
   Tools: None (Beginner)
3. Scan for Codes and Live Data
   Connect a scan tool and view live data for the Body Control Module (BCM). Monitor the 'Turn Signal Switch' PID. If the status does not change to 'Left' or 'Right' when you move the stalk, the switch or its direct wiring has failed.
   Tools: OBD-II Scan Tool (with BCM live data capability) (Intermediate)
4. Test Voltage at the Bulb Socket
   Remove the non-working bulb. Set a multimeter to DC Volts. Activate the turn signal and probe the socket contacts. You should see a pulsing 10V-14V. If you see voltage, the socket or bulb is bad. If you see zero voltage, the problem is upstream.
   Tools: Multimeter (Intermediate)
5. Perform a Circuit Integrity Check
   Disconnect the harness at the multifunction switch and the BCM. Use a multimeter set to Ohms to test the signal wire for continuity (should be <1 ohm) and check for a short to ground (should be >10k ohms).
   Tools: Multimeter, vehicle-specific wiring diagram (Advanced)

When This Code Triggers (Freeze-Frame Conditions)

• Battery Voltage: 9.5V - 16V (The BCM requires a minimum of 9.5V to run the diagnostic monitor. Low battery voltage prevents the test or sets false codes.)
• Turn Signal Switch Status: Left or Right (The code sets when the driver commands the turn signal, but the module detects zero electrical load on the circuit.)

Related Codes

• B1508 — B1508 indicates a short circuit and will instantly blow the turn signal fuse. B1507 is an open circuit and rarely blows fuses.
• B1342 — Indicates an internal ECU fault. If B1342 is present alongside B1507, the Body Control Module (BCM) has likely failed and requires replacement.
• U0140 — Means 'Lost Communication With Body Control Module'. The entire BCM is offline. Diagnose U0140 first, as B1507 is just a symptom of the dead module.

Climate & Environmental Factors

• High Humidity and Road Salt: Moisture and salt accelerate corrosion inside bulb sockets and harness connectors, creating high electrical resistance that triggers the open circuit code.
• Extreme Cold: Freezing temperatures make the plastic components inside the multifunction switch brittle, causing them to snap under normal use.
• Vibration: Constant road vibration chafes wiring insulation against the metal steering column, eventually severing the wire.

How to Talk to a Mechanic About This Code

Say this: "I have code B1507 and my left turn signal is hyper-flashing. I've verified the bulbs and fuses are good. I need a diagnostic on the multifunction switch and its circuit."

Shows you've done basic troubleshooting, directing the mechanic away from charging you $150 to change a $5 bulb, and focuses them on the switch and wiring.

Avoid saying:

• 'My blinker is broken, fix it.'
• 'Just do whatever you think is best.'

Questions to ask before authorizing the repair:

• Did you test the output from the multifunction switch directly?
• If you are recommending a BCM replacement, what specific tests led you to condemn the module over the wiring?

Where to Take It: Dealer vs Independent vs Chain

• Dealer: Use only if the BCM requires replacement and programming.
  Best for: Vehicles under warranty., Complex repairs requiring BCM programming.
  Downsides: Significantly higher labor rates., Will default to replacing entire expensive assemblies rather than repairing a single wire. (Typical cost: +50% vs. baseline)
• Independent Shop: Best fit for most B1507 situations. This is standard electrical work.
  Best for: Out-of-warranty vehicles needing a multifunction switch or wiring repair.
  Downsides: May lack the specific software to program a new BCM if required. (Typical cost: +0% vs. baseline)
• Chain Shop: Avoid for diagnosing the root cause if a new bulb doesn't fix it.
  Best for: Simple bulb or fuse replacements.
  Downsides: Not equipped for in-depth electrical circuit tracing. (Typical cost: -10% vs. baseline)

When to Walk Away From the Repair

If the estimated repair cost exceeds 40% of the car's private-party value, evaluate if the investment is worth it.

• Car worth $5000, fix is $300: Fix it. This is a standard cost for a multifunction switch replacement.
• Car worth $2500, fix is $1200: Walk away. The repair (likely a BCM replacement) is nearly 50% of the car's value.

What Scan Tool You Need for This Code

Minimum: A scanner that reads Body Control Module (BCM) live data to view the turn signal switch status.

A $20 code reader only shows the B1507 code. It cannot tell you if the BCM is receiving the 'left' or 'right' command from the stalk, which is mandatory for diagnosing the switch.

Budget: Autel AP200 (~$60) — Connects to your smartphone and reads live data from the BCM, allowing you to verify if the switch is sending signals to the computer.

Mid-range: Foxwell NT510 Elite (~$150) — Adds bidirectional control. You can command the turn signals ON directly from the scanner. If they flash via the scanner but not the stalk, the switch is definitively broken.

Professional: Autel MaxiCOM MK808 (~$500) — Provides full OE-level diagnostics, bidirectional control, and module programming capabilities.

Rent vs buy: Buy the Autel AP200. Parts store rental scanners rarely access BCM live data, making them useless for diagnosing this specific code.

How to Clear the Code After You Fix It

1. Fix the underlying fault (replace bulb, switch, or repair wire).
2. Connect an OBD-II scan tool to the vehicle.
3. Navigate to the Body Control Module (BCM) menu and clear the DTCs.
4. Turn the ignition off, then on, and operate the turn signals for 30 seconds to confirm the repair.

Drive cycle: No driving is required. Simply operate the left and right turn signals, and the hazard lights, for 30 seconds each while parked.

Watch out for:

• Clearing the code without fixing the burned-out bulb or switch will cause the code to return the exact second you use the turn signal again.

Will This Fail Emissions / State Inspection?

No — by itself this code doesn't fail OBD inspection (but it can keep readiness monitors from setting, which causes a separate fail).

• New York: Inoperative turn signals result in an automatic failure of the mandatory annual safety inspection.
• Texas: Vehicles requiring safety inspections will fail immediately if directional signals do not illuminate and flash properly.
• California: Does not affect smog checks, but will cause a failure during brake/light inspections required for salvaged titles.

Most Commonly Affected Vehicles

• Ford F-150 (2004-2008) — Notorious for multifunction switch failures. Aftermarket replacements from Dorman or Standard Motor Products are highly recommended and easy to install.
• Ford Explorer (2002-2010) — The turn signal stalk frequently loses contact internally, disabling signals and wipers simultaneously.
• Toyota Tacoma (2016-2023) — B1507 is almost always triggered by owners installing aftermarket LED turn signal bulbs without adding the necessary 50W 6-ohm load resistors.
• Chevrolet Silverado / Sierra (1999-2007) — The multifunction switch is a high-failure item. The flasher 'click' is generated by the instrument cluster speaker; a silent signal often points to a cluster issue.
• Subaru WRX / Forester (2015-2024) — The Combination Meter Assembly directly controls the turn signals. B1507 requires checking the harness between the meter and the light assemblies.

Manufacturer-Specific Notes

• Ford: On 2000s-era Fords, B1507 almost exclusively points to a failed multifunction switch. Diagnosis is straightforward and parts are cheap.
• Toyota / Lexus: Highly sensitive to LED bulb upgrades. The BCM interprets the low resistance of an LED as a burned-out bulb, instantly triggering B1507 and hyper-flashing.
• General Motors (GM): The flasher 'click' sound is electronically generated by a speaker in the instrument cluster. If the signals work but are silent, the cluster speaker has failed, not the relay.
• Subaru: The Combination Meter (gauge cluster) acts as the central control unit for turn signals. A fault here requires tracing circuits directly from the dashboard to the lights.

Real Owner Stories

2019 Toyota C-HR with aftermarket LEDs

Installed LED turn signal bulbs and immediately triggered a B1507 code with hyper-flashing.

What they tried:

1. Cleared the codes, but B1507 returned instantly upon signaling.

Outcome: The BCM interpreted the low resistance of the LEDs as an open circuit. The owner fixed it by wiring 50W 6-ohm load resistors in parallel with the new bulbs.

Lesson: When upgrading to LEDs, B1507 and hyper-flashing indicate a resistance mismatch, not a broken circuit. Buy CANbus-ready bulbs or install resistors.

2016 Toyota Prius at 50k miles

Found a B1507 code in the 'history' folder during a routine scan. All lights worked perfectly.

What they tried:

1. Verified battery voltage (12.4V) and tested all stalk functions.

Outcome: Cleared the code and it never returned. It was caused by a transient voltage drop during a cold start weeks prior.

Lesson: A 'history' code with no active symptoms does not require repair. Clear it and monitor.

2019 Toyota Tacoma with bizarre symptoms

The right turn signal only worked when the brake pedal was pressed.

What they tried:

1. Replaced taillight bulbs and checked trailer wiring.

Outcome: The dealer diagnosed an internal short in the Combination Meter (gauge cluster) and replaced it for $900.

Lesson: On modern vehicles, the gauge cluster often controls turn signal logic. Bizarre, conditional electrical failures usually point to a faulty control module.

How to Prevent This Code From Triggering

• Apply dielectric grease to bulb sockets (Whenever replacing a bulb) — Seals out moisture and road salt, preventing the corrosion that causes high resistance and open circuits.
• Avoid hanging heavy items on the turn signal stalk (Daily habit) — Heavy lanyards put constant physical stress on the internal plastic components of the multifunction switch, snapping them prematurely.
• Inspect headlight and taillight housings for condensation (Every 6 months) — Catching water intrusion early prevents it from pooling in the bulb sockets and destroying the wiring harness.

Frequently Asked Questions

Can I just replace the bulb to fix a B1507 code?

Yes. Always check the bulbs first, as a burned-out filament creates the exact open circuit that triggers B1507. It is the cheapest and most common fix.

My turn signals work, but I have a B1507 code. Why?

This happens if the fault is intermittent or stored in 'history' from a past voltage drop. Clear the code with a scanner and see if it returns. If it doesn't, no repair is needed.

I installed LED bulbs and now have B1507. Why?

LEDs have much lower electrical resistance than standard halogen bulbs. The computer interprets this low resistance as a burned-out bulb. Install 50W 6-ohm load resistors or use CANbus-ready LEDs to fix it.

Is it expensive to fix code B1507?

It ranges from $5 for a new bulb to $300 for a multifunction switch replacement at a shop. Most repairs are simple and fall well under $200.

My wipers and high beams also stopped working. Is that related?

Yes. The wipers, high beams, and turn signals all share the multifunction switch assembly on the steering column. When the switch fails internally, multiple functions die simultaneously.

Key Takeaways

• Code B1507 indicates an electrical open in the turn signal circuit, most commonly caused by a $5 burned-out bulb or a failed multifunction switch.
• Installing aftermarket LED bulbs without 50W 6-ohm load resistors triggers this code and causes hyper-flashing on most modern vehicles.
• Test the multifunction switch by checking if your wipers and high beams still work; simultaneous failure guarantees the $150-$300 switch assembly is the culprit.
• Never replace the Body Control Module (BCM) for this code without first using a multimeter to verify 12V power reaches the bulb socket.