OBD-II Code P1703: Brake Switch Signal Malfunction

What Does P1703 Mean?

The P1703 code means the Powertrain Control Module (PCM) received an unexpected signal from the brake pedal switch during a self-test. The computer cannot determine if you are pressing the brake pedal. The PCM expects the switch signal to change voltage when the pedal is pressed; if the signal remains static, it triggers the code.

Technical definition: SAE/OBD-II defines P1703 as "Brake On/Off Switch Out of Self-Test Range." During a self-test, the PCM detected the brake pedal position (BPP) switch signal did not cycle correctly or remained in an unexpected state. This indicates an open or short in the brake switch circuit or stop lamp circuits.

Can I Drive With P1703?

Yes, But With Caution. You can drive, but it poses a severe safety risk. If the brake switch fails, your brake lights will not illuminate, drastically increasing the risk of a rear-end collision. Conversely, if they are stuck on, they confuse other drivers and drain the battery. Driving without functional brake lights is illegal; inspect the vehicle immediately.

Common Causes

• Broken brake pedal stop pad (Very Common) — On Ford and Hyundai/Kia vehicles, a small plastic pad on the brake pedal arm presses the switch plunger. These pads become brittle and crumble, creating a gap that leaves brake lights stuck on 🎬 See how to easily fix brake lights that stay on. and triggers the code.
• Faulty or misadjusted brake light switch (Very Common) — The switch breaks internally, gets knocked out of alignment, or sticks. Modern switches have separate circuits for the lights and the PCM; one circuit fails while the other works, triggering a code even if brake lights function.
• Blown fuse (Common) — A blown fuse cuts power to the brake switch circuit. Without power, the switch cannot send a signal to the PCM.
• Damaged wiring or corroded connectors (Common) — Wires near the pedal fray or short from physical contact. Connectors corrode from moisture, causing intermittent or complete signal loss.
• Aftermarket LED brake lights (Less Common) — LED bulbs have different electrical resistance than incandescent bulbs. This alters the circuit voltage, confusing the computer during self-tests.
• Incorrect diagnostic testing (Less Common) — Running a Key On Engine Running (KOER) self-test without pressing the brake pedal when prompted forces the PCM to log a false P1703.
• Faulty Powertrain Control Module (PCM) (Rare) — The computer module receiving the signal has an internal fault. Consider this only after exhaustively ruling out the switch, pad, and wiring.

Symptoms

• Brake lights don't work or are stuck on — Your brake lights fail to illuminate when you press the pedal, or they stay on constantly when your foot is off the brake.
• Cannot shift out of Park — The shift interlock requires a signal from the brake switch before shifting out of Park. A bad signal prevents the interlock from releasing.
• Engine fails to start (Push-Button Start) — Vehicles with a push-button ignition require a valid brake pedal signal to crank the engine.
• Cruise control won't engage — The cruise control system relies on the brake switch signal to disengage. A faulty signal disables the system as a safety measure.
• ABS or Traction Control lights are on — Anti-lock brake and traction control systems use the brake signal for calculations. A faulty signal triggers their warning lights.
• Check Engine Light is on — The Malfunction Indicator Lamp (MIL) on your dashboard illuminates.

Diagnostic Flowchart

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

Common Fixes & Costs

• Replace brake pedal stop pad — Parts: $5-$15, Labor: $30-$75, ~0.5 hr book time (DIY)
• Replace the brake light switch — Parts: $15-$75, Labor: $60-$120, ~0.8 hr book time (DIY)
• Replace a blown fuse — Parts: $1-$5, Labor: $0, ~0.1 hr book time (DIY)
• Adjust or realign the brake light switch — Parts: $0, Labor: $30-$60, ~0.4 hr book time (DIY)
• Repair faulty wiring or connector — Parts: $10-$30, Labor: $150-$300, ~2 hr book time (Professional)

DIY vs Professional

• Replace a blown fuse — Beginner:
  Tools: Fuse puller, owner's manual.
• Replace brake pedal stop pad — Beginner:
  Tools: Flashlight, small pick or flathead screwdriver.
• Replace the brake light switch — Beginner:
  Tools: Basic hand tools, flashlight.
• Repair faulty wiring or connector — Beginner:
  Tools: Multimeter, wiring diagrams, wire strippers, crimpers, heat shrink tubing.
• Replace PCM or BCM — Beginner:
  Tools: Professional diagnostic scan tool for programming.

Used vs. New Parts: Buying Guide

When a used part is worth it: Never buy used for a switch or stop pad. These parts are inexpensive new, and a used part has a high likelihood of early failure.

Donor-vehicle mileage cap: roughly under 20000 miles for the part to have meaningful remaining life.

Donor quality checklist:

• Verify the exact part number.
• Avoid parts from rust-belt regions.
• Check that the plastic plunger is not brittle.

Decision logic:

• If The new part costs less than $75. → Always buy new.
• If The vehicle is older and a new OEM part is discontinued. → A quality aftermarket new part is the first choice.
• If The failure is the plastic stop pad. → Never buy used. The plastic becomes brittle with age.

Warranty tradeoff: Used parts have a 30-90 day warranty. New aftermarket parts offer 1-year to lifetime warranties.

Worst-case if a used part fails: $100-$200

What Happens If You Wait — Timeline

1. Immediate: Check Engine Light illuminates. Brake lights stick on or fail completely. Cruise control disables, and shifting from Park is blocked. (MPG impact: 0%% · Added cost: $0)
2. 0-1 week: Stuck brake lights drain the battery overnight, requiring a jump-start or causing premature battery failure. (MPG impact: 0%% · Added cost: $150-$250)
3. 1-3 months: Driving without brake lights causes a rear-end collision. ABS and Traction Control systems log secondary faults. (MPG impact: 0-2%% · Added cost: $500+)
4. 3+ months: Wiring shorts overload circuits, destroying the Body Control Module (BCM) or Powertrain Control Module (PCM). (MPG impact: 0-5%% · Added cost: $500-$1500)

Cost of Not Fixing It

• Immediate: Major safety hazard. Risk of a rear-end collision is extremely high. (Added cost: $500+)
• 0-1 month: A switch stuck 'on' drains the battery overnight, requiring a jump-start or a new battery. (Added cost: $150-$250)
• 1-6 months: Continued stress on ABS/Traction Control modules logs secondary faults. Wiring shorts destroy the BCM. (Added cost: $500-$1500)

Diagnosis Steps

1. Check Brake Light Function
   Have an assistant stand behind the car while you press the brake pedal. Stuck, dead, or flickering lights confirm a brake switch circuit fault.
   Tools: An assistant (Beginner)
2. Inspect the Brake Pedal and Fuses
   Look under the dashboard at the brake pedal arm. Check the floor mat for crumbled plastic pieces from a broken stop pad. Verify all brake and stop lamp fuses using the owner's manual.
   Tools: Flashlight, owner's manual (Beginner)
3. Check for Technical Service Bulletins (TSBs)
   Search for manufacturer TSBs related to P1703. Manufacturers frequently release software updates or specific repair procedures for known issues causing this code.
   Tools: Internet access (Intermediate)
4. Scan Live Data
   Use an OBD-II scanner to monitor the 'Brake On/Off' (BOO) PID. It must read 'Off' with the pedal released and 'On' when pressed. An incorrect reading confirms a signal failure.
   Tools: OBD-II scanner with live data (Beginner)
5. Test the Brake Light Switch
   Remove the switch and use a multimeter set to continuity. Actuate the plunger by hand and confirm each circuit opens and closes correctly (near-zero resistance when closed, infinite when open).
   Tools: Multimeter, wiring diagram (Intermediate)
6. Test the Switch Connector
   Disconnect the switch. Use a multimeter to verify constant 12V+ power on the supply pin and a solid ground on the chassis pin. Missing power indicates a blown fuse or broken wire.
   Tools: Multimeter, wiring diagram (Intermediate)
7. Inspect the Wiring Harness
   Trace the wiring harness from the switch to the control module. Look for chafing or breaks. Perform a 'wiggle test' while monitoring live data to expose intermittent shorts.
   Tools: Flashlight (Intermediate)
8. Test BPP Sensor Voltage (Advanced)
   For vehicles with a Brake Pedal Position sensor, back-probe the signal wire. Voltage must sit around 1.0V at rest and rise smoothly to over 3.5V when fully depressed. Jumps or dropouts indicate a failed sensor.
   Tools: Multimeter, back-probe pins (Advanced)
9. Test Hyundai/Kia TPS Voltage (Advanced)
   If P1703 refers to the Throttle Position Sensor (Hyundai/Kia), back-probe the TPS signal wire. Voltage must be 0.4V-0.6V at idle and rise smoothly to 4.5V at wide-open throttle.
   Tools: Multimeter, back-probe pins (Advanced)
10. Perform a Scope Test (Professional)
    Back-probe the signal wire at the PCM with an oscilloscope. Press the brake pedal to verify a clean square wave transitioning instantly from 0V to 12V. Noisy patterns indicate failing contacts.
    Tools: Oscilloscope, back-probe pins (Professional)

When This Code Triggers (Freeze-Frame Conditions)

• Vehicle Speed: 0 mph (The code is set during the Key On, Engine Off (KOEO) self-test before driving.)
• RPM: 0 or Idle (~750 RPM) (Logged at startup during initial checks.)
• Brake Pedal Status (PID): On or Off (Stuck) (The value shown is the opposite of the pedal's actual physical state.)
• Engine Coolant Temp: Ambient Temperature (The self-test runs at cold start.)

Related Codes

• P1572 — Brake Pedal Switch Circuit Malfunction. Seeing this alongside P1703 strongly confirms the fault is in the brake switch circuit.
• C1440 — Pressure Transducer Main Signal Faulted. The ABS module sees a mismatch between the brake light switch status and brake fluid pressure.
• U0140 — Lost Communication With BCM. A network fault prevents the brake signal from reaching the PCM, indirectly causing P1703.
• P0122 — TPS Circuit Low Input. On Hyundai/Kia models, having both P1703 and P0122 confirms a Throttle Position Sensor failure.

Climate & Environmental Factors

• High Humidity / Moisture: Accelerates corrosion on electrical connectors and wiring. Moisture creates unintended electrical paths, leading to short circuits.
• Extreme Temperatures: Temperature cycles cause plastic components, like the brake pedal stop pad, to become brittle and crumble. Extreme cold makes wiring insulation prone to cracking.

How to Talk to a Mechanic About This Code

Say this: "I have a P1703 code and my brake lights are [stuck on / not working]. I'd like a diagnostic focusing on the brake switch, its stop pad, and the related wiring. Please confirm the code definition for my specific vehicle first."

Guides the technician toward common fixes, prevents costly misdiagnosis, and addresses critical manufacturer-specific quirks.

Avoid saying:

• 'My check engine light is on, can you look at it?'
• 'Just fix whatever is wrong with the brakes.'
• 'I think it's a computer problem.'

Questions to ask before authorizing the repair:

• Did you check the brake pedal stop pad for damage?
• Did you check the 'Brake On/Off' status in live data?
• Can you show me where the wiring damage is?
• What is the warranty on the parts and labor?

Where to Take It: Dealer vs Independent vs Chain

• Dealer: Recommended only if the vehicle is under warranty or an independent shop confirmed a complex module failure.
  Best for: Vehicles still under warranty., Complex module failures requiring programming.
  Downsides: Highest labor rates., Inclined to replace entire assemblies rather than perform wiring repairs. (Typical cost: +50% vs. baseline)
• Independent Shop: Best fit for most P1703 scenarios. Quickly diagnoses and fixes common causes at a fair price.
  Best for: Out-of-warranty vehicles with common P1703 causes., Cost-effective diagnosis and wiring repairs.
  Downsides: Quality varies; ensure the shop has electrical diagnostic experience., Lacks dealer-specific programming tools. (Typical cost: +0% vs. baseline)
• Chain Shop: Acceptable for a straightforward switch replacement if you diagnosed the problem yourself. Avoid for initial diagnosis.
  Best for: Simple brake light switch replacements.
  Downsides: Technician skill varies dramatically., Struggles with wiring or manufacturer-specific issues., High pressure to upsell. (Typical cost: -10% vs. baseline)

When to Walk Away From the Repair

If the estimated repair cost exceeds 50% of your car's private-party value, evaluate your options.

• Car worth $4000, fix is $300: Fix it. This is a minor repair cost relative to the car's value.
• Car worth $3000, fix is $1800: Walk away. The repair cost is over 50% of the car's value.

What Scan Tool You Need for This Code

Minimum: An OBD-II scanner that reads live data, specifically the 'Brake On/Off' (BOO) PID.

Basic readers do not show switch status. Without live data, you cannot confirm if the computer sees the pedal being pressed.

Budget: BlueDriver Pro or ANCEL BD310 (~$100) — Connects via Bluetooth to view live data, including brake switch status.

Mid-range: Innova 5610 or Foxwell NT809BT (~$350) — Graphs data streams and accesses ABS/BCM modules.

Professional: Autel MaxiCOM MK808 (~$500-1200) — Offers full bidirectional control and advanced diagnostics for all modules.

Rent vs buy: AutoZone offers a 'Loan-A-Tool' program for a free rental.

How to Clear the Code After You Fix It

1. Use an OBD-II scan tool to clear the diagnostic trouble codes (DTCs).
2. Perform a complete drive cycle to allow the onboard diagnostic systems to re-run their tests.

Drive cycle (~20 minutes): Cold start, idle for 2 minutes, drive for 15 minutes with mixed city/highway conditions, pressing the brake pedal multiple times.

Readiness monitors affected: Comprehensive Component Monitor (CCM)

Before emissions retest: drive at least 50 miles to fully set monitors.

Watch out for:

• Clearing the code without fixing the root cause results in immediate return.
• Testing immediately after clearing fails readiness monitors.

Will This Fail Emissions / State Inspection?

Yes — this code typically fails an OBD-II emissions inspection.

• California: An illuminated Check Engine Light is an automatic failure of the smog inspection.
• New York: An active P1703 code and illuminated Check Engine Light causes the vehicle to fail.
• Texas: An illuminated Check Engine Light is an automatic failure. Unset readiness monitors also fail the test.

Most Commonly Affected Vehicles

• Ford F-150, F-250, F-350 (2011-2019) — Extremely common for the brake pedal stop pad to disintegrate, causing the switch plunger to be out of position.
• Ford Explorer, Expedition, Escape (2002-2017) — Widespread issues with the brake light switch failing internally.
• Ford Mustang (2005-2014) — Prone to brake light switch failures. Proper installation and adjustment are critical.
• Hyundai Sonata, Elantra (2006-2014) — CRITICAL: P1703 means 'Throttle Position Sensor (TPS) Low Input'. Symptoms are poor acceleration, not brake issues.
• Kia Sorento, Optima (2011-2015) — P1703 indicates a Throttle Position Sensor (TPS) fault. Verify the code definition before diagnosing brakes.
• BMW Various Models (E60, E90) (2005-2013) — Triggered by a faulty wheel speed sensor. The ABS module sees conflicting data and logs a fault.
• Mazda Tribute, CX-9 (2008-2012) — Shares platforms with Ford, making it susceptible to identical brake light switch and stop pad issues.
• Lincoln Navigator, MKX (2003-2017) — Uses identical electronic components to Ford, leading to frequent P1703 codes from switch or stop pad failure.

Manufacturer-Specific Notes

• Ford / Lincoln / Mazda: Uses the standard 'Brake Switch Out of Self-Test Range' definition. The crumbling brake pedal stop pad is a notoriously common cause.
• Nissan: P1703 means 'Transmission Control Module Unable to Access ROM'. This is a serious internal failure requiring TCM replacement.
• Subaru: P1703 indicates a 'Low Clutch Timing Control Solenoid Valve Circuit Malfunction', pointing to a transmission issue.
• Honda: On manual transmissions, P1703 means 'Clutch Switch Incorrect Correlation'. The PCM receives conflicting signals from clutch pedal switches.
• Hyundai / Kia: P1703 points to a 'Throttle Position Sensor (TPS) Low Input'. This causes acceleration problems, completely unrelated to brakes.
• General Motors (GM / Chevrolet): P1703 is defined as 'Pressure Switch "C" Circuit Low', which relates to a transmission fluid pressure switch.
• Chrysler / Dodge / Jeep: Uses P1703 to refer to a brake switch circuit malfunction, identical to Ford.

Real Owner Stories

2013 Ford F-150 with 110K miles

Check engine light illuminated. Brake lights were stuck ON, draining the battery. Cruise control was disabled.

What they tried:

1. Initially suspected a bad brake light switch and ordered a replacement.
2. While inspecting the brake pedal, found small blue plastic crumbles on the floor mat.
3. Discovered the brake pedal stop pad disintegrated, preventing the pedal from pressing the switch plunger.

Outcome: The owner installed a $10 Dorman replacement pad into the brake pedal arm. The original switch functioned perfectly, and all codes cleared.

Lesson: On Ford trucks, check for a failed brake pedal stop pad before replacing the switch. Finding plastic bits on the floor is the definitive giveaway.

2017 Hyundai Elantra with 50K miles

Car suffered poor acceleration, jerky shifting, and logged code P1703.

What they tried:

1. Owner searched P1703 online and found brake switch articles, but symptoms were engine-related.
2. Took the car to a shop where they confirmed the code definition for this Hyundai is 'Throttle Position Sensor (TPS) Low Input'.
3. The shop cleaned the throttle body, but the code returned.

Outcome: The Throttle Position Sensor failed. The entire throttle body assembly was replaced under warranty, resolving the performance issues.

Lesson: For Hyundai/Kia models, P1703 is a TPS code, not a brake switch code. Verify the code definition for your exact vehicle to avoid misdiagnosis.

2008 Ford F-150 V8

Owner ran a Key On Engine Running (KOER) self-test with a scan tool and a P1703 code appeared. There were no physical symptoms.

What they tried:

1. The owner posted on a forum for advice regarding a potential circuit fault.
2. Forum members explained the KOER self-test requires the driver to press the brake pedal when prompted.
3. The owner had not pressed the brake pedal during the sequence.

Outcome: The owner re-ran the KOER self-test and pressed the brake pedal correctly. The P1703 code did not return.

Lesson: A P1703 code triggers from user error during manual diagnostic self-tests. Follow the test procedure correctly before suspecting a part failure.

How to Prevent This Code From Triggering

• Inspect and clean the area around the brake pedal (Every 15,000 miles) — Dirt and debris contaminate the brake light switch, causing the mechanical plunger to stick.
• Apply dielectric grease to the brake light switch connector (When replacing the switch) — Dielectric grease blocks moisture from reaching the metal pins, preventing corrosion and high resistance.
• Use a silicone-based protectant spray on under-dash plastics (Every 2 years) — Silicone spray protects the brake pedal stop pad from drying out and crumbling due to temperature cycles.
• Ensure wire repairs use sealed connectors (During any electrical repair) — Adhesive-lined heat shrink tubing seals the connection from moisture, preventing future corrosion.

Frequently Asked Questions

Can I fix a P1703 code myself?

Yes, for common causes. Replacing a fuse, stop pad, or brake light switch are straightforward DIY repairs.

What is the most common misdiagnosis for P1703?

Replacing the switch on a Ford without checking for a broken plastic stop pad. Another is assuming the switch is good just because the brake lights work.

Why can't I shift out of Park with a P1703 code?

The shift interlock requires a brake switch signal to confirm your foot is on the pedal. A faulty switch denies this permission.

What is the 'brake switch self-test'?

The PCM automatically checks the brake switch voltage at startup. If it sees an 'on' signal without pedal pressure, the test fails and logs P1703.

I replaced the brake light switch, but the code came back. What now?

Check for a broken stop pad or verify the new switch is adjusted correctly. If both are fine, inspect the wiring harness for shorts.

How much does it cost to fix P1703?

Costs vary by cause. A fuse or stop pad costs under $15, while a new brake light switch runs $75-$200 including labor. Complex wiring or Hyundai TPS issues cost $150-$300+.

Can a bad battery cause a P1703 code?

Yes. Low voltage during startup causes self-tests to fail erratically, logging ghost codes. Test the battery if you experience slow cranking.

Key Takeaways

• On Ford, Lincoln, Mazda, and BMW vehicles, P1703 directly indicates a failed brake light switch or a broken pedal stop pad.
• Expect immediate physical symptoms including brake lights stuck on or off, disabled cruise control, and an inability to shift out of Park.
• Look for crumbled plastic pieces on the driver's floor mat before buying parts; a disintegrated $10 brake pedal stop pad is the leading cause on Ford trucks.
• Verify your specific vehicle's code definition immediately; on Hyundai and Kia models, P1703 flags a Throttle Position Sensor (TPS) failure, not a brake issue.