P1703

What Does Code P1703 Mean?

Diagnostic Trouble Code (DTC) P1703 signifies that the Powertrain Control Module (PCM), or in some vehicle architectures the Transmission Control Module (TCM), has detected an inconsistency or implausible signal from the Brake Pedal Position (BPP) switch during its self-test routines. The primary function of the BPP switch is to signal the PCM whether the brake pedal is currently engaged or disengaged. This input is critical for various vehicle systems including cruise control operation, torque converter clutch (TCC) engagement/disengagement, transmission shift scheduling, and often the shift interlock system. The “Out Of Self Test Range” descriptor indicates that the PCM, during a specific diagnostic cycle (e.g., key-on self-test, or while monitoring brake application during driving conditions), did not receive the expected signal transition, voltage level, or continuity from the BPP switch. This typically means the switch is either stuck in one position (open or closed), providing an intermittent signal, or its signal falls outside the programmed parameters the PCM expects to see for a properly functioning brake switch.

Common Symptoms

• Inoperative or Intermittent Cruise Control: The most common symptom, as the PCM uses the brake switch input to disengage cruise control.
• Transmission Shifting Irregularities: May include harsh shifts, delayed upshifts, or the torque converter clutch failing to engage or disengage correctly.
• Inability to Shift Out of Park: If the BPP switch signal is also used for the shift interlock solenoid, a faulty switch can prevent shifting from Park.
• Constant or Intermittent Brake Lights: While often a separate set of contacts, a faulty BPP switch can sometimes affect brake light operation, causing them to be stuck on or off.
• Illumination of the Malfunction Indicator Lamp (MIL): The Check Engine Light will illuminate as P1703 is a stored DTC.
• Engine Stalling or Hesitation: In some instances, incorrect brake switch input can interfere with engine idle strategy or fuel cut-off during deceleration, leading to minor performance issues.

What Causes the Code P1703?

• Faulty Brake Pedal Position (BPP) Switch: The most frequent cause. Internal electrical contacts can wear out, corrode, or experience mechanical failure, leading to an inconsistent or stuck signal.
• Damaged or Corroded Wiring Harness: Open circuits, short circuits to voltage or ground, or high resistance in the wiring between the BPP switch and the PCM. This often occurs at connector points due to moisture intrusion or vibration.
• Improperly Adjusted Brake Switch: If the BPP switch plunger or contact point is not correctly aligned with the brake pedal arm, it may not actuate at the correct pedal travel, resulting in an “out of range” signal.
• Blown Fuse: A less common cause, but if the BPP switch circuit has a dedicated fuse for its power supply and it’s blown, the switch will not receive power, leading to an incorrect signal.
• PCM/TCM Internal Fault: Extremely rare, but possible if the input circuit within the control module itself is damaged or malfunctioning. This should only be considered after all other possibilities have been exhaustively ruled out.

How to Diagnose and Troubleshoot

Diagnosis of P1703 requires a methodical approach, utilizing an OBD-II scanner, a digital multimeter (DMM), and visual inspection:

1. Retrieve and Analyze DTCs and Freeze Frame Data: Connect an OBD-II scanner and record all stored DTCs and associated freeze frame data. Freeze frame data provides crucial information about engine parameters at the time the code was set, which can help replicate conditions.
2. Monitor Live Data for BPP Switch: Use the OBD-II scanner to monitor the live data stream for the Brake Pedal Position (BPP) or Brake Switch PID. Observe its state (typically displayed as ON/OFF, Pressed/Released, or a voltage value) while manually pressing and releasing the brake pedal. The PID should show a clear and consistent transition between states. If it remains stuck ON or OFF, or fluctuates erratically, the switch or its circuit is faulty.
3. Visual Inspection of the BPP Switch and Wiring: Locate the BPP switch, typically mounted on the brake pedal arm under the dashboard. Inspect it for physical damage, loose mounting, or misalignment. Trace the wiring harness leading to the switch and its connector. Look for frayed wires, exposed conductors, signs of rubbing, or corrosion at the connector terminals.
4. Digital Multimeter (DMM) Testing of the BPP Switch:
   • Power and Ground Check: Disconnect the BPP switch connector. Using a wiring diagram specific to the vehicle, identify the power and ground terminals. With the ignition ON, verify approximately 12V at the power terminal and a solid ground at the ground terminal.
   • Switch Continuity/Resistance Test (Disconnected): With the switch disconnected from the harness, use the DMM in continuity or resistance mode across the switch’s signal terminals. As you manually actuate the switch (simulating pedal press/release), the meter should show a clear change from open to closed (or vice-versa), indicating proper internal contact operation. For switches that output a variable resistance or direct voltage, consult repair data for expected values.
   • Switch Output Voltage Test (Connected): If the switch outputs a voltage signal, backprobe the signal wire at the switch connector (with the switch connected and ignition ON). Observe the voltage as the brake pedal is pressed and released. It should cleanly switch between two distinct voltage levels (e.g., 0V to 12V, or 0V to 5V).
5. Wiring Harness Continuity and Short Test: If the BPP switch tests good, disconnect both the switch and the PCM/TCM connectors. Use the DMM to test continuity of each wire from the BPP switch connector to its corresponding pin at the PCM/TCM connector. Look for high resistance, open circuits, or short circuits to ground or power in the wiring.
6. Brake Switch Adjustment Check: For adjustable BPP switches, ensure it is correctly positioned. Some switches thread into a bracket and are adjusted by rotation, others use a push-in design that self-adjusts or has a specific installation procedure to ensure proper contact with the brake pedal arm.

Recommended Repairs and Solutions

Once the diagnostic steps have identified the root cause, the following repairs are typically recommended:

1. Replace the Brake Pedal Position (BPP) Switch: This is the most common resolution for P1703. Ensure the replacement switch is an OEM-equivalent part to guarantee proper functionality and longevity. When installing, follow manufacturer-specific procedures for adjustment, if applicable.
2. Repair or Replace Damaged Wiring/Connectors: If the DMM tests or visual inspection revealed issues with the wiring harness or connectors, perform precise repairs. This involves splicing in new wire sections using proper solder and heat shrink methods, or replacing corroded connector terminals. Avoid quick fixes that may lead to future intermittent problems.
3. Adjust the Brake Switch: If the BPP switch itself tests electrically sound but was found to be improperly adjusted, correct its position according to the vehicle service manual. This ensures the switch actuates and de-actuates at the appropriate brake pedal travel.
4. Clear DTCs and Perform a Test Drive: After any repair, use the OBD-II scanner to clear the P1703 code and any other related DTCs. Perform a comprehensive test drive under varying conditions, including multiple brake applications and cruise control engagement, to verify the repair. Re-scan for codes to ensure the P1703 does not return.
5. PCM/TCM Replacement or Reprogramming: This is a last resort and should only be considered if all other components and wiring have been meticulously tested and confirmed to be in perfect working order. A faulty control module typically manifests with multiple, seemingly unrelated issues, not just a single sensor input problem.