P0703 - Brake Pedal Switch 'B'' Circuit
System
Powertrain (Engine & Gearbox)
Technical Description
The control module has detected a fault in the Brake Pedal Switch 'B'' Circuit (P0703).
Multimeter Test Points & Nominal Values
| Test Point / Component | Measurement | Nominal Target Range | Test Condition |
|---|---|---|---|
| Brake Pedal Switch 'B'' Circuit – Coil Resistance | Resistance (Ω) | 3 - 30 Ω (typical) | Connector disconnected at 20°C |
| Brake Pedal Switch 'B'' Circuit – Duty Cycle | PWM (%) | 5 - 95 % (modulates with target) | Engine running, actuator in control |
| Brake Pedal Switch 'B'' Circuit – Supply Voltage | Voltage (V) | 11.8 - 14.4 V | Ignition ON at connector |
Connector disconnected at 20°C
Engine running, actuator in control
Ignition ON at connector
Oscilloscope Waveform Analysis
2 ms/div, 20 V/divPossible Causes
Short to ground on the signal wire or an internal short circuit within Brake Pedal Switch 'B'' Circuit
Channel B:Verify dedicated wiring pins and signal pair for circuit B against the schematic.
Chafed or pinched wiring harness along the signal path to Brake Pedal Switch 'B'' Circuit
Internal mechanical wear or carbon deposits inside Brake Pedal Switch 'B'' Circuit
Defective internal output driver or reference circuit in the control module for Brake Pedal Switch 'B'' Circuit
Symptoms
Recommended Solution
Compare signal voltage and resistance between circuit B and companion circuit A at module connector.
Check wire insulation resistance to ground (< 1 Ω indicates harness pinched or chafed against engine block/chassis).
Verify loaded supply voltage and harness terminal pins at Brake Pedal Switch 'B'' Circuit.
Check circuit continuity and ground-side voltage drop (< 0.05 V) for Brake Pedal Switch 'B'' Circuit.
Check supply and the low-side driver at the ECM connector. Replace the actuator or repair the circuit based on the readings.
Mechanic's Tip
Use the scan-tool output test with the scope on the control side at the same time. If duty changes but the actuator does not move, the valve is stuck — not the electrical fault you were chasing.