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Home / DTC / C0637 — Brake Pressure Sensor G Circuit Low

C0637 — Brake Pressure Sensor G Circuit Low

Detailed page for trouble code C0637.

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C0637

Generic C — Chassis

Brake Pressure Sensor G Circuit Low

Brand: Generic
Type: C — Chassis
Views: UK: 16 EN: 21 RU: 20
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Page language: EN

Causes

  • Short to ground in the sensor signal wire
  • Open or damaged wiring/connector between sensor G and ABS/brake module
  • Corroded, bent, or loose connector pins at sensor or module
  • Failed brake pressure sensor G (internal short or open)
  • Faulty ABS/brake control module (rare)
  • Intermittent connector contact or water ingress

Symptoms

  • ABS and/or traction control warning lamp illuminated
  • Brake system warning light may illuminate
  • ABS/ESC functions reduced or disabled
  • Possible diagnostic trouble codes stored for other brake pressure sensor circuits
  • No obvious change in pedal feel in many cases (depends on vehicle)

What to check

  • Read and record all stored codes and freeze frame data with a scan tool
  • Visual inspection of wiring harness and connector at brake pressure sensor G and ABS module
  • Check connector for corrosion, bent pins, moisture, or poor mating
  • Backprobe the sensor connector to measure signal and reference voltages with ignition ON (engine off unless otherwise specified)
  • Measure continuity to ground of the sensor signal wire to check for shorts
  • Check reference voltage and ground at the sensor (compare to vehicle specification)

Signal parameters

  • Sensor type: brake pressure (typically a variable voltage sensor or pressure transducer)
  • Reference voltage (nominal): approx. 5.0 V (verify factory spec for vehicle)
  • Expected signal range: typically 0.5–4.5 V depending on pressure; exact idle/rest value varies by design
  • Low-circuit condition: signal voltage near 0 V or below module threshold (often
  • Resistance checks (if service manual provides): compare sensor element Ohms to spec

Diagnostic algorithm

  1. Safety: Park on level ground, engage parking brake, use wheel chocks, and follow manufacturer safety procedures.
  2. Clear codes and perform a test drive or cycle ignition to verify C0637 returns and capture freeze-frame data.
  3. Perform a visual inspection of the brake pressure sensor G connector and harness for damage, corrosion, or pin issues.
  4. Backprobe the sensor connector with key ON and measure: reference voltage, signal voltage, and ground. Compare to specifications. If signal is low (
  5. Unplug the sensor and measure the harness-side signal wire resistance to chassis ground. A near-zero reading indicates a short to ground; open/very high indicates open circuit.
  6. If short to ground is present, inspect wiring harness along route for damage, repair insulation or replace harness as required. If open, locate and repair splice/connector or replace wire.
  7. If wiring checks good (no short/open) but signal still low when sensor connected, bench-test or replace the brake pressure sensor G and verify output meets spec.
  8. If new sensor and harness test good but code persists, test ABS/brake control module grounds and reference supply. Consult wiring diagrams and perform module connector pin tests.
  9. Use an oscilloscope if available to view signal waveform during application of hydraulic pressure (if applicable) to confirm sensor behavior under load.
  10. After repairs, clear codes and verify repair with a road test and re-scan to ensure C0637 does not return.

Likely causes

  • Damaged or chafed signal wire shorted to ground
  • Corroded/poor connector at the pressure sensor
  • Failed pressure sensor element (internal short/open)
  • Bad ground at module or sensor harness

Fault status

⚠️ Status
Brake Pressure Sensor G Circuit Low — the brake system control module detects the sensor signal is below the expected voltage range. Inspect sensor, wiring, and module grounds/references.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours
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