Code
C1658
HUMMER
C — Chassis
Brake Pressure Sensor 'B' Circuit Range/Performance
AI status
Completed
Completed
100%
Causes
- Failed/bracketed brake pressure sensor (Sensor B)
- Open, shorted, or damaged wiring harness to sensor (signal, reference, ground)
- Corroded or loose connector pins
- Poor sensor ground or module ground
- Low battery or intermittent VREF to sensor
- Internal ABS/ESP module fault or input circuit failure
Symptoms
- ABS, traction control, or stability warning lamp illuminated
- Possible reduced functionality of ABS/ESC systems
- Brake pedal feel may be abnormal under ABS/ESC events (may not be noticeable all the time)
- Diagnostic trouble code stored (C1658) and freeze frame data may be present
- Inconsistent or unexpected behavior during braking/ABS events
What to check
- Read codes and freeze frame with manufacturer-level scan tool; record live data for Brake Pressure Sensor B
- Visual inspection of sensor, connector, and harness for damage, corrosion or fluid contamination
- Wiggle test harness while monitoring live data to detect intermittent opens/shorts
- Verify battery voltage and VREF supply to the sensor (typically from module; check ~5 V as a general reference)
- Measure sensor signal voltage at key states (rest, applied pedal, with pressure applied) and compare to expected behavior
- Check continuity and resistance of signal and ground circuits back to ABS module
Signal parameters
- Circuit type: typically 3-wire (VREF / Signal / Ground) to ABS/ESC module
- Typical reference supply: ~5 V (manufacturer dependent) — verify with reference data
- Typical signal output range for pressure sensors: roughly 0.5–4.5 V corresponding to low-to-high pressure (manufacturer dependent)
- Sensor impedance and exact voltage-to-pressure mapping are model-specific — consult service manual for exact values
- Signal should change smoothly with brake pressure; abrupt jumps, stuck values, or open/short conditions indicate fault
Diagnostic algorithm
- Connect a capable scan tool, record the DTC, freeze frame and live data for Brake Pressure Sensor B.
- Clear the code and attempt to reproduce; if code returns, continue diagnostics.
- Perform a visual inspection of the sensor, connector, and harness for damage, contamination, or fluid leaks.
- With ignition ON (engine off or as specified by service data), backprobe the sensor connector and verify VREF, ground continuity, and signal voltage. Compare to typical ranges (see signal_params).
- Operate the brake system (apply pedal or use a pressure source per service manual) while monitoring signal voltage — confirm signal varies smoothly with pressure.
- Check continuity and resistance from the sensor connector to the ABS module pins; look for opens, high resistance, or shorts to ground/battery.
- Perform a wiggle test on the harness and connectors while watching live data to catch intermittent faults.
- If wiring and connectors test good, swap with a known-good sensor (if available) or bench-test the sensor per factory procedure.
- If replacement sensor does not clear the issue, inspect ABS/ESC module inputs, grounds and update/reflash module software if service bulletins advise.
- After repairs, erase codes and perform a road test with the scan tool to verify correct operation and confirm the code does not return.
Likely causes
- Damaged wiring or poor connector at the sensor (most common)
- Failed pressure sensor (internal drift, short, or open)
- Bad ground or missing reference voltage to the sensor
- Faulty ABS/ESC control module input circuit
- Contaminated sensor from brake fluid leak or mechanical damage
Fault status
Status
Brake Pressure Sensor B circuit is reporting a signal outside expected range or not responding correctly. This can cause ABS/traction/stability warnings and may limit braking system functionality until the fault is resolved.
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
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