Code
C1296
HUMMER
C — Chassis
Brake Fluid Pressure Sensor Circuit
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UK: 15
EN: 23
RU: 12
AI status
Completed
Completed
100%
Causes
- Damaged or corroded wiring harness or connector at the brake fluid pressure sensor
- Bad sensor (internal open, short, or failed output)
- Poor or missing ground or reference supply to the sensor
- Low or contaminated brake fluid causing sensor malfunction
- Intermittent connection (water intrusion, pin corrosion, broken wire)
- Faulty ABS/Brake control module or module software fault
Symptoms
- ABS warning light and/or Brake warning light illuminated
- Traction control/ESP light may also be on
- Diagnostic trouble codes stored in ABS/brake module
- Possible reduced braking system functionality or limp-home behavior (depending on system)
- Intermittent or constant false pressure readings in live data
- Unusual brake pedal feel in some failure modes
What to check
- Retrieve all ABS/brake module codes and freeze-frame/live-data with a scan tool
- Visually inspect sensor connector, wiring harness, and routing for damage, corrosion, or water intrusion
- Verify brake fluid level and condition; look for contamination or air in system
- Check fuses and relays related to the ABS/brake control module
- Backprobe sensor connector to verify reference voltage, ground continuity, and signal voltage
- Wiggle harness and connector while watching live data for intermittent changes
Signal parameters
- Sensor typically uses an electronic pressure transducer with a reference supply (commonly 5 V) and ground
- Expected signal is a variable voltage proportional to fluid pressure (typical range ~0.5–4.5 V, low at rest, higher with pressure)
- At Key On (engine off) signal may sit near the low end (sensor dependent) and should not be open or shorted to supply/ground
- Continuity from sensor ground to chassis ground should be near 0 Ω; reference supply should be stable at ~5 V (vehicle dependent)
- Specific ranges vary by model year; consult service manual for exact values before replacing parts
Diagnostic algorithm
- Connect a capable scan tool and record all ABS/brake codes and live-data values for brake fluid pressure sensor.
- Visually inspect the sensor, connector, and wiring for damage, corrosion, or fluid contamination. Repair any obvious issues.
- Check brake fluid level and condition; top or replace fluid if contaminated and clear air from system per procedure.
- With ignition on (engine off), backprobe the sensor connector: verify reference voltage (approx. 5 V), sensor ground, and signal voltage. Compare to expected values.
- With wiring accessible, perform continuity and short-to-power/short-to-ground checks between the sensor and ABS module connector pins with the harness disconnected.
- Wiggle the harness/connector while monitoring live-data to detect intermittent faults. Repair broken wires or poor terminals.
- If wiring and supplies are good, apply hydraulic pressure (hand pump or normal operation) and observe signal change. If signal does not change proportionally, replace the sensor.
- After repairs replace/clean connectors and secure harness; clear codes, perform key-on self tests, and road test to confirm the fault does not return.
- If fault persists and wiring is confirmed good, suspect ABS/brake control module failure and follow manufacturer procedures for module testing or replacement (do not replace module without proper bench/module-level diagnostics).
Likely causes
- Corroded or loose connector at the sensor
- Broken or shorted sensor supply or signal wire (chafing, pinched)
- Failed pressure sensor
- Bad ground at sensor or module
- Contaminated brake fluid or mechanical failure affecting the sensor
Fault status
Status
Brake fluid pressure sensor circuit fault detected by the ABS/brake control module. The sensor signal is open, shorted, out-of-range, or otherwise implausible.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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