Code
C1298
Generic
C — Chassis
Brake Hydraulic Pressure Sensor Circuit Range/Performance
Views:
UK: 0
EN: 6
RU: 1
AI status
Completed
Completed
100%
Causes
- Faulty brake hydraulic pressure sensor
- Open, shorted or damaged wiring in sensor circuit
- Poor, corroded or loose connector/terminal at sensor or ABS module
- Loss of hydraulic pressure (leak, low fluid, air in system) producing out-of-range reading
- ABS/ESP module internal fault or poor ground
- Incorrect sensor calibration or software fault
Symptoms
- ABS warning lamp illuminated
- Brake warning lamp or traction control lamp may also illuminate
- ABS/traction control disabled or operating in limp mode
- Possible multiple ABS/pressure-related trouble codes stored
- Brake pedal feel usually unchanged with ABS disabled (may vary if hydraulic fault present)
What to check
- Retrieve freeze-frame and full trouble code list with a scan tool; note related codes and conditions
- Perform a visual inspection of the sensor, connector and wiring for damage, corrosion, moisture or loose terminals
- Check brake fluid level and inspect hydraulic lines and connections for leaks
- With ignition ON (engine off), use scan tool to view live data for brake pressure sensor output while applying brake pedal
- Backprobe sensor connector: verify reference voltage (usually a regulated reference) and ground present per service manual
- Measure sensor output voltage/resistance while slowly applying the brake pedal or using a calibrated pressure source; compare to expected values
Signal parameters
- Typical analog sensors use a regulated reference (commonly 5 V) with a signal output roughly in the 0.5–4.5 V range depending on pressure (0 V/near 0.5 V = no/low pressure; higher pressure → higher voltage). Exact voltages vary by design—consult OEM spec.
- Some systems use a frequency- or digital-type sensor; expected signal type and ranges must be verified from the vehicle service manual or scan tool data
- Measure reference voltage, signal voltage and ground continuity at the connector; compare to OEM values before replacing components
Diagnostic algorithm
- Connect a diagnostic scan tool, read/record C1298 and any related codes and freeze-frame data. Note ignition state and pedal position.
- Visually inspect sensor, harness and ABS module connector for damage, corrosion or water ingress. Repair any obvious issues.
- Check brake fluid level and look for external hydraulic leaks; top up if low and bleed if air suspected.
- With key ON engine OFF, backprobe sensor connector: verify reference voltage (per OEM), signal wire voltage and ground. Record values.
- Apply pedal (or use pressure tool) while watching live data and measuring sensor output voltage. Confirm output changes smoothly and remains within expected range.
- If signal is stuck, noisy, intermittent, or out of range and reference/ground are correct, disconnect and measure sensor resistance or bench-test per service procedure. Replace sensor if out of spec.
- If sensor tests OK, check continuity and resistance of wiring to the ABS module; repair open/shorts, corrosion or chafing as needed.
- After repairs or sensor replacement clear codes and perform a road/AEB/ABS functional test; monitor for code return. If wiring and sensor are good and fault persists, follow module diagnosis steps in the OEM manual (may require module reprogramming or replacement).
Likely causes
- Failed pressure sensor
- Damaged or corroded connector/wiring (intermittent or short to power/ground)
- Missing/unstable reference voltage or ground at sensor
- Hydraulic issue causing abnormal pressure signal
Fault status
Status
Brake hydraulic pressure sensor circuit — range/performance fault. ABS/ESP/traction functions may be disabled. Diagnostic testing of sensor, wiring and module required.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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