Code
C1550
Generic
C — Chassis
Brake pressure sensor circuit malfunction
Views:
UK: 6
EN: 4
RU: 4
AI status
Completed
Completed
100%
Causes
- Open or shorted wiring in the brake pressure sensor harness
- Corroded, loose, or damaged sensor connector
- Failed brake pressure sensor (hydraulic unit or in-line sensor)
- Faulty ABS/Brake control module or module ground
- Contamination or fluid intrusion at sensor or connector
- Intermittent connection due to chafing or broken wires
Symptoms
- ABS and/or brake warning light illuminated
- Traction/stability control warning lights may also be on
- Reduced or altered ABS operation during braking
- Stored/active fault codes related to brake pressure or ABS
- Possible change in brake pedal feel or unexpected ABS activation
What to check
- Scan for stored and pending codes, note freeze frame and freeze data
- Visually inspect sensor, harness, and connector for damage or fluid
- Backprobe sensor connector and check reference voltage and ground
- Measure signal voltage or resistance at sensor with ignition on
- Wiggle harness and connectors while monitoring live data for intermittent faults
- Perform continuity and short-to-power/ground tests on wiring to module
Signal parameters
- Sensor type: typically an analog pressure transducer (0–5 V) or resistive sensor
- Expected at rest (no pressure): approx. 0.5–1.0 V (varies by manufacturer)
- Expected at high brake pressure: approx. 4.0–4.5 V (varies by manufacturer)
- Reference supply: usually stable 5 V from ABS module
- Ground: low resistance to chassis ground (
- If sensor is frequency-based, expect a varying frequency proportional to pressure
Diagnostic algorithm
- Retrieve all ABS and related codes; record freeze frame and live data.
- Visually inspect sensor, connector and harness for corrosion, fluid, chafing or damage.
- With ignition ON (engine off), backprobe connector: verify stable reference voltage (≈5 V), good ground, and signal voltage. Note values.
- With a helper, press brake pedal while monitoring signal voltage; signal should change smoothly with pressure.
- If reference or ground is missing or noisy, trace/repair wiring to ABS module; check module grounds.
- Check continuity of signal wire to module and for shorts to power or ground. Repair any wiring faults.
- If wiring and supply are good but signal is out of range or inconsistent, replace the brake pressure sensor (or hydraulic control unit sensor).
- After repair, clear codes and road test to confirm proper operation and that code does not return.
- If fault persists with correct wiring and a new sensor, evaluate/replace ABS control module or perform further module-level diagnostics per manufacturer procedures.
- Safety note: Take care when working near hydraulic components; support vehicle and relieve pressure per service information before disconnecting hydraulic parts.
Likely causes
- Damaged or pinched harness near steering/suspension or hydraulic unit
- Corroded connector at the pressure sensor (common at low points)
- Failed sensor internal electronics (common in high-mileage units)
- Poor or missing sensor reference voltage (5 V) or ground from module
- Short to power or ground due to fluid leak into connector
Fault status
Status
Brake pressure sensor circuit malfunction — check sensor, wiring, and ABS module.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
Workshop Manuals
Available brands with manuals
1
LAND ROVER 2
Land Rover Defender 300Tdi — Workshop Manual (1996 model year)
Workshop ManualOfficial workshop manual for the Land Rover Defender 300Tdi (from 1996 model year). Contains specifications, adjustment, fault diagnosis and step-by-step repair and overhaul procedures for engine, transmission, axles, suspension, brakes, electrical and body. Intended for dealer workshops and trained technicians.
199,00 UAH
Land Rover Defender Workshop Manual Supplement & Body Repair Manual (1999 & 2002 MY)
Workshop ManualWorkshop Manual Supplement and Body Repair Manual for the Land Rover Defender. Includes general specifications, maintenance schedules, tuning data and step‑by‑step repair procedures for engine, transmission, suspension, brakes, electrical and body repairs. Covers Defender models from 1999 and 2002 model years.
199,00 UAH
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Code
C1550
OPEL
C — Chassis
Replace Electronic Control Unit (ECU)
Views:
UK: 4
EN: 6
RU: 3
AI status
Completed
Completed
100%
Causes
- Open or shorted wiring in the brake pressure sensor harness
- Corroded, loose, or damaged sensor connector
- Failed brake pressure sensor (hydraulic unit or in-line sensor)
- Faulty ABS/Brake control module or module ground
- Contamination or fluid intrusion at sensor or connector
- Intermittent connection due to chafing or broken wires
Symptoms
- ABS and/or brake warning light illuminated
- Traction/stability control warning lights may also be on
- Reduced or altered ABS operation during braking
- Stored/active fault codes related to brake pressure or ABS
- Possible change in brake pedal feel or unexpected ABS activation
What to check
- Scan for stored and pending codes, note freeze frame and freeze data
- Visually inspect sensor, harness, and connector for damage or fluid
- Backprobe sensor connector and check reference voltage and ground
- Measure signal voltage or resistance at sensor with ignition on
- Wiggle harness and connectors while monitoring live data for intermittent faults
- Perform continuity and short-to-power/ground tests on wiring to module
Signal parameters
- Sensor type: typically an analog pressure transducer (0–5 V) or resistive sensor
- Expected at rest (no pressure): approx. 0.5–1.0 V (varies by manufacturer)
- Expected at high brake pressure: approx. 4.0–4.5 V (varies by manufacturer)
- Reference supply: usually stable 5 V from ABS module
- Ground: low resistance to chassis ground (
- If sensor is frequency-based, expect a varying frequency proportional to pressure
Diagnostic algorithm
- Retrieve all ABS and related codes; record freeze frame and live data.
- Visually inspect sensor, connector and harness for corrosion, fluid, chafing or damage.
- With ignition ON (engine off), backprobe connector: verify stable reference voltage (≈5 V), good ground, and signal voltage. Note values.
- With a helper, press brake pedal while monitoring signal voltage; signal should change smoothly with pressure.
- If reference or ground is missing or noisy, trace/repair wiring to ABS module; check module grounds.
- Check continuity of signal wire to module and for shorts to power or ground. Repair any wiring faults.
- If wiring and supply are good but signal is out of range or inconsistent, replace the brake pressure sensor (or hydraulic control unit sensor).
- After repair, clear codes and road test to confirm proper operation and that code does not return.
- If fault persists with correct wiring and a new sensor, evaluate/replace ABS control module or perform further module-level diagnostics per manufacturer procedures.
- Safety note: Take care when working near hydraulic components; support vehicle and relieve pressure per service information before disconnecting hydraulic parts.
Likely causes
- Damaged or pinched harness near steering/suspension or hydraulic unit
- Corroded connector at the pressure sensor (common at low points)
- Failed sensor internal electronics (common in high-mileage units)
- Poor or missing sensor reference voltage (5 V) or ground from module
- Short to power or ground due to fluid leak into connector
Fault status
Status
Brake pressure sensor circuit malfunction — check sensor, wiring, and ABS module.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
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