Fault code description
Brake pressure sensor – electrical fault in the circuit
An error code stored in the ESP system for driving dynamics control, “Brake pressure sensor – electrical fault in the circuit,” indicates a defect in the brake pressure sensor in the hydraulic unit of the ESP system. A lack of pressure information leads to the deactivation of the ESP function and a restriction of the ABS control.
ESP systems are further developments based on ABS systems with EBV and ASR functions. They can adjust wheel brake pressures individually and intervene in torque control via the drive control system. The pressure sensors provide important information for control and thus for pressure modulation of the ESP hydraulic unit.
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System description:
Pressure sensors are components of an electronic stability program. Their signals serve as input information for the ESP control unit regarding the pressure in the hydraulic unit. For driving dynamics systems that intervene in the hydraulic brake system, it is necessary to measure the pressure built up in the system. The pressure in the main brake circuit is measured to determine the braking force requested by the driver.
Fault code „Brake pressure sensor – electrical fault in the circuit“ Error description:
The ESP control unit monitors the plausibility and the current deviation from the setup pressure in the signal circuit. The setup basis is the pressure in the system without the brake pedal being pressed at the start of an „ignition on“ cycle. Feedback to the secured brake pedal position is provided by the brake pedal/brake light switch. If the values in the setup are not reached, the error is set.
To achieve durability, the brake pressure sensor contains two measuring cells that operate independently of each other. Both measured values are compared in the add-on control unit. If there is a significant deviation, the control unit sets the pressure value to a default value that is above the error detection threshold. The parameter/actual value shown is above the technically plausible pressure, which indicates a defective pressure sensor.
Possible causes:
- Faulty internal brake pressure sensor in the hydraulic unit
- Calibration error in the brake pressure sensor
- Faulty or incorrectly adjusted brake pedal/brake light switch
Consequences of the error:
To prevent faulty ESP control interventions, the ESP functions are deactivated.
The control indicator for the driving dynamics control and the fault indicator for the anti-lock braking system light up continuously.
The ABS system can perform its basic function with a pressure calculation model, but its functionality is therefore limited.
The vehicle can be driven, but the ABS system is not available.
Possible emergency strategy for driving dynamics control:
- Deactivation of the ESP function
- Restriction of the ABS control system
Exemplary representation of the diagnosis-relevant parameters of a defective brake pressure sensor with significantly deviating brake pressure.
Diagnosis/measurements/repair:
Reading the brake pressure value from the parameters of the ESP control unit.
With the ignition switched on, the brake pressure displayed must be between -1.5 and +1.5 bar when the brake pedal is not depressed. On some systems, between -1.0 and +1.0 bar.
Ensure in the relevant control units that the brake pedal/brake light switches indicate the correct zero position and that there are no faults in the brake light control. In the event of a fault, the settings and calibrations must be made before further repairs are carried out. A new test run should reproduce the fault.
We repair MK60 Engine control unit following vehicle manufacturer in connection with this error.
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