Anti-lock brake system (ABS control unit)
P-44
brake fluid on the brake slave-pump of blocked wheel back to the line of brake master-pump and
decrease the pressure of brake slave-pump.
In the stage of EBD pressure reduction: Brake fluid flown back after stored in the accumulator, but, if
the accumulator has been filled up with the brake fluid, and the deceleration of rear wheels are still
faster than the front wheels, the ECU of ABS control unit controls the action of reflux pump, and pump
back the excessive brake fluid into the circuit of brake master-pump.
Faults of brake light switch
Faults Causes of failures Possible fault area
Brake switch
There are open-circuits or too high resistance in the
following lines:
1. Signal circuit of brake light switch,
2. Grounding circuit of brake light
3. Brake light
1. Brake light switch
2. Circuit of brake light switch
3. Plugging-in of brake light
switch;
4. ABS control unit grounding;
5. ABS control unit with
hydraulic pressure regulator;
The brake light switch is a constant open switch. When the brake pedal stepped down, this switch is
close. The brake light switch will provide the brake light signal circuit (+BLS) with the signal voltage.
The ECU of ABS control unit supervises the signal voltage of brake light switch, so as to confirm the
coupling time of brake and test the circuit of brake light switch.
Recommendation: Check the harness of brake light switch.
The ABS control unit shall not be replaced.
ECU faults
DTC DTC(16 hex)
Potential failure
symptom
Description of DTC
C1900 0x5900 0100 ECU voltage too high
C1901 0x5901 0100 ECU voltage too low
C1000 0x5000 0100 HW fault in the ECU
Recommendation: Check the battery and the level of voltage.
The ABS control unit shall not be replaced.
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