Toyota Camry 1999 Electrical Troubleshooting Manual page 234

ABS (TMC MADE)
SYSTEM OUTLINE
This system controls the respective brake fluid pressures acting on the disc brake cylinders of the right front wheel, left front
wheel and rear wheels when the brakes are applied in a panic stop so that the wheels do not lock. This results in improved
directional stability and steerability during panic braking.
1. INPUT SIGNALS
(1) Speed sensor signal
The speed of the wheels is detected and input to TERMINALS FL+, FR+, RL+ and RR+ of the ABS ECU.
(2) Stop light SW signal
A signal is input to TERMINAL STP of the ABS ECU when the brake pedal is depressed.
2. SYSTEM OPERATION
During sudden braking the ABS ECU has signals input from each sensor, which controls the current to the solenoid inside
the actuator and lets the hydraulic pressure acting on each wheel cylinder escape to the reservoir. The pump inside the
actuator is also operating at this time and it returns the brake fluid from the reservoir to the master cylinder, thus preventing
locking of the vehicle wheels.
If the ABS ECU judges that the hydraulic pressure acting on the wheel cylinder is insufficient, the current on the solenoid is
controlled and the hydraulic pressure is increased. Holding of the hydraulic pressure is also controlled by the ABS ECU, by
the same method as above. Pressure reduction, holding and increase are repeated to maintain vehicle stability and to
improve steerability during sudden braking.
SERVICE HINTS
A9, A10 ABS SPEED SENSOR FRONT LH, RH
2–1 : 0.6 kΩ–2.5 kΩ
A25, A26 ABS SPEED SENSOR REAR LH, RH
2–1 : 1.2 kΩ–2.3 kΩ
A18 (A), A19 (B) ABS ECU
(Connect the ABS ECU connectors)
(B)21–GROUND : Approx. 12 volts with the ignition SW at ON position and the data link connector 1
TS–E1, TC–E1 not connected
(B) 8–GROUND : Approx. 12 volts with the ignition SW at ON position and the data link connector 1
TS–E1, TC–E1 not connected
(B)13–GROUND : Approx. 12 volts with the ignition SW at ON position
(B) 5–GROUND : Approx. 12 volts with the brake pedal depressed
(B)12, (B) 25–GROUND :
Always continuity
: PARTS LOCATION
Code See Page
26 (1MZ–FE)
A4 A4 A A
28 (5S–FE)
26 (1MZ–FE)
A5 A5 B B
28 (5S–FE)
26 (1MZ–FE)
A9 A9
28 (5S–FE)
26 (1MZ–FE)
A10 A10
28 (5S–FE)
A18 A 30
A19 B 30
: RELAY BLOCKS
Code See Page
3 25
Code
A25
A26
C10
D1 D1
D4
J3
J4
J7 A
J8 B
Relay Blocks (Relay Block Location)
Engine Room R/B No.3 (Radiator Upper Support RH)
See Page
32
32
30
26 (1MZ–FE)
28 (5S–FE)
30
31
31
31
31
Code See Page
J11 31
J12 31
J22 31
J23 31
J27 A 31
J28 B 31
J29 31
S6 31