Toyota Tacoma 2015-2018 Service Manual: Brake Booster Pump Motor on Time Abnormally Long (C1252)

DESCRIPTION

The motor relay (semiconductor relay) is built into the master cylinder solenoid and drives the pump motor based on a signal from the skid control ECU (master cylinder solenoid).

WIRING DIAGRAM

CAUTION / NOTICE / HINT

HINT:

When C1253, C1254 or C1256 is output together with C1252, inspect and repair the trouble areas indicated by C1253, C1254 or C1256 first.

PROCEDURE

(a) Turn the ignition switch to OFF.

(b) Depress the brake pedal more than 20 times.

(c) Turn the ignition switch to the ON position.

(d) Check how the hydraulic brake booster pump motor operates.

B

REPLACE HYDRAULIC BRAKE BOOSTER

C

GO TO STEP 4

D

GO TO STEP 5

A

(a) Using a screwdriver, remove the 2 plugs from the hydraulic brake booster (See page ).

(b) Check the tightening torque of 2 screws which fasten the wire harness connecting hydraulic brake booster and brake booster pump (See page ).

Torque:

2.9 N·m {30 kgf·cm, 26 in·lbf}

NG

RETIGHTEN SCREWS

OK

(a) Using a screwdriver, remove the 2 screws and pull the wire harness from the hydraulic brake booster assembly.

(b) Measure the resistance between the red wire (MT+) and black wire (MT-).

Resistance:

2 Ω

NG

REPLACE HYDRAULIC BRAKE BOOSTER

OK

(a) Connect Techstream to the DLC3.

(b) Turn the ignition switch to the ON position.

(c) Turn Techstream ON.

(d) Select the Data List mode on the Techstream.

(e) Check that the accumulator pressure sensor output is normal.

B

REPLACE MASTER CYLINDER SOLENOID

C

REPLACE HYDRAULIC BRAKE BOOSTER

A

(a) Clear the DTCs (See page ).

(b) Turn the ignition switch to OFF.

(c) Turn the ignition switch to the ON position.

(d) Wait for more than 5 minutes.

(e) Check if the same DTCs are recorded.

A

REPLACE MASTER CYLINDER SOLENOID

B

REPLACE HYDRAULIC BRAKE BOOSTER