System Testing: Notes

NOTE: Inoperative HBB cannot cause noisy brakes, fading brake pedal or pulling brakes. If any of these conditions exist, other components of brake system are at fault.

NOTE: Hydraulic Brake Booster (HBB) accumulates high-pressure oil in accumulator by activation of pump motor to assist braking power. Motor operation sounds are normal and not and indication of system failure.

SYMPTOM INDEX

Symptom

Perform Test

Communication Between Scan Tool & Communications Network Not Possible

⁽¹⁾

Communication Between Scan Tool & ABS-ECU Not Possible

⁽²⁾

Brake Warning Light Does Not Illuminate After Ignition Is Turned On Just After Engine Start

TEST 1

Brake Warning Light Remains Illuminated After Engine Is Started

TEST 2

DTC 53, 55 Or 57 Is Set, But Buzzer Does Not Sound

TEST 3

Buzzer Does Not Stop Sounding

TEST 4

⁽¹⁾	See MODULE COMMUNICATIONS NETWORK - MONTERO article.

⁽²⁾	See ANTI-LOCK BRAKES - MONTERO article.

Scan tool (MB991502) activates specified actuators for testing. See ACTUATOR TEST REFERENCE table.

NOTE: If M-ASTC-ECU is inoperative, actuator testing cannot be performed. Actuator testing is only possible when vehicle is stationary.

ACTUATOR TEST REFERENCE

Scan Tool Display	No.	Item	Drive Content	Activation When System Fails
HBB MOTOR	11	Pump Motor	Drives Pump Motor For One Second	Disabled
HBB BUZZER	12	Buzzer	Drives Buzzer For 3 Seconds	Disabled
BRKE WARN LMP	23	Brake Warning Light	Illuminates Brake Warning Light	Enabled (Disabled When Brake Warning Light Can Not Be Activated