BRAKE SYSTEM WARNING LIGHT TURNS ON [ELECTRONICALLY CONTROLLED BRAKE SYSTEM]

id040309070500

Outline

Description	Brake system warning light turns on
Possible cause	•  Brake fluid level is low •  Brake fluid level sensor stuck on •  Short to ground in brake fluid level sensor signal circuit •  Electronically controlled brake unit connector is disconnected (circuit that turns on ABS warning light, TCS/DSC operation indicator light, brake system warning light, and TCS OFF indicator light if electronically controlled brake unit connector is disconnected) •  Electronically controlled brake unit detects malfunction (input/output device malfunction) •  Electronically controlled brake unit detects decrease in power supply voltage •  Poor ground in electronically controlled brake unit (If electronically controlled brake unit ground is not secured properly, ABS warning light, TCS/DSC operation indicator light, brake warning light, and TCS OFF indicator light turn on, but no DTC is output) •  Electronically controlled brake unit does not activate •  Electronically controlled brake unit internal malfunction •  Instrument cluster malfunction

Diagnostic Procedure

Step	Inspection	Results	Action
1	VERIFY BRAKE FLUID LEVEL •  Verify the brake fluid level. (See BRAKE FLUID INSPECTION.) •  Is the brake fluid level normal?	Yes	Go to the next step.
		No	Add brake fluid. •  Inspect the brake line for fluid leakage. If there is a malfunction, repair the malfunctioning location. Perform the repair completion verification.
2	VERIFY ELECTRONICALLY CONTROLLED BRAKE UNIT DTCs •  Verify the electronically controlled brake unit DTCs. (See DTC INSPECTION.) •  Is a DTC displayed?	Yes	Repair the malfunctioning location according to the applicable DTC troubleshooting. (See DTC TABLE [ELECTRONICALLY CONTROLLED BRAKE UNIT].)
		No	Communication error is displayed on M-MDS screen: •  Go to the next step. Communication error is not displayed on M-MDS screen: •  Go to Step 4.
3	INSPECT CONNECTION CONDITION FOR ELECTRONICALLY CONTROLLED BRAKE UNIT CONNECTOR •  Verify the connection condition of the applicable connector. (See CONNECTOR INSPECTION.) •  Is the applicable connector connected correctly?	Yes	Go to the next step.
		No	Connect the electronically controlled brake unit correctly again, then go to the next step.
4	VERIFY IF BRAKE SYSTEM WARNING LIGHT IS TURNED ON •  Switch the main power ON (READY off or on). •  Release the parking brake. •  Does the brake system warning light turn off?	Yes	Go to Step 7.
		No	Go to the next step.
5	INSPECT BRAKE FLUID LEVEL SENSOR FOR MALFUNCTION •  Inspect the applicable part. (See BRAKE FLUID LEVEL SENSOR INSPECTION.) •  Is the part normal?	Yes	Go to the next step.
		No	Replace the malfunctioning location and perform the repair completion verification. (See ELECTRONICALLY CONTROLLED BRAKE UNIT REMOVAL/INSTALLATION [L.H.D.].) (See ELECTRONICALLY CONTROLLED BRAKE UNIT REMOVAL/INSTALLATION [R.H.D.].)
*6	INSPECT BRAKE FLUID LEVEL SENSOR SIGNAL CIRCUIT FOR SHORT TO GROUND •  Inspect the applicable circuit for a short to ground. (See CIRCUIT INSPECTION.) •  Is the circuit normal?	Yes	Replace the instrument cluster and perform the repair completion verification.
		No	Repair or replace the malfunctioning location and perform the repair completion verification.
*7	INSPECT ELECTRONICALLY CONTROLLED BRAKE UNIT POWER SUPPLY CIRCUIT FOR SHORT TO GROUND AND OPEN CIRCUIT •  Inspect the applicable circuit for a short to ground and open circuit. (See CIRCUIT INSPECTION.) •  Is the circuit normal?	Yes	Go to the next step.
		No	Repair or replace the malfunctioning location and perform the repair completion verification.
*8	INSPECT ELECTRONICALLY CONTROLLED BRAKE UNIT GROUND CIRCUIT FOR SHORT TO POWER SUPPLY AND OPEN CIRCUIT •  Inspect the applicable circuit for a short to power supply and open circuit. (See CIRCUIT INSPECTION.) •  Is the circuit normal?	Yes	Replace the electronically controlled brake unit and perform the repair completion verification. (Open circuit in electronically controlled brake unit internal circuit) (See ELECTRONICALLY CONTROLLED BRAKE UNIT REMOVAL/INSTALLATION [L.H.D.].) (See ELECTRONICALLY CONTROLLED BRAKE UNIT REMOVAL/INSTALLATION [R.H.D.].)
		No	Repair or replace the malfunctioning location and perform the repair completion verification.
Repair completion verification	VERIFY IF MALFUNCTION CAUSE IS CORRECTED •  Install/connect the part removed/disconnected during the troubleshooting procedure. •  Has the malfunction symptom been eliminated?	Yes	Complete the symptom troubleshooting. Explain repair contents to customer.
		No	Refer to the CAN (controller area network) malfunction diagnosis flow to inspect for a CAN communication error. (See CONTROLLER AREA NETWORK (CAN) MALFUNCTION DIAGNOSIS FLOW [L.H.D. (E)].) (See CONTROLLER AREA NETWORK (CAN) MALFUNCTION DIAGNOSIS FLOW [R.H.D.].) If the CAN communication is normal, perform the diagnosis from Step 1.