Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSLEXUS2012CT 200H L4-1.8L (2ZR-FXE) HYBRIDREPAIR AND DIAGNOSISA L L DIAGNOSTIC TROUBLE CODES ( DTC )TESTING AND INSPECTIONP CODE CHARTSP1578
2012 Lexus CT 200h L4-1.8L (2ZR-FXE) Hybrid
P1578
2012 Lexus CT 200h L4-1.8L (2ZR-FXE) HybridSECTION P1578
CRUISE CONTROL: CRUISE CONTROL SYSTEM: P1578: Brake System Malfunction
P1578 - Brake System Malfunction
DESCRIPTION
This DTC is output when the electronically controlled brake system has a problem. Check the electronically controlled brake system when this DTC is output.
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT
This circuit uses CAN communication. Therefore, if there are any malfunctions in the communication circuit, one or more DTCs in the CAN communication system are output.
PROCEDURE
1. CHECK DTC (ELECTRONICALLY CONTROLLED BRAKE SYSTEM)
(a) Connect the Techstream to the DLC3.
(b) Turn the power switch on (IG).
(c) Turn the Techstream on.
(d) Enter the following menus: Chassis / ABS/VSC/TRAC / Trouble Codes.
(e) Check for the DTC.
Result:
B -- GO TO ELECTRONICALLY CONTROLLED BRAKE SYSTEM How To Proceed With Troubleshooting
A -- Continue to next step.
2. CHECK WHETHER DTC OUTPUT RECORDS (CRUISE CONTROL SYSTEM)
(a) Connect the Techstream to the DLC3.
(b) Turn the power switch on (IG).
(c) Turn the Techstream on.
(d) Perform the following to make sure that the DTC detection conditions are met.
HINT
If the detection conditions are not met, the malfunction cannot be detected.
(1) Drive at a speed of between approximately 40 km/h (25 mph) and 200 km/h (125 mph).
(2) Turn the cruise control switch (ON-OFF button) on.
(3) Push the -/SET switch to activate the cruise control.
(e) Enter the following menus: Powertrain / Cruise Control / Trouble Codes.
(f) Check for DTCs.
Result:
B -- REPLACE BRAKE BOOSTER WITH MASTER CYLINDER
A -- USE SIMULATION METHOD TO CHECK How To Proceed With Troubleshooting
3. REPLACE BRAKE BOOSTER WITH MASTER CYLINDER
Replace the brake booster with master cylinder (skid control ECU) Removal.
NEXT -- Continue to next step.
4. CHECK WHETHER DTC OUTPUT RECORDS (CRUISE CONTROL SYSTEM)
(a) Connect the Techstream to the DLC3.
(b) Turn the power switch on (IG).
(c) Turn the Techstream on.
(d) Clear the DTCs Cruise Control System.
(e) Perform the following to make sure that the DTC detection conditions are met.
HINT
If the detection conditions are not met, the malfunction cannot be detected.
(1) Drive at a speed of between approximately 40 km/h (25 mph) and 200 km/h (125 mph).
(2) Turn the cruise control switch (ON-OFF button) on.
(3) Push the -/SET switch to activate the cruise control.
(f) Enter the following menus: Powertrain / Cruise Control / Trouble Codes.
(g) Check for DTCs.
Result:
B -- REPLACE POWER MANAGEMENT CONTROL ECU Removal
A -- END
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.