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Cruise Control System (Diagnostic Codes & Circuit Tests): Overview Lexus CT I

Cruise Control Systems 12 illustrations ~1587 words

DESCRIPTION

When the brake pedal is depressed, the stop light switch assembly sends a signal to the power management control ECU. When the power management control ECU receives this signal, it cancels the cruise control. The fail-safe function operates to enable normal driving even if there is a malfunction in the stop light signal circuit. Cruise control cancellation occurs when voltage is applied to terminal STP. When the brake is applied, voltage is normally applied to terminal STP of the power management control ECU through the STOP fuse and the stop light switch assembly, and the power management control ECU turns the cruise control off.

DTC No.DTC Detection ConditionTrouble Area
P0571Voltage of STP signal and that of ST1- signal of power management control ECU are less than 1 V for 0.5 seconds or moreStop light switch assembly Stop light switch assembly circuit Power management control ECU

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Scheme 43: WIRING DIAGRAM
Scheme 43: WIRING DIAGRAM

This DTC indicates the internal abnormalities of the power management control ECU.

DTC No.DTC Detection ConditionTrouble Area
P0575When both of the following conditions are met: STP signals input to the power management control ECU supervisory CPU and control ECU are different for 0.15 seconds or more 0.4 seconds have passed after cruise cancel input signal (STP input) is input to the power management control ECUPower management control ECU

HINT

The power management control ECU receives signals from each sensor to control all functions of the cruise control system. When a trouble code is detected, the fail-safe function activates and remains on until the power switch is turned off.

This DTC is output when the electronically controlled brake system has a problem. Check the electronically controlled brake system when this DTC is output.

DTC No.DTC Detection ConditionTrouble Area
P1578The power management control ECU receives a brake system error signal for 0.2 sec. or more while the cruise control is in operationElectronically controlled brake system Power management control ECU

Scheme 44

Scheme 44: WIRING DIAGRAM
Scheme 44: WIRING DIAGRAM

The vehicle speed sensors send vehicle speed signals to the brake booster with master cylinder (skid control ECU). Signals are then sent to the power management control ECU.

DTC No.DTC Detection ConditionTrouble Area
U0122While power switch is on (IG), communication stop between brake booster with master cylinder (skid control ECU) and power management control ECU continues for 2.6 seconds or moreBrake booster with master cylinder (skid control ECU) CAN communication system Power management control ECU

The cruise control switch operates 7 functions: SET, - (COAST), TAP-DOWN, RES (RESUME), + (ACCEL), TAP-UP, and CANCEL. The SET, TAP-DOWN, and - functions, and the RES, TAP-UP, and + functions are operated with the same switch. The cruise control switch is an automatic return type switch which turns on only while it is being operated it in the direction of each arrow and turns off after being released. The internal contact point of the cruise control switch is turned on with the switch operation. Then the power management control ECU reads the voltage value that has been changed by the switch operation to control the SET, -, RES, +, and CANCEL functions.

Scheme 45

Scheme 45: WIRING DIAGRAM
Scheme 45: WIRING DIAGRAM

Scheme 46

Scheme 46: PROCEDURE
Scheme 46: PROCEDURE

Scheme 47

Scheme 47
Scheme 47

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Scheme 49
Scheme 49

Scheme 50

Scheme 50
Scheme 50
  1. READ VALUE USING TECHSTREAM Connect the Techstream to the DLC3. Turn the power switch on (IG). Turn the Techstream on. Enter the following menus: Powertrain / Cruise Control / Data List. Check the Data List to confirm proper function of the cruise control switch. CRUISE CONTROL Techstream Display Measurement Item/Range Normal Condition Diagnostic Note Main SW M-CPU Cruise control switch (Main CPU) / ON or OFF ON: Cruise control switch on OFF: Cruise control switch off - Cancel Switch CANCEL switch signal / ON or OFF ON: CANCEL switch on OFF: CANCEL switch off - SET/COAST Switch -/SET switch signal / ON or OFF ON: -/SET switch on OFF: -/SET switch off - RES/ACC Switch +/RES switch signal / ON or OFF ON: +/RES switch on OFF: +/RES switch off - Main SW S-CPU Cruise control switch (S-CPU) / ON or OFF ON: Cruise control switch on OFF: Cruise control switch off - TEXT IN ILLUSTRATION *a ON/OFF *b -/SET *c +/RES *d CANCEL OK When the cruise control switch is operated, the display changes as shown above. NG --> See step 2 OK --> See step 7
  2. INSPECT CRUISE CONTROL SWITCH Remove the cruise control switch. Refer to «REMOVAL»(/lexus/ct/i-2010-2014/remont/cruise-control-systems/#cruise-control-system-service-information) . Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Switch Condition Specified Condition 1 - 3 Cruise control switch off 1 Mohms or higher Cruise control switch on Below 2.5 ohms +/RES 235 to 245 ohms -/SET 617 to 643 ohms CANCEL 1509 to 1571 ohms TEXT IN ILLUSTRATION *1 Cruise Control Switch (ON-OFF button) - - *a Component without harness connected (Cruise Control Switch) *b ON-OFF *c +/RES *d -/SET e CANCEL - - Reinstall the cruise control switch. Refer to «INSTALLATION»(/lexus/ct/i-2010-2014/remont/cruise-control-systems/#cruise-control-system-service-information) . NG --> See step 8 OK: Go to next step
  3. CHECK HARNESS AND CONNECTOR (CRUISE CONTROL SWITCH - SPIRAL CABLE SUB-ASSEMBLY) Disconnect the spiral with sensor cable sub-assembly connector. Disconnect the cruise control switch connector. Measure the resistance according to the value(s) in the table below. Standard Resistance (Check for Open) Tester Connection Condition Specified Condition Cruise control switch side connector terminal 3 - z5-3 Always Below 1 ohms Cruise control switch side connector terminal 1 - z5-4 Always Below 1 ohms TEXT IN ILLUSTRATION *a Front view of wire harness connector (to Spiral with Sensor Cable Sub-assembly) *b Front view of wire harness connector (to Cruise Control Switch) Reconnect the cruise control switch connector. Reconnect the spiral with sensor cable sub-assembly connector. NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR (CRUISE CONTROL SWITCH - SPIRAL CABLE SUB-ASSEMBLY) OK: Go to next step
  4. CHECK SPIRAL WITH SENSOR CABLE SUB-ASSEMBLY NOTE: The spiral with sensor cable sub-assembly is an important part of the SRS airbag system. Incorrect removal or installation of the spiral with sensor cable sub-assembly may cause airbag deployment. Be sure to read information shown in the link/brackets. Remove the spiral with sensor cable sub-assembly. Refer to «REMOVAL»(ref-568591-S41235317052013072300000) . Measure the resistance according to the value(s) in the table below. Standard Resistance (Check for Open) Tester Connection Condition Specified Condition z5-3 - H30-1 (CCS) The spiral with sensor cable sub-assembly is centered Below 1 ohms The spiral with sensor cable sub-assembly position is 2.5 rotations to the left The spiral with sensor cable sub-assembly position is 2.5 rotations to the right z5-4 - H30-2 (ECC) The spiral with sensor cable sub-assembly is centered Below 1 ohms The spiral with sensor cable sub-assembly position is 2.5 rotations to the left The spiral with sensor cable sub-assembly position is 2.5 rotations to the right TEXT IN ILLUSTRATION *a Component without harness connected (Spiral with Sensor Cable Sub-assembly) HINT: The spiral with sensor cable sub-assembly makes a maximum of approximately 5 rotations. Reinstall the spiral with sensor cable sub-assembly. Refer to «INSTALLATION»(ref-568591-S28659459372013072300000) . NG --> See step 9 OK: Go to next step
  5. CHECK HARNESS AND CONNECTOR (SPIRAL CABLE SUB-ASSEMBLY - POWER MANAGEMENT CONTROL ECU) Disconnect the power management control ECU connector. Disconnect the spiral with sensor cable sub-assembly connector. Measure the resistance according to the value(s) in the table below. Standard Resistance (Check for Open) Tester Connection Condition Specified Condition H30-1 (CCS) - H4-22 (CCS) Always Below 1 ohms Standard Resistance (Check for Short) Tester Connection Condition Specified Condition H30-1 (CCS) or H4-22 (CCS) - Body ground Always 10 kohms or higher Reconnect the spiral with sensor cable sub-assembly connector. Reconnect the power management control ECU connector. NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR (SPIRAL CABLE SUB-ASSEMBLY - POWER MANAGEMENT CONTROL ECU) OK: Go to next step
  6. CHECK HARNESS AND CONNECTOR (SPIRAL WITH SENSOR CABLE SUB-ASSEMBLY - BODY GROUND) Disconnect the spiral with sensor cable sub-assembly connector. Measure the resistance according to the value(s) in the table below. Standard Resistance (Check for Open) Tester Connection Condition Specified Condition H30-2 (ECC) - Body ground Always Below 1 ohms TEXT IN ILLUSTRATION *a Front view of wire harness connector (to Spiral with Sensor Cable Sub-assembly) Reconnect the spiral with sensor cable sub-assembly connector. NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR (SPIRAL WITH SENSOR CABLE SUB-ASSEMBLY - BODY GROUND) OK --> See step 10
  7. PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE. Refer to «PROBLEM SYMPTOMS TABLE»(ref-568774-S15830318722013072300000)
  8. REPLACE CRUISE CONTROL SWITCH. Refer to «REMOVAL»(/lexus/ct/i-2010-2014/remont/cruise-control-systems/#cruise-control-system-service-information)
  9. REPLACE SPIRAL WITH SENSOR CABLE SUB-ASSEMBLY. Refer to «REMOVAL»(ref-568591-S41235317052013072300000)
  10. REPLACE POWER MANAGEMENT CONTROL ECU. Refer to «REMOVAL»(/lexus/ct/i-2010-2014/remont/body-electrical/#power-distribution-service-information)
  1. The power management control ECU detects a cruise control switch signal and sends it to the combination meter assembly through CAN. Then the cruise control indicator light comes on.
  2. The cruise control indicator light circuit uses CAN for communication. If there is a malfunction in this circuit, check for DTCs in the CAN communication system before troubleshooting this circuit.

Scheme 51

Scheme 51: WIRING DIAGRAM
Scheme 51: WIRING DIAGRAM

Connecting terminals TC and CG of the DLC3 causes the system to enter self-diagnostic mode. If a malfunction is present, the cruise control indicator light will blink.

HINT

When a particular warning light remains blinking, a ground short in the wiring of terminal TC of the DLC3 or an internal ground short in the relevant ECU is suspected.

Scheme 52

Scheme 52: WIRING DIAGRAM
Scheme 52: WIRING DIAGRAM

Scheme 53

Scheme 53: PROCEDURE
Scheme 53: PROCEDURE

Scheme 54

Scheme 54
Scheme 54
  1. CHECK HARNESS AND CONNECTOR (TERMINAL TC of DLC3 - POWER MANAGEMENT CONTROL ECU) Disconnect the power management control ECU connector. Measure the resistance according to the value(s) in the table below. Standard Resistance (Check for Open) Tester Connection Condition Specified Condition H3-11 (TC) - H44-13 (TC) Always Below 1 ohms Reconnect the power management control ECU connector. NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR (DLC3 - POWER MANAGEMENT CONTROL ECU) OK: Go to next step
  2. CHECK HARNESS AND CONNECTOR (TERMINAL CG of DLC3 - BODY GROUND) Measure the resistance according to the value(s) in the table below. Standard Resistance (Check for Open) Tester Connection Condition Specified Condition H44-4 (CG) - Body ground Always Below 1 ohms TEXT IN ILLUSTRATION *a DLC3 NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR (DLC3 - BODY GROUND) OK: Go to next step
  3. CHECK HARNESS AND CONNECTOR (TERMINAL TC of DLC3 - BODY GROUND) Measure the resistance according to the value(s) in the table below. Standard Resistance (Check for Short) Tester Connection Condition Specified Condition H44-13 (TC) - Body ground Always 10 kohms or higher TEXT IN ILLUSTRATION *a DLC3 NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OR EACH ECU OK --> See step 4
  4. PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE. Refer to «PROBLEM SYMPTOMS TABLE»(ref-568774-S15830318722013072300000)

See also:
• REMOVAL
• REMOVAL

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