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DTC P0578: Abnormal Voltage at Cruise Control Switches
 
 
 
 
OPERATION
This circuit judges the signals of each switches (speed limiter ON/OFF, cruise control ON/OFF, CANCEL, SET - and RES +) of the cruise control switches. The PHEV-ECU detects the state of the cruise control switch by sensing the voltages shown below.
  • When all switches are released: 4.7 - 5.0 volts
  • When the cruise control ON/OFF switch is pressed: 0.9 - 1.7 volts
  • When the CANCEL switch is pressed: 1.9 - 2.7 volts
  • When the SET - switch is pressed: 2.9 - 3.6 volts
  • When the RES + switch is pressed: 3.8 - 4.5 volts
 
 
DIAGNOSTIC TROUBLE CODE SET CONDITIONS
  • If the cruise control switches is operated, this DTC will be set when the PHEV-ECU terminal voltage is different from the standard value.
  • Or, this code is set when the SET - switch or RES + switch is stuck to ON.
 
 
PROBABLE CAUSES
  • Damaged harness or connector.
  • Malfunction of the cruise control switch.
  • Malfunction of the clock spring.
  • Malfunction of the PHEV-ECU.
 
 
DIAGNOSIS
Required Special Tools:
  • MB991223: Harness Set
  • MB992006: Extra Fine Probe
STEP 1. Using scan tool (M.U.T.-IIISE), check the data list.
(1)
cautionTo prevent damage to scan tool (M.U.T.-IIISE), always turn off the power supply mode of the electric motor switch before connecting or disconnecting scan tool (M.U.T.-IIISE).
Connect scan tool (M.U.T.-IIISE). Refer to "How to connect the Scan Tool (M.U.T.-IIISE) ."
(2) Turn on the power supply mode of the electric motor switch.
(3) Using scan tool (M.U.T.-IIISE), check the PHEV-ECU data list (Refer to GROUP 54Da - data list reference table ).
  • Item No.392: CANCEL switch
  • Item No.393: RES + switch
  • Item No.394: SET - switch
  • Item No.395: Cruise control on/off switch
(4) Turn off the power supply mode of the electric motor switch.
Is the check result normal?
Go to Step 19.
Go to Step 2.
 
STEP 2. Measure the terminal voltage at cruise control switch connector.
(1) Remove the cruise control switch from the steering wheel with the cruise control switch connector connected (Refer to ).
(2) Connect the negative 12V starter battery terminal that was disconnected when the driver's air bag module was removed.
(3) Turn ON the power supply mode of the electric motor switch.
(4) Do not operate the cruise control switch.
(5) Measure the terminal voltage between cruise control switch connector terminal PHEV-ECU CRCS line and ground with cruise control switch connector connected.
OK: 4.7 - 5.0 V
Is the check result normal?
Go to Step 11.
Go to Step 3.
 
STEP 3. Measure the terminal voltage at PHEV-ECU connector by backprobing.
(1) Turn ON the power supply mode of the electric motor switch.
(2) Do not operate the cruise control switch.
(3) Measure the voltage in the CRCS wire between the PHEV-ECU connector and body ground by backprobing.
OK: 4.7 - 5.0 V
Is the check result normal?
Go to Step 8.
Go to Step 4.
 
STEP 4. Check the harness wire for short circuit to ground between PHEV-ECU connector terminal CRCS and cruise control switch connector.
(1) Check the PHEV-ECU connector.
(2) Disconnect PHEV-ECU connector and measure at the harness connector side.
(3) Turn OFF the power supply mode of the electric motor switch.
(4) Measure the continuity between PHEV-ECU connector terminal CRCS and ground.
OK: 1 kΩ or more
Is the check result normal?
Go to Step 18.
Go to Step 5.
 
STEP 5. Check of short circuit, and damage in CRCS line between PHEV-ECU connector and clock spring connector, and between clock spring connector and cruise control switch connector.
Is the check result normal?
Go to Step 6.
Repair the connector(s) or wiring harness.
 
STEP 6. Check the clock spring.
Refer to GROUP 52B - Driver's Air Bag Module and Clock Spring Inspection .
Is the check result normal?
Go to Step 7.
Replace the clock spring, and install the driver's air bag module (Refer to GROUP 52B - Driver's Air Bag Module and Clock Spring ).
 
STEP 7. Check the cruise control switches.
Refer to .
Is the check result normal?
Go to Step 10.
Replace the cruise control switches (Refer to ).
 
STEP 8. Check of open circuit, and damage in CRCS line between PHEV-ECU connector and clock spring connector, and between clock spring connector and cruise control switch connector.
Is the check result normal?
Go to Step 9.
Repair the connector(s) or wiring harness.
 
STEP 9. Check the clock spring.
Refer to GROUP 52B - Driver's Air Bag Module and Clock Spring Inspection .
Is the check result normal?
Go to Step 10.
Replace the clock spring, and install the driver's air bag module (Refer to GROUP 52B - Driver's Air Bag Module and Clock Spring ).
 
STEP 10. Using scan tool (M.U.T.-IIISE), check the PHEV system data list.
Using scan tool (M.U.T.-IIISE), check the PHEV system data list (Refer to GROUP 54Da - Data List Reference Table ).
  • Item No.392: CANCEL switch
  • Item No.393: RES + switch
  • Item No.394: SET - switch
  • Item No.395: Cruise control on/off switch
Is the check result normal?
Go to Step 19.
Go to Step 11.
 
STEP 11. Measure the terminal voltage at cruise control switch connector.
(1) Remove the cruise control switch from the steering wheel with the cruise control switch connector connected (Refer to ).
(2) Turn ON the power supply mode of the electric motor switch.
(3) Press the cruise control ON/OFF switch with cruise control switch connector connected, and measure the terminal voltage between cruise control switch connector terminal PHEV-ECU CRCG line and ground.
OK: 0.9 - 1.7 V
Is the check result normal?
Go to Step 15.
Go to Step 12.
 
STEP 12. Measure the terminal voltage at PHEV-ECU connector by backprobing.
(1) Turn ON the power supply mode of the electric motor switch.
(2) Press the cruise control ON/OFF switch, and then measure the voltage in the CRCG wire between the PHEV-ECU connector and body ground by backprobing.
OK: 0.9 - 1.7 V
Is the check result normal?
Go to Step 13.
Go to Step 18.
 
STEP 13. Check of open circuit, and damage in CRCG line between PHEV-ECU connector and clock spring connector, and between clock spring connector and cruise control switch connector.
Is the check result normal?
Go to Step 14.
Repair the connector(s) or wiring harness.
 
STEP 14. Check the clock spring.
Refer to GROUP 52B - Driver's Air Bag Module and Clock Spring Inspection .
Is the check result normal?
Go to Step 18.
Replace the clock spring, and install the driver's air bag module (Refer to GROUP 52B - Driver's Air Bag Module and Clock Spring ).
 
STEP 15. Check of short circuit, and damage in CRCG line between PHEV-ECU connector and clock spring connector, and between clock spring connector and cruise control switch connector.
Is the check result normal?
Go to Step 16.
Repair the connector(s) or wiring harness.
 
STEP 16. Check the clock spring.
Refer to GROUP 52B - Driver's Air Bag Module and Clock Spring Inspection .
Is the check result normal?
Go to Step 17.
Replace the cruise control switches (Refer to ).
 
STEP 17. Check the cruise control switches.
Refer to .
Is the check result normal?
Go to Step 18.
Replace the cruise control switches (Refer to ).
 
STEP 18. Using scan tool (M.U.T.-IIISE), check the PHEV system data list.
Using scan tool (M.U.T.-IIISE), check the PHEV-ECU data list (Refer to GROUP 54Da - Data List Reference Table ).
  • Item No.392: CANCEL switch
  • Item No.393: RES + switch
  • Item No.394: SET - switch
  • Item No.395: Cruise control on/off switch
Is the check result normal?
Go to Step 19
Replace the PHEV-ECU (Refer to GROUP 54Da - PHEV-ECU ).
 
STEP 19. Using scan tool (M.U.T.-IIISE), read the DTC.
(1) Use the scan tool (M.U.T.-IIISE), erase the DTC of the cruise control system.
(2) Turn ON the power supply mode of the electric motor switch, and press the cruise control ON/OFF switch to turn the cruise control system to ON (the cruise control display screen is turned on).
(3) After turning the cruise control system to ON, when 2 minutes or more has elapsed without operating the cruise control switches, read the DTC of the cruise control system (Refer to ).
Is DTC P0578 set?
Replace the PHEV-ECU (Refer to GROUP 54Da - PHEV-ECU ).
It can be assumed that this malfunction is intermittent (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points, How to Cope with Intermittent Malfunction ).