Code No.P0578: Abnormal Voltage at Cruise Control Switches.
PROBABLE CAUSES
OPERATION
This circuit judges the signals of each switches (cruise
control ON/OFF, CANCEL, SET - and RES +) of the cruise
control switches. The engine-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
DIAGNOSIS CODE SET CONDITIONS
- If the cruise control switches is operated, this diagnosis code will be
stored when the engine-ECU terminal voltage is different from the standard
value.
- Or, this code is stored 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 engine-ECU.
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STEP 1. Check the data list.
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Using M.U.T.-III, check the data list (Refer to
data list reference table ).
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- Item 75: CANCEL switch
- Item 86: Cruise control ON/OFF switch
- Item 91: RES - switch
- Item 92: SET + switch
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Q.
Is the check result normal?
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Go to Step 19.
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Go to Step 2.
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STEP 2. Measure the terminal voltage at cruise control switch
connector.
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(1)Remove the cruise control switch from the steering wheel
with the cruise control switch connector connected (Refer to ).
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(2)Connect the negative battery terminal that was
disconnected when the driver’s air bag module was removed.
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(3)Turn the ignition switch to the "ON" position.
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(4)Do not operate the cruise control switch.
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(5)Measure the terminal voltage between cruise control switch
connector terminal engine-ECU CNTS line and earth with cruise control switch
connector connected. OK: 4.7 - 5.0 V
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Q.
Is the check result normal?
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Go to Step 11.
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Go to Step 3.
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STEP 3. Measure the terminal voltage at engine-ECU
connector.
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(1)Connect special tool power plant ECU check
harness (MB992110) between the engine-ECU and the body-side harness
connector. (2)Turn the ignition switch to the "ON" position. (3)Do
not operate the cruise control switch. (4)Measure the terminal voltage
between special tool 48-pin connector terminal No.107 (engine-ECU connector
terminal CNTS) and earth. OK: 4.7 - 5.0 V
Q.
Is the check result normal?
Go to Step 8.
Go to Step
4.
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STEP 4. Check the harness wire for short circuit to earth between
engine-ECU connector terminal CNTS and cruise control switch
connector.
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(1)Check the engine-ECU connector.
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(2)Disconnect engine-ECU connector and measure at the harness
connector side.
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(3)Turn the ignition switch to the "LOCK" (OFF)
position.
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(4)Measure the continuity between engine-ECU connector
terminal CNTS and earth. OK: open circuit
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Q.
Is the check result normal?
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Go to Step 18.
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Go to Step 5.
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STEP 5. Check the harness wire between engine-ECU connector terminal
CNTS and clock spring connector, and between clock spring connector
terminal and cruise control switch connector.
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- Check connector or harness wire for short circuit and damage.
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Q.
Is the check result normal?
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Go to Step 6.
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Repair connector or damaged
harness wire. Then go to Step 20.
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STEP 6. Check the clock spring.
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Refer to GROUP 52B - Driver’s Air
Bag Module and Clock Spring Inspection .
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Q.
Is the check result normal?
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Go to Step 7.
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Replace the clock spring, and
install the driver’s air bag module [Refer to GROUP 52B -
Driver’s Air Bag Module and Clock Spring ]. Then go to Step
20.
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STEP 7. Check the cruise control switches.
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Refer to .
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Q.
Is the check result normal?
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Go to Step 10.
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Replace the cruise control
switches (Refer to ). Then go to Step 20.
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STEP 8. Check the harness wire between engine-ECU connector terminal
CNTS and clock spring connector, and between clock spring connector and
cruise control switch connector.
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- Check connector or harness wire for open circuit and damage.
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Q.
Is the check result normal?
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Go to Step 9.
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Repair connector or damaged
harness wire. Then go to Step 20.
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STEP 9. Check the clock spring.
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Refer to GROUP 52B - Driver’s Air
Bag Module and Clock Spring Inspection .
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Q.
Is the check result normal?
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Go to Step 10.
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Replace the clock spring, and
install the driver’s air bag module [Refer to GROUP 52B -
Driver’s Air Bag Module and Clock Spring ]. Then go to Step
20.
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STEP 10. Check the data list.
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Using M.U.T.-III, check the data list (Refer to
data list reference table ).
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- Item 75: CANCEL switch
- Item 86: Cruise control ON/OFF switch
- Item 91: RES - switch
- Item 92: SET + switch
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Q.
Is the check result normal?
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Go to Step 19.
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Go to Step 11.
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STEP 11. Measure the terminal voltage at cruise control switch
connector.
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(1)Remove the cruise control switch from the steering wheel
with the cruise control switch connector connected (Refer to ).
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(2)Turn the ignition switch to the "ON" position.
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(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 engine-ECU SW- line and
earth. OK: 0.9 - 1.7 V
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Q.
Is the check result normal?
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Go to Step 15.
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Go to Step 12.
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STEP 12. Measure the terminal voltage at engine-ECU
connector.
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(1)Connect special tool power plant ECU check
harness (MB992110) between the engine-ECU and the body-side harness
connector. (2)Turn the ignition switch to the "ON" position. (3)Press
the cruise control ON/OFF switch, and measure the terminal voltage
between special tool 48-pin connector terminal No.95 (engine-ECU connector
terminal SW-) and earth. OK: 0.9 - 1.7
V
Q.
Is the check result normal?
Go to Step 13.
Go to Step
18.
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STEP 13. Check the harness wire between engine-ECU connector terminal
SW- and clock spring connector, and between clock spring connector
and cruise control switch connector.
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- Check connector or harness wire for open circuit and damage.
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Q.
Is the check result normal?
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Go to Step 14.
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Repair connector or damaged
harness wire. Then go to Step 20.
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STEP 14. Check the clock spring.
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Refer to GROUP 52B - Driver’s Air
Bag Module and Clock Spring Inspection .
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Q.
Is the check result normal?
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Go to Step 18.
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Replace the clock spring, and
install the driver’s air bag module [Refer to GROUP 52B -
Driver’s Air Bag Module and Clock Spring ]. Then go to Step
20.
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STEP 15. Check the harness wire between engine-ECU connector terminal
SW- and clock spring connector, and between clock spring connector
and cruise control switch connector.
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- Check connector or harness wire for short circuit and damage.
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Q.
Is the check result normal?
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Go to Step 16.
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Repair connector or damaged
harness wire. Then go to Step 20.
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STEP 16. Check the clock spring.
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Refer to GROUP 52B - Driver’s Air
Bag Module and Clock Spring Inspection .
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Q.
Is the check result normal?
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Go to Step 17.
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Replace the clock spring, and
install the driver’s air bag module [Refer to GROUP 52B -
Driver’s Air Bag Module and Clock Spring ]. Then go to Step
20.
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STEP 17. Check the cruise control switches.
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Refer to .
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Q.
Is the check result normal?
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Go to Step 18.
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Replace the cruise control
switches (Refer to ). Then go to Step 20.
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STEP 18. Check the data list.
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Using M.U.T.-III, check the data list (Refer to
data list reference table ).
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- Item 75: CANCEL switch
- Item 86: Cruise control ON/OFF switch
- Item 91: RES - switch
- Item 92: SET + switch
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Q.
Is the check result normal?
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Go to Step 19.
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Replace the engine-ECU (Refer to
GROUP 13A - Engine-ECU <4B1>, GROUP 13B
- Engine-ECU <6B3>). Then go to Step
20.
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STEP 19. Read the diagnosis code.
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(1)Use the M.U.T.-III, erase the diagnosis code of the cruise
control system.
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(2)Turn the ignition switch to the "ON" position, and press
the cruise control ON/OFF switch to turn the cruise control system to
ON (the cruise control indicator lamp <standard meter> or the
cruise control display screen <high contrast meter> is turned
on).
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(3)After turning the cruise control system to ON, when 2
minutes or more has elapsed without operating the cruise control switches,
read the diagnosis code of the cruise control system (Refer to ).
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Q.
Is diagnosis code No. P0578 stored?
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Replace the engine-ECU (Refer to
GROUP 13A - Engine-ECU <4B1>, GROUP 13B
- Engine-ECU <6B3>). Then go to Step
20.
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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 ).
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STEP 20. Check the data list.
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Using M.U.T.-III, check the data list (Refer to
data list reference table ).
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- Item 75: CANCEL switch
- Item 86: Cruise control ON/OFF switch
- Item 91: RES - switch
- Item 92: SET + switch
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Q.
Is the check result normal?
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Go to Step 21.
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Return to Step 2.
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STEP 21. Read the diagnosis code.
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(1)Use the M.U.T.-III, erase the diagnosis code of the cruise
control system.
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(2)Turn the ignition switch to the "ON" position, and press
the cruise control ON/OFF switch to turn the cruise control system to
ON (turn ON the cruise control indicator lamp).
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(3)After turning the cruise control system to ON, when 2
minutes or more has elapsed without operating the cruise control switches,
read the diagnosis code of the cruise control system (Refer to ).
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Q.
Is diagnosis code No. P0578 stored?
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Return to Step 1.
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The
procedure is complete.
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