Page 1380 of 1500
AUTO-CRUISE CONTROL
ENGINE AND EMISSION CONTROL17-49
STEP 22. Using Diagnostic Tool MB991958, read the
diagnostic trouble codes.
To prevent damage to Diagnostic Tool MB991958, always
turn the ignition switch to the "LOCK" (OFF) position
before connecting or disconnecting Diagnostic Tool
MB991958.
(1) Connect Diagnostic Tool MB991958 to the data link
connector. (Refer to P.17-11).
(2) Turn the ignition switch to the "ON" position.
(3) Set Diagnostic Tool MB991958 to read the diagnostic
trouble codes. (Refer to P.17-11).
(4) Turn the ignition switch to the "LOCK" (OFF) position.
(5) Disconnect Diagnostic Tool MB991958.
Q: Is DTC 1571 set?
YES : Return to Step 1.
NO : The procedure is complete.
Page 1381 of 1500

AUTO-CRUISE CONTROL
ENGINE AND EMISSION CONTROL17-50
DTC 1574: Engine ECU and Its Related Components
.
DTC SET CONDITIONS
This DTC is set when there is a failure in the Engine
ECU and its related components.
.
TROUBLESHOOTING HINTS (THE MOST
LIKELY CAUSES FOR THIS CODE TO BE
SET ARE:)
Malfunction of the MPI system.
Malfunction of the A/T system.
Malfunction of the Engine ECU.
Circuit drawings
Refer to circuit diagrams GROUP-90
Refer to configuration diagrams GROUP-80
Refer to component locations GROUP-70
DIAGNOSIS
Required Special Tools:
MB991958: Diagnostic Tool (MUT-III Sub Assembly)
MB991824: V.C.I.
MB991827: MUT-III USB Cable
MB991910: MUT-III Main Harness A
STEP 1. Using Diagnostic Tool MB991958, read the MPI
system diagnostic trouble code.
To prevent damage to Diagnostic Tool MB991958, always
turn the ignition switch to the "LOCK" (OFF) position
before connecting or disconnecting Diagnostic Tool
MB991958.
(1) Connect Diagnostic Tool MB991958 to the data link
connector. (Refer to P.17-11).
(2) Turn the ignition switch to the "ON" position.
(3) Check for MPI system diagnostic trouble code. (Refer to
GROUP 13A, MPI Diagnosis
Diagnostic Function How
to Read and Erase Diagnostic Trouble Code 13A-6) .
(4) Turn the ignition switch to the "LOCK" (OFF) position.
(5) Disconnect Diagnostic Tool MB991958.
Q: Is any DTC set?
YES : Diagnose the MPI system. (Refer to GROUP 13A,
MPI Diagnosis
Diagnostic Trouble Code Chart
13A-17) . Then go to Step 4.
NO : Go to Step 2.
Page 1382 of 1500

AUTO-CRUISE CONTROL
ENGINE AND EMISSION CONTROL17-51
STEP 2. Using Diagnostic Tool MB991958, read the A/T
system diagnostic trouble code.
To prevent damage to Diagnostic Tool MB991958, always
turn the ignition switch to the "LOCK" (OFF) position
before connecting or disconnecting Diagnostic Tool
MB991958.
(1) Connect Diagnostic Tool MB991958 to the data link
connector. (Refer to P.17-11).
(2) Turn the ignition switch to the "ON" position.
(3) Check for A/T system diagnostic trouble code. (Refer to
GROUP 23A, A/T Diagnosis
Diagnostic Function How
to Read and Erase Diagnostic Trouble Code P.23A-13).
(4) Turn the ignition switch to the "LOCK" (OFF) position.
(5) Disconnect Diagnostic Tool MB991958.
Q: Is any DTC set?
YES : Diagnose the A/T system. (Refer to GROUP 23A, A/T
Diagnosis
Diagnostic Trouble Code Chart
P.23A-34). Then go to Step 4.
NO : Go to Step 3.
STEP 3. Using Diagnostic Tool MB991958, read the
auto-cruise control system diagnostic trouble code.
To prevent damage to Diagnostic Tool MB991958, always
turn the ignition switch to the "LOCK" (OFF) position
before connecting or disconnecting Diagnostic Tool
MB991958.
(1) Connect Diagnostic Tool MB991958 to the data link
connector. (Refer to P.17-11).
(2) Turn the ignition switch to the "ON" position.
(3) Use Diagnostic Tool MB991958 to read the auto-cruise
control system diagnostic trouble codes. (Refer to P.17-11).
(4) Turn the ignition switch to the "LOCK" (OFF) position.
(5) Disconnect Diagnostic Tool MB991958.
Q: Is DTC 1574 set?
YES : Replace the Engine ECU.[Refer to GROUP 13A,
Engine ECU 13A-675] . Then go to Step 4.
NO : 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 P.00-14).
Page 1383 of 1500
AUTO-CRUISE CONTROL
ENGINE AND EMISSION CONTROL17-52
STEP 4. Using Diagnostic Tool MB991958, read the
auto-cruise control system diagnostic trouble code.
To prevent damage to Diagnostic Tool MB991958, always
turn the ignition switch to the "LOCK" (OFF) position
before connecting or disconnecting Diagnostic Tool
MB991958.
(1) Connect Diagnostic Tool MB991958 to the data link
connector. (Refer to P.17-11).
(2) Turn the ignition switch to the "ON" position.
(3) Use Diagnostic Tool MB991958 to read the auto-cruise
control system diagnostic trouble codes. (Refer to P.17-11).
(4) Turn the ignition switch to the "LOCK" (OFF) position.
(5) Disconnect Diagnostic Tool MB991958.
Q: Is DTC 1574 set?
YES : Return to Step 1.
NO : The procedure is complete.
Page 1385 of 1500

AUTO-CRUISE CONTROL
ENGINE AND EMISSION CONTROL17-54
SYMPTOM PROCEDURES
INSPECTION PROCEDURE 1: When the Brake Pedal is Depressed, Auto-cruise Control System is not
Cancelled.
.
COMMENT
The stoplamp switch circuit is suspected.
.
TROUBLESHOOTING HINTS (THE MOST
LIKELY CAUSES FOR THIS CASE:)
Malfunction of the stoplamp switch.
Damaged harness or connector.
Malfunction of the Engine ECU.
Circuit drawings
Refer to circuit diagrams GROUP-90
Refer to configuration diagrams GROUP-80
Refer to component locations GROUP-70
DIAGNOSIS
Refer to P.17-35, Diagnostic Trouble Code Procedures DTC
22: Stoplamp Switch System.
INSPECTION PROCEDURE 2: When the Selector Lever is Moved to "N" Range, Auto-cruise Control
System is not Cancelled.
.
COMMENT
The transmission inhibitor switch circuit is suspected.
.
TROUBLESHOOTING HINTS (THE MOST
LIKELY CAUSES FOR THIS CASE:)
Malfunction of the transmission inhibitor switch.
Damaged harness or connector.
Malfunction of the Engine ECU.
Malfunction of A/T ECU.
Circuit drawings
Refer to circuit diagrams GROUP-90
Refer to configuration diagrams GROUP-80
Refer to component locations GROUP-70
DIAGNOSIS
Refer to GROUP 23A, A/T Diagnosis Diagnostic Trouble
Code Procedures
DTC 0705: Transmission Inhibitor Switch
System (Open/short Circuit) P.23A-97.
Page 1386 of 1500

AUTO-CRUISE CONTROL
ENGINE AND EMISSION CONTROL17-55
INSPECTION PROCEDURE 3: When the Auto-cruise Control "CANCEL" Switch is Set to ON,
Auto-cruise Control System is not Cancelled.
.
COMMENT
The cause is probably an open-circuit in the output in
the circuit inside the "CANCEL" switch.
.
TROUBLESHOOTING HINTS (THE MOST
LIKELY CAUSES FOR THIS CASE:)
Malfunction of the auto-cruise control switch.
Circuit drawings
Refer to circuit diagrams GROUP-90
Refer to configuration diagrams GROUP-80
Refer to component locations GROUP-70
DIAGNOSIS
Replace the auto-cruise control switch. (Refer to P.17-75,
Auto-cruise Control).
INSPECTION PROCEDURE 4: When the Clutch Pedal is Depressed, Auto-cruise Control System is not
Cancelled.
.
COMMENT
The clutch switch circuit is suspected.
.
TROUBLESHOOTING HINTS (THE MOST
LIKELY CAUSES FOR THIS CASE:)
Malfunction of the clutch switch.
Damaged harness or connector.
Malfunction of the Engine ECU.
Circuit drawings
Refer to circuit diagrams GROUP-90
Refer to configuration diagrams GROUP-80
Refer to component locations GROUP-70
DIAGNOSIS
Refer to P.17-15, Diagnostic Trouble Code Procedures DTC
0830: Clutch Switch System.
Page 1387 of 1500

AUTO-CRUISE CONTROL
ENGINE AND EMISSION CONTROL17-56
INSPECTION PROCEDURE 5: Auto-cruise Control System cannot be Set.
.
COMMENT
The fail-safe function is probably canceling
auto-cruise control system. In this case, Diagnostic
Tool MB991958 can be used to retest each system
by checking the diagnostic trouble codes. The
Diagnostic Tool can also be used to check if the cir-
cuits of each input switch are normal or not by check-
ing the input switch codes.
.
TROUBLESHOOTING HINTS (THE MOST
LIKELY CAUSES FOR THIS CASE:)
Malfunction of the auto-cruise control switch.
Malfunction of the stoplamp switch.
Malfunction of the transmission inhibitor switch.
Malfunction of the Engine ECU.
Circuit drawings
Refer to circuit diagrams GROUP-90
Refer to configuration diagrams GROUP-80
Refer to component locations GROUP-70
DIAGNOSIS
Required Special Tools:
MB991958: Diagnostic Tool (MUT-III Sub Assembly)
MB991824: V.C.I.
MB991827: MUT-III USB Cable
MB991910: MUT-III Main Harness A
STEP 1. Using Diagnostic Tool MB991958, read the
diagnostic trouble code.
To prevent damage to Diagnostic Tool MB991958, always
turn the ignition switch to the "LOCK" (OFF) position
before connecting or disconnecting Diagnostic Tool
MB991958.
(1) Connect Diagnostic Tool MB991958 to the data link
connector. (Refer to P.17-11).
(2) Turn the ignition switch to the "ON" position.
(3) Check for auto-cruise control system diagnostic trouble
code. (Refer to P.17-11).
(4) Turn the ignition switch to the "LOCK" (OFF) position.
(5) Disconnect Diagnostic Tool MB991958.
Q: Is DTC set?
YES : Diagnose the auto-cruise control system. (Refer to
P.17-14, Diagnostic Trouble Code Chart). Then go to
St e p 6 .
NO : Go to Step 2.
Page 1388 of 1500

AUTO-CRUISE CONTROL
ENGINE AND EMISSION CONTROL17-57
STEP 2. Using Diagnostic Tool MB991958, check data list
item 75: Cancel Switch.
To prevent damage to Diagnostic Tool MB991958, always
turn the ignition switch to the "LOCK" (OFF) position
before connecting or disconnecting Diagnostic Tool
MB991958.
(1) Connect Diagnostic Tool MB991958 to the data link
connector. (Refer to P.17-11).
(2) Turn the ignition switch to the "ON" position.
(3) Set Diagnostic ToolDiagnostic Tool MB991958 to data
reading mode for auto-cruise control system. (Refer to
P.17-11).
Item 75, Cancel Switch.
When "CANCEL" switch is at the ON position, the
display on Diagnostic Tool MB991958 should be
"ON".
When "CANCEL" switch is at the OFF position, the
display on Diagnostic Tool MB991958 should be
"OFF".
(4) Turn the ignition switch to the "LOCK" (OFF) position.
(5) Disconnect Diagnostic Tool MB991958.
Q: Is the switch operating properly?
YES : Go to Step 3.
NO : Refer to P.17-55, Symptom Procedures
Inspection
Procedure 3. Then go to Step 6.