DIAGNOSIS Required Special Tools: • MB991958: Scan Tool (MUT-III Sub Assembly) MB991824: V.C.I. MB991827: MUT-III USB Cable MB991911: MUT-III Main Harness B • MB991223: Harness Set

STEP 1. Check the throttle position sensor.

To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK"(OFF) position before connecting or disconnecting scan tool MB991958. (1) Using scan tool MB991958. (2) Connect scan tool MB991958 to the data link connector. (3) Turn the ignition switch to the "ON" position. (4) Read the MFI-DTC. (5) Turn the ignition switch to the "LOCK"(OFF) position. Q: Is MFI-DTC P0121, P0122 or P0123 set? YES: Refer to GROUP 13A, Diagnosis - Diagnostic Trouble Code Chart . NO: Go to Step 2 .

STEP 2. Measure the signal voltage at auto-cruise control-ECU connector C-107 by backprobing. (1) Remove the auto-cruise control-ECU mounting nut. Refer to .

(2) Do not disconnect auto-cruise control-ECU connector C-107. (3) Turn the ignition switch to the "ON" position and the auto-cruise control MAIN switch to the "ON" position.

(4) Measure the voltage between auto-cruise control-ECU connector C-107 terminal 1 and ground by backprobing. The measure voltage should measure between 4.0 and 5.5 volts. (When accelerator pedal is fully depressed.) The measure voltage should measure between 0.4 and 1.0 volts. (When accelerator pedal is released.) (5) Turn the auto-cruise control MAIN switch to the "OFF" position and the ignition switch to the "LOCK" (OFF) position. Q: Are all of the measured voltages satisfied? YES: Go to Step 5 . NO: Go to Step 3 .

STEP 3. Check auto-cruise control-ECU connector C-107, intermediate connector C-105 and throttle position sendor connector B-03 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Are the connector and terminals in good condition? YES: Go to Step 4 . NO: Repair or replace connector. Refer to GROUP 00E, Harness Connector Inspection . Then check that diagnostic trouble code 17 is not set.

STEP 4. Check the harness wire between throttle position sensor connector B-03 terminal 1 and auto-cruise control-ECU connector C-107 terminal 1 for damage.

Q: Is the harness wire in good condition? YES: Check that diagnostic trouble code 17 is not set. If diagnostic trouble code 17 is set, replace the auto-cruise control-ECU. (Refer to .) Then check that diagnostic trouble code 17 is not set. NO: Repair harness wire and then check that diagnostic trouble code 17 is not set.

STEP 5. Measure the signal voltage at ECM connector C-115.

(1) Disconnect ECM connector C-115. (2) Turn the ignition switch to the "ON" position and the auto-cruise control MAIN switch to the "ON" position.

(3) Measure the voltage between ECM connector C-115 terminal 87 and ground. The measured voltage should measure between 4.0 and 5.5 volts. (4) Turn the auto-cruise control MAIN switch to the "OFF" position and the ignition switch to the "LOCK" (OFF) position. Q: Is the measured voltage between 4.0 and 5.5 volts? YES: Check that diagnostic trouble code 17 is not set. If diagnostic trouble code 17 is set, replace the ECM. Then check that diagnostic trouble code 17 is not set. NO: Go to Step 6 .

STEP 6. Check ECM connector C-115 and auto-cruise control-ECU connector C-107 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Are the connectors and terminals in good condition? YES: Go to Step 7 . NO: Repair or replace connector. Refer to GROUP 00E, Harness Connector Inspection . Then check that diagnostic trouble code 17 is not set.

STEP 7. Check the harness wire between ECM connector C-115 terminal 87 and auto-cruise control-ECU connector C-107 terminal 2 for damage.

Q: Is the harness wire in good condition? YES: Go to Step 8 . NO: Repair harness wire and then check that diagnostic trouble code 17 is not set.