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DTC P1242: Fail Safe Control Monitor
 
 
 
 
TECHNICAL DESCRIPTION
Monitors the engine speed during fail-safe control.
 
 
DTC SET CONDITIONS
Check Condition
  • During fail safe control.
Judgment Criterion
  • The engine speed is more than assumed.
 
 
FAIL-SAFE AND BACKUP FUNCTION
  • Throttle opening degree position is in default position.
 
 
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
  • ECM failed.
 
 
 
DIAGNOSIS
Required Special Tool:
  • MB991958: Scan Tool (M.U.T.-III Sub Assembly)
    • MB991824: V.C.I.
    • MB991827: USB Cable
    • MB991910: Main Harness A
STEP 1. Using scan tool MB991958, read the diagnostic trouble code (DTC).
cautionTo prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
(1) Connect scan tool MB991958 to the data link connector.
(2) Turn the ignition switch to the "ON" position.
(3) Read the DTC.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is the diagnostic trouble code other than P1242 set?
Refer to, Diagnostic Trouble Code Chart .
Go to Step 2.
 
STEP 2. Using scan tool MB991958, read the diagnostic trouble code (DTC).
(1) Turn the ignition switch to the "ON" position.
(2) After the DTC has been deleted, read the DTC again.
(3) Turn the ignition switch to the "LOCK" (OFF) position.
Is DTC P1242 set?
Replace the ECM (Refer to, Removal and Installation ).
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 Malfunctions .