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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 Tools:
  • MB992744: Vehicle communication interface-Lite (V.C.I.-Lite)
  • MB992745: V.C.I.-Lite main harness A
  • MB992747: V.C.I.-Lite USB cable short
  • MB992748: V.C.I.-Lite USB cable long
  • MB991958: Scan Tool (M.U.T.-III Sub Assembly)
    • MB991824: Vehicles Communication Interface (V.C.I.)
    • MB991827: M.U.T.-III USB Cable
    • MB991910: M.U.T.-III Main Harness A (Vehicles with CAN communication system)
STEP 1. Using scan tool (M.U.T.-III), read the diagnostic trouble code (DTC).
cautionTo prevent damage to scan tool (M.U.T.-III), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-III).
(1) Connect scan tool (M.U.T.-III). Refer to HOW TO CONNECT THE SCAN TOOL (M.U.T.-III) .
(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 (M.U.T.-III), 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 .