Code No. P0642: Analog Sensor Reference Voltage No. 1 Too Low




FUNCTION



  • The engine-ECU applies 5 V to the accelerator pedal position sensor (main).
  • The engine-ECU checks whether the supply voltage is within the specified range.

TROUBLE JUDGMENT


Check Conditions
  • Battery positive voltage is 8 - 16 V
  • 2 seconds later after the ignition switch has been in "ON" position or the engine has started up
Judgment Criterion
  • The detected voltage of analogue sensor reference voltage No. 1 is 4.86 V or less. [Power supply for accelerator pedal position sensor (main)]

FAIL-SAFE AND BACKUP FUNCTION



  • The accelerator pedal opening is controlled to be 0 %.
  • The idle speed is 1,300 r/min.
  • The DPF regeneration is prohibited.
  • The EGR control is stopped (fully closed).
  • The throttle valve is opened (Electrical discontinuity).
  • The AS&G control is prohibited.

PROBABLE CAUSE



  • Failed engine-ECU

DIAGNOSIS PROCEDURE


STEP 1. M.U.T.-III diagnosis code



  • After erasing the diagnosis code through M.U.T.-III, ignition switch is "ON" position and confirm whether the diagnosis code is set.

Q. Is the diagnosis code set?

Replace the engine-ECU.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).