Self-Diagnostic Test (Using Voltmeter)

NOTE: Oxygen sensor memory is erased when ignition switch is turned off. To diagnose oxygen sensor, drive vehicle a good distance and keep engine running.

1. Turn ignition switch to "OFF" position. Connect voltmeter between MPI self-diagnosis output and Ground of diagnosis connector. See Fig 1 . Turn ignition switch to "ON" position and disclosure of ECU memory will begin.
   Fig 1: Self-Diagnostic Connector Location

   
2. It is important that voltage signals are accurately timed. Signals will appear in .5, 1.5 or 3 second intervals. All codes begin with voltmeter registering 12 volts for 3 seconds. If more than one code is stored in memory, codes will be separated by a 3 second voltmeter indication.
3. All codes are revealed by a 12 volt pulse, 1.5 second duration. The time between pulses is .5 second. An example of code 5 is 12 volts for 3 seconds, zero voltage for .5 second and 12 volts 1.5 seconds. The indications of zero voltage for .5 second and 12 volts 1.5 seconds will be repeated 5 times. See Fig 2 .
   Fig 2: Self-Diagnostic Code Diagram

   
4. If more than one code is stored, they will be separated by 12 volt pulses, 3 seconds in duration. After recording abnormal code, perform necessary repair as shown in SELF-DIAGNOSTIC CODE CHART. See Fig 3 . After repair, turn ignition off and disconnect negative battery cable for 15 seconds to erase ECU memory. Reconnect power supply and repeat self-diagnostics to confirm repair.

Fig 3: Self-Diagnostic Code Chart

NOTE: Perform MPI Inspection Test only after completing all steps of preceding Self-Diagnosis test.