Voltage Supply

Test voltage supply to the ECU

  • Turn the ignition on.
  • Measure the voltage between terminal 10 and system ground at terminal 17 of ECU plug.

The reading should be 11-12.5 Volts.

  • No reading: Open circuit in cable from main relay to ECU, main relay does not energize, ignition switch defective (check for voltage at terminals 86c and 88y of relay against ground). Check cable 10 connecting main relay and ECU for continuity. Check cable 17 to ground.
  • Voltage below 11 Volt: Contact resistance in cable 10 or 17 or at relay contacts.

Function of main relay section

  • Turn the ignition on.
  • Measure the voltage between relay terminals 88a, 88c and 88z with respect to ground (terminal 85).

The reading should be 11-12.5 Volt. If any of the terminals does not give system voltage the relay is defective.

Function of pump relay section

  • Turn the ignition on.
  • Measure the resistance between ECU plug terminal 20 and system ground at terminal 17.

The reading should be 52-78 Ohms. If resistance of pump relay coil is out of specification, check cable from ECU plug terminal 20 to relay terminal 86b for continuity and relay terminal 85 for continuity to ground. If these both check OK, relay is defective.

Voltage from ECU plug terminal 4 to ground at terminal 17

  • Turn the ignition on.
  • Operate the starter.
  • Measure the voltage between ECU plug terminal 4 to ground at terminal 17.

The reading should be 9-12 Volts.

  • No reading, but starter operates: Relay defective, open circuit from relay terminal 86 to ECU terminal 4, open circuit from starter terminal 50 to relay terminal 86a.
  • No reading, starter does not operate: Ignition switch defective or open circuit in cables to or from ignition switch.
  • Voltage below 9 Volt: Battery low or voltage drop in cable from ignition switch to starter terminal 50 (check cable).