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Electronic Control Unit For The Constant Idle Speed System

  1. Turn ignition off and remove passenger kick panel. Push latch to side and disconnect electrical connector from control unit by pulling connector down from top. Remove screw in end of connector cover and separate connector block from cover.
    NOTE: Always check terminals through holes in side of connector. Terminal numbers are stamped on side of connector.
  2. To check ground connections, connect ohmmeter between terminal "11" and ground, then terminal "25" and ground. Resistance should be zero ohms. If not, check ground points on intake manifold.
  3. To check power supply, turn ignition on. Connect voltmeter between terminal "18" and ground. Battery voltage should be registered. If not, check wire for short or open. Turn ignition off.
  4. To check system relay, connect voltmeter between terminal "9" and ground. Using a jumper wire, jumper terminal "21" to ground. Relay should energize and battery voltage should be indicated. If not, check for short or ground. If wiring is okay, replace system relay.
LH SYSTEM ELECTRICAL TEST

Component Test Terminals (1) Test Conditions Value
ECU power supply from ignition switch 18 and ground Ignition ON Battery voltage
ECU power supply from main relay 9 and ground Ignition OFF, terminal 21 grounded Battery voltage
ECU ground connections 5 and ground, 11 and ground, 19 and ground, 11 and 19, 25 and ground Ignition OFF Continuity
Fuel pump power supply from main relay N/A Ignition ON, terminal 17 grounded Fuel pumps should operate
Fuel injectors 13 (at ECU connector) and 87/2 (at main relay) Ignition OFF 4.0 ohms
Coolant temperature sensor 2 and ground Ignition OFF See COOLANT TEMPERATURE SENSOR RESISTANCE table
Throttle switch idle contacts 3 and ground Throttle closed Continuity
" " Throttle open No continuity
Throttle switch full-throttle contacts 12 and ground Throttle fully open Continuity
" " Throttle less than fully open No continuity
Air mass meter power supply 5 at air mass meter connector (orange wire) and ground Ignition ON, terminal 21 grounded Battery voltage
Air mass meter ground 1 at air mass meter connector (black wire) and ground Ignition OFF Continuity
Air mass meter hot wire 6 and 7 Ignition OFF 3.5-4.0 ohms
Air mass meter idle mixture potentiometer 6 and 14 Basic check 0-1000 ohms (varies with idle mixture adjustment)
Engine RPM signal 1 and ground Ignition ON Battery voltage
Oxygen sensor wiring harness 20 and ground Oxygen sensor connected No continuity
" " Separate connector and connect green wire to ground Continuity
Lambda-sond test connector 22 and ground Ignition OFF No continuity
Idle speed test connector 12 and ground Ignition OFF No continuity
Air control valve 10 (at ECU connector) 87/2 (at main relay) Ignition OFF Approximately 20 ohms
" 23 (at ECU connector) 87/2 (at main relay) Ignition OFF Approximately 20 ohms
AC microswitch 16 and ground AC switch OFF No continuity
" " AC switch ON Resistance varies as knob turns
(1) At ECU connector unless otherwise specified.
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