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Home >> Volvo >> 1991 >> 240 SE, AW70L >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Self-Diagnostics - Ignition System >> Control Function No. 2 >> Testing Impulse Sensor & Throttle Switch
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Testing Impulse Sensor & Throttle Switch

  1. Turn ignition on. Press diagnostic unit button twice, holding button for more than one second each time. Diagnostic unit light should flash rapidly. If light does not flash rapidly, turn ignition off. Disconnect ignition ECU connector.
    NOTE: Before removing ignition control unit connector, remove fuse No. 1 (740 Series) or fuse No. 31 (940 Series). On 240 Series, simply ensure ignition is off.
  2. On 240 Series, ECU is located behind panel below glove box. On 740/940 Series, ECU is located behind panel on right side of accelerator pedal. On all models, push out clip and disconnect ECU connector. Remove cover from ECU connector exposing pin identification numbers. Visually inspect all pin connector sleeves to ensure all pins are at same height.
  3. Connect a voltmeter between ignition ECU pin No. 5 and ground. Voltmeter should read 12 volts. If voltage is not present, check wire from ignition ECU connector to in-line fuse located on left shock tower (240 Series) or check circuit between ignition ECU pin No. 5 and fuse box (all others). See Fig 1.
    Fig 1: Identifying Electronic Control Unit Terminals (Ignition)
    G91H16649Courtesy of VOLVO CARS OF NORTH AMERICA.
  4. To test diagnostic unit terminals, turn ignition on. Put diagnostic unit selector cable in socket No. 6. Connect a voltmeter between ignition control unit terminal No. 1 (White wire on 240 Series or Yellow/Red wire on 740/940 Series) and ground.
  5. Voltage reading should be 12 volts. With button pressed, reading should be zero. If voltage is not present at ignition control unit, test for voltage at diagnostic unit socket No. 6. If 12 volts are present with button pressed, check test socket connector.
  6. At test socket connector, connect voltmeter between Red/Black wire terminal (240 Series) or Blue wire terminal (740/940 Series) and ground. Reading should be 12 volts. Connect ohmmeter between Brown/Black wire terminal (240 Series) or Black wire terminal (740/940 Series) and ground.
  7. Resistance should be zero ohms. Turn ignition off. Connect ohmmeter between selector cable and pin No. 8 below diagnostic unit button. Reading should be infinite. With button pressed, reading should be zero ohms.
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