LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Volvo >> 1993 >> 850 Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Basic Testing >> Ignition Checks >> BOSCH EZ129K
April 5, 2026: LEMON Manuals is launched! Read the announcement.

BOSCH EZ129K

  1. Disconnect coil wire from distributor cap. Put coil wire next to ground and operate starter motor. If spark is present, check distributor rotor and cap. If spark is not present, go to next step.
  2. Connect voltmeter between ignition coil connector terminal No. 15 (Red wire) and ground. Turn ignition on. If battery voltage is not present, check voltage supply to ignition coil. If battery voltage is present, turn ignition off and go to next step.
  3. Connect voltmeter between ignition coil terminal No. 1 (Blue wire) and ground. Operate starter motor. If about .7-1.3 volts are present, repeat test using new ignition coil. If about .7-1.3 volts are not present, turn ignition off and go to next step.
  4. Disconnect engine speed sensor connector located close to flywheel. Connect an ohmmeter between sensor terminals. If resistance is about 200-400 ohms, go to next step and check Camshaft Position Sensor (CMP) signal. If resistance is not about 200-400 ohms, replace sensor.
    NOTE: Engine speed sensor is also known as Vehicle Speed Sensor (VSS) or impulse sensor.
  5. Remove intake hose. Bend aside rubber sleeve on CMP connector. Connect voltmeter between connector terminal No. 2 and ground. See Fig 1 . Operate starter motor. If voltage reading varies between 0-5 volts, go to step 7). If voltage reading does not vary between 0-5 volts, go to next step.
    Fig 1: Identifying Camshaft Position Sensor (CMP) Terminals
    G93F78944Courtesy of VOLVO CARS OF NORTH AMERICA.
  6. Connect voltmeter between CMP connector terminal No. 3 and ground. Turn ignition on. About 10 volts should be present. Turn ignition off. Connect an ohmmeter between CMP connector terminal No. 1 and ground. Ohmmeter should show about zero ohms. If voltage supply and ground are okay, repeat test using new CMP. If voltage supply and ground are not okay, reconnect intake hose and go to step 9).
  7. If voltage reading varied between 0-5 volts in step 5), disconnect power stage connector at ignition coil. Bend back rubber sleeve on connector. Check ground supply by connecting ohmmeter between connector terminal No. 1 and ground. See Fig 2 . Ohmmeter should indicate zero ohms. Check voltage supply by connecting voltmeter between terminal No. 3 and ground. Turn ignition on. Battery voltage should be present.
    Fig 2: Identifying Power Stage Connector Terminals
    G93H78946Courtesy of VOLVO CARS OF NORTH AMERICA.
  8. Check power stage control signal by connecting voltmeter between terminal No. 4 and ground. Operate starter motor. Voltmeter should indicate .7-1.3 volts. If ground, voltage and control signal are okay, repeat test using new power stage. If ground connection and voltage are faulty, check wiring. If control signal is not present, go to next step and check ECU input and output signals.
  9. Connect Measuring Unit (981 3190 ) and Adapter (981 3195 ) to distributor ignition ECU. See Fig 3 . Turn ignition switch to OFF position. Distributor ignition ECU is located in right side of engine compartment. Remove ECU cover. Disconnect distributor ignition ECU connector. Visually inspect all terminal connector sleeves to ensure no terminals are damaged.
    Fig 3: Connecting Measuring Unit To ECU (960 Shown; 850 Similar)
    G92I26110Courtesy of VOLVO CARS OF NORTH AMERICA.
  10. To install measuring unit, remove distributor ignition ECU. Press adapter onto distributor ignition ECU and pull lead upward through slot beside module. Press distributor ignition ECU, with adapter connected, into connector in bottom of ECU box. Connect measuring unit to adapter 60-pin connector.
  11. Ensure ignition is off. To check ECU input and output signals, connect ohmmeter between measuring unit terminal No. 20 and ground, then between measuring unit terminal No. 29 and ground. Ohmmeter should indicate about zero ohms in both cases.
  12. Ensure ignition is off. Connect ohmmeter between measuring unit terminals No. 20 and 2, and between measuring unit terminals No. 20 and 15. Ohmmeter should indicate about zero ohms in both cases.
  13. Ensure ignition is off. Connect voltmeter between measuring unit terminals No. 20 and 10. Battery voltage should be present. Turn ignition on. Connect voltmeter between measuring unit terminals No. 20 and 30. Battery voltage should be present.
  14. Check engine speed sensor signal by connecting voltmeter between measuring unit terminals No. 1 and 2. Operate starter motor. Voltmeter should indicate 300-400 millivolts. If signal is not present, check sensor. Refer to the Code 1-3-1 diagnostic procedure in the TESTS W/CODES article. If signal is present, go to next step and check Camshaft Position Sensor (CMP) signal.
    NOTE: Engine speed sensor is also known as Vehicle Speed Sensor (VSS) or impulse sensor.
  15. Connect voltmeter between measuring unit terminals No. 20 and 4. Operate starter motor. Voltage should vary between 0-5 volts. If voltage is okay, go to next step. If voltage is not okay, connect voltmeter between measuring unit terminals No. 20 and 14. Voltmeter should indicate about 10 volts. If voltage is present, but signal is not present, repeat test using new CMP. If voltage is not present, repeat test using new ECM.
  16. If voltage was okay in step 15), connect voltmeter between measuring unit terminals No. 20 and 43. Operate starter motor. Voltage should indicate about 5-7 volts. If voltage is not present, repeat test using ECU. If voltage is present, ignition system is operating properly.
scientia non olet · About LEMON Manuals