Connect Measuring Unit (981 3190 ) and Adapter (981 3195 ) to distributor ignition ECU. Disconnect negative battery cable. Remove ECU cover located in right front engine compartment. Remove distributor ignition ECU. Press adapter onto ECU and pull lead upward through slot beside module. Press ECU, with adapter connected, into connector in bottom of ECU box. Connect measuring unit to adapter 60-pin connector.
Depending upon which knock sensor is being checked, disconnect front or rear knock sensor connector and connect a jumper wire between knock sensor connector terminals. See Fig 1 .
Connect ohmmeter between measuring unit terminals No. 22 and 23, or 24 and 25 (depending on which sensor is being checked). Reading should be zero ohms. If reading is correct, replace knock sensor. Tighten knock sensor to 15 ft. lbs. (20 N.m). If ohmmeter does not indicate zero ohms, check distributor ignition ECU wiring.

Fig 1: Knock Sensor Connector Terminals (940 Shown; 850 Similar) Id

Courtesy of VOLVO CARS OF NORTH AMERICA.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Detonation (Knock) Sensors