Engine Controls - System/component Tests Volvo 960 I

INTRODUCTION

Before testing separate components or systems, perform procedures in BASIC TESTING article in the ENGINE PERFORMANCE Section. Since many computer-controlled and monitored components set a trouble code if they malfunction, also perform procedures in TESTS W/CODES article in the ENGINE PERFORMANCE Section.

Note. Testing individual components does not isolate shorts or opens. Unless stated otherwise in test procedure, perform all voltage tests using a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance. Use ohmmeter to isolate wiring harness shorts or opens.

Preliminary Checks

1. Warm engine to normal operating temperature. Turn off engine. If turbine shaft does not stop rotating shortly after engine stops, remove intake hose from compressor housing.
2. Verify compressor wheel rotates freely. Ensure compressor wheel does not scrape against compressor housing when wheel is pushed radially or axially.

Check & Adjust Boost Pressure

1. Connect air pressure gauge in-line between fuel limiter and intake manifold hose. Use a "T" fitting and enough hose so gauge can be carried into passenger compartment.
2. Ensure engine is at normal operating temperature. On M/T models, drive vehicle in 3rd gear at approximately 1500 RPM. On A/T models, place selector in position "2". CAUTION: To prevent damage to brakes, DO NOT apply brakes longer than 5 seconds.
3. Press accelerator pedal to floor. On A/T models, DO NOT engage kickdown. Increase engine speed to 3000 RPM, and apply brakes while keeping accelerator pedal down to obtain full load.
4. Observe boost pressure on gauge. Maximum boost pressure should be 7.0-8.0 psi (.49-.56 kg/cm 2 ). If boost pressure is incorrect, adjust boost pressure. Go to next step. CAUTION: To prevent damage to wastegate actuator, ensure wastegate actuator rod does not turn when adjusting link rod.
5. Remove seal and clip from wastegate actuator link rod. Turn link rod to adjust boost pressure to 7.5 psi (.52 kg/cm 2 ). (Scheme 9)
6. Turning link rod one turn will change boost pressure approximately.5 psi (.03 kg/cm 2 ). Turning link rod clockwise will increase boost pressure; counterclockwise will decrease boost pressure.

Scheme 9

Basic Adjustment Of Pressure Regulator Push Rod

1. Remove locking circlip from end of push rod. Connect Pressure Gauge (5230) and Pressure Tester (5496 ) to pressure regulator. (Scheme 10) Increase pressure to 7.0-7.8 psi (.49-.54 kg/cm 2 ). Press wastegate lever against turbine housing, closing wastegate valve.
2. Adjust push rod length so push rod fits exactly over wastegate valve lever. Install locking circlip, and tighten push rod lock nut. Remove pressure gauge and tester.

Scheme 10

Wastegate Valve Suction Test

Disconnect vacuum hose from pressure regulator. Attach hand vacuum pump to fitting. Increase vacuum slightly. Look through holes in flange to see if wastegate valve opens. Wastegate valve should be fully open at 6.5 in. Hg of vacuum. Replace as necessary.

COMPUTERIZED ENGINE CONTROLS

ELECTRONIC CONTROL UNIT - IGNITION (240, 740 & 940)

Note. When measuring resistance and voltage at ECU connector, DO NOT probe into front of connector. Probe only through side of connector, just enough to make a good electrical contact. Pin identification numbers are stamped on side of ECU connector.

Note. Before removing ignition control unit connector, remove fuse No. 1 (740) or fuse No. 31 (940). On 240, ensure ignition is off.

1. Turn ignition off. Disconnect ignition ECU connector. On 240, ECU is located behind panel below glove box. On 740 and 940, ECU is located behind panel on right side of accelerator pedal.
2. 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.

Power Circuit Checks

Connect a voltmeter between ignition ECU pin No. 5 (Red wire on 240 or Brown wire on 740 and 940) and ground. Voltmeter should indicate 12 volts. If voltage is not present, check wire from ignition ECU connector to in-line fuse located on left shock tower (240) or check circuit between ignition ECU pin No. 5 and fuse block (740 and 940).

Ground Circuit Checks

Turn ignition switch to OFF position. Connect ohmmeter between ignition control unit terminals No. 20 and 14, and ground. (Scheme 11) Resistance should be zero ohms.

Scheme 11

ELECTRONIC CONTROL UNIT - FUEL INJECTION (240, 740 & 940)

Note. When measuring resistance and voltage at ECU connector, DO NOT probe into front of connector. Probe only through side of connector, just enough to make a good electrical contact. Pin identification numbers are stamped on side of ECU connector.

1. Turn ignition switch to OFF position. Disconnect fuel injection ECU connector. Fuel injection ECU is located on right side of instrument panel, under kick panel. Push out clip and disconnect ECU connector.
2. Remove cover from ECU connector to expose pin identification numbers. Visually inspect all pin connector sleeves to ensure all pins are at same height.

1. Connect voltmeter leads between ECU connector pin No. 35 and ground.
2. Turn ignition switch to ON position. Voltmeter should read 12 volts. Also, crank engine and ensure battery voltage exists while engine is being cranked.

Voltage Supply For Memory Check (740, 940 & 960)

1. Information is not available from manufacturer for 240 & models with Regina fuel injection system. Connect voltmeter between fuel injection ECU terminal No. 4 and ground. Turn ignition on. Reading should be 12 volts. Connect diagnostic unit select cable to connector terminal No. 2. Connect voltmeter between fuel injection ECU terminal No. 12 and ground.
2. Reading should be 12 volts. Press button on diagnostic unit; voltage should drop to zero. If voltage reading is 12 volts when button is pressed, check diagnostic unit. If voltage is not present at fuel injection ECU, check for voltage at diagnostic unit output connector.
3. Connect voltmeter between Blue wire terminal in diagnostic unit and ground. Reading should be 12 volts. Turn ignition off. Connect ohmmeter between Black wire terminal in diagnostic unit and ground. Reading should be zero ohms. Connect ohmmeter between select cable for diagnostic unit and terminal beneath function select button.
4. Reading should be infinite. Press select button; resistance should be zero. Connect Red lead of a diode tester to terminal beneath LED. Connect Black lead to select cable. If diode tester gives reading, LED is okay. If diode tester does not give reading, install new diagnostic unit.

Ground Circuit Check

Connect ohmmeter between ground and fuel injection ECU terminals No. 5, 17, 19 and 29 (Jetronic 2.4 fuel system) or terminals No. 5, 17 and 19 (Regina fuel system). In each case, reading should be zero ohms. Wires are grounded to intake manifold.

ELECTRONIC CONTROL UNIT (960)

Note. When measuring resistance and voltage at ECU, use Measuring Unit (999 3070 ). (Scheme 12) DO NOT probe connector. Before disconnecting/connecting control unit connector, remove fuse No. 24.

Preliminary Check

Turn ignition off. Disconnect ECU connector. ECU is located behind panel on right side of accelerator pedal. Visually inspect all pin connector sleeves to ensure no pins are damaged.

Power Circuit Check

Ensure ignition is off. Connect a voltmeter between measuring unit terminals No. 18 and 19, and then between terminals No. 36 and 19. Battery voltage should be present in both cases. If not, check fuse, wiring and relay. Turn ignition on. Voltage should decrease from 12 volts to approximately .1 volt at terminal No. 36.

Turn ignition off. Connect an ohmmeter between ground and measuring unit terminals No. 19, 24, 26, 30 and 48. Ohmmeter should indicate approximately zero ohms in all cases.

ENGINE SENSORS & SWITCHES

Scheme 12

1. Turn ignition off and remove fuse No. 24. Connect Measuring Unit (999-3070 ) between ECU and ECU connector. (Scheme 12) Turn ignition on.
2. Remove fuse No. 31 to prevent engine from starting. Connect voltmeter between measuring unit terminals No. 8 and 19. Operate starter motor. Voltmeter should oscillate between.1-.5 volts. Reinstall fuse No. 31.
3. If signal is absent or faulty, turn ignition on. Using a voltmeter, probe between terminals No. 10 and 30. Voltage should be approximately 11 volts.
4. Turn ignition off. Ensure terminal No. 30 is grounded. Connect an ohmmeter between terminals No. 30 and 19. Ohmmeter should read zero ohms.

COOLANT TEMPERATURE SENSOR

1. Disconnect Coolant Temperature Sensor (CTS) connector. Connect ohmmeter leads between CTS terminals.
2. Ohmmeter should read as specified. See COOLANT TEMPERATURE SENSOR RESISTANCE table.

COOLANT TEMPERATURE SENSOR RESISTANCE

CRANKSHAFT POSITION SENSOR

1. Turn ignition off and remove fuse No. 24. Connect Measuring Unit (999-3070 p) between ECU and ECU connector. (Scheme 12)
2. Connect a millivoltmeter across measuring unit terminals No. 47 and 48. Operate starter motor. Voltmeter should read 300-400 millivolts.
3. Turn ignition off. If signal is not present or faulty, connect ohmmeter between terminals No. 47 and 48. Resistance should be 200-400 ohms, depending on pick-up temperature.
4. Connect ohmmeter between terminals No. 48 and 19, and between terminals No. 48 and 30. Resistance should be zero ohms.

MASS AIRFLOW METER (240, 740 & 940)

1. Remove rubber sleeve from airflow meter to uncover wire connector. DO NOT disconnect connector. Using a voltmeter, back probe connector terminals. Connect voltmeter leads between ground and terminal No. 5 on mass airflow connector.
2. Voltage reading should be 12 volts. Connect voltmeter leads between terminals No. 1 and 5 on mass airflow connector. Voltage reading should be 12 volts.

MASS AIRFLOW METER (960)

1. Turn ignition off and remove fuse No. 24. Connect Measuring Unit (999-3070 ) between ECU and ECU connector. (Scheme 12)
2. To ensure airflow meter is grounded, connect ohmmeter between terminals No. 19 and 26. Zero ohms should be present. Connect ohmmeter between airflow meter connector terminal No. 1 (Brown wire). Reading should be approximately zero ohms.
3. Connect ohmmeter between terminals No. 7 and 26. Reading should be approximately 2.5-4 ohms. If not to specification, measure resistance between airflow meter terminals No. 2 (Brown/White wire) and 3 (Green/Yellow wire).
4. Turn ignition on. Connect voltmeter between terminals No. 7 and 19. Approximately 1.4 volts should be present. Start engine. Voltage should increase to 2.3-2.6 volts when idling. Voltage should be 2.3 volts with engine hot.
5. If voltage reading is too low, connect voltmeter between terminals No. 25 and 19. Increase speed to 1800 RPM and stop engine. Volt-meter should read approximately 4 volts.

OXYGEN (O2) SENSOR (240, 740 & 940)

1. Warm engine to normal operating temperature. Connect exhaust gas analyzer. Disconnect O2 sensor wire (at O2 sensor) from ECU.
2. Connect a jumper wire between ECU wiring (O2 sensor harness side) and ground. CO content should increase, indicating ECU and its connections are okay.
3. Connect a voltmeter to O2 sensor. While engine is running, voltmeter should fluctuate at approximately 0.5 volts if CO constant is normal. Replace O2 sensor if not within specification.

OXYGEN (O2) SENSOR & PREHEATER RESISTOR (960)

1. Turn ignition off and remove fuse No. 24. Connect Measuring Unit (999-3070 ) between ECU and ECU connector. (Scheme 12) Turn ignition on.
2. To check oxygen sensor signal, connect voltmeter between measuring unit terminals No. 28 and 30. Voltmeter should oscillate between.1-1 volt after a short interval. If voltage remains constant at zero volts, sensor is interpreting mixture as lean. If voltage is constant at one volt, sensor is interpreting mixture as rich. Disconnect measuring unit.
3. To check voltage to oxygen sensor, start engine. Connect voltmeter between terminals No. 1 and 2 in starter motor 2-pin connector. Voltmeter should indicate battery voltage. If no voltage is present, check fuse No. 30. If voltage is present, go to next step.
4. Stop engine. To check preheater resistor, disconnect starter motor connector. Connect ohmmeter between starter motor connector terminals No. 1 and 2. Approximately 3-13 ohms should be present, depending on resistor temperature.

OXYGEN (O2) SENSOR CURRENT FEED & HEATER RESISTANCE (240, 740 & 940)

1. Connect voltmeter between ground and terminal No. 1 of 2-wire connector located next to firewall. Voltage reading should be battery voltage. Remove ground wire from fuel injection ECU terminal No. 20.
2. Connect ohmmeter between oxygen sensor harness terminal No. 2 (Black wire) and ground. Connector is located next to firewall. With a cold oxygen sensor, resistance should be 2-3 ohms. With oxygen sensor warmer than 660°F (350°C), resistance should be 7-14 ohms. Replace oxygen sensor as necessary.

THROTTLE SWITCH (240, 740 & 940)

1. Turn ignition switch to OFF position. Connect ohmmeter between fuel injection ECU terminal No. 2 and ground. With switch closed, reading should be zero ohms. Press accelerator pedal slightly. Resistance should increase to 2000-3000 ohms (switch opens).
2. Connect ohmmeter between fuel injection ECU terminal No. 3 and ground. Reading should be infinite. Press accelerator pedal to floor. Reading should be zero ohms. If a problem is found during check, perform same checks at throttle switch.
3. To check and adjust throttle switch, open throttle slightly and listen to switch. A click should be heard as soon as throttle is opened. If switch appears to be out of adjustment, loosen mount screws. Turn switch slightly clockwise, and then turn switch counterclockwise until switch clicks. Tighten mount screws, and check setting.

THROTTLE SWITCH (960)

1. Turn ignition off and remove fuse No. 24. Connect Measuring Unit (999-3070 ) between ECU and ECU connector. (Scheme 12) Turn ignition on.
2. To check throttle switch signal, connect voltmeter between terminals No. 30 and 53. Voltmeter should indicate approximately.5 volts at idle and approximately 4.5 volts at full load.
3. If signal is absent or faulty, check for a 5-volt reference signal between terminals No. 12 and 30. Voltmeter should indicate 5 volts.
4. Turn ignition off. Connect an ohmmeter between terminals No. 19 and 30. Ohmmeter should indicate approximately zero ohms. Check resistance between terminals No. 53 and 30. Resistance should be approximately 1.0 k/ohms at idle and approximately.7 k/ohms at full load.

FUEL INJECTION MAIN RELAY (240, 740 & 940)

Connect voltmeter between fuel injection ECU terminal No. 9 and ground. Connect a jumper wire between fuel injection ECU terminal No. 21 and ground. Relay should close and voltmeter should indicate battery voltage. Replace as necessary.

FUEL PUMP RELAY (240, 740 & 940)

Connect jumper wire between fuel injection ECU terminal No. 21 and ground. Connect another jumper wire between fuel injection ECU terminal No. 20 and ground. Fuel pump relay should close and fuel pump should run. Replace relay as necessary.

FUEL SYSTEM

Note. For fuel system pressure testing, see BASIC TESTING article in the ENGINE PERFORMANCE Section.

Fuel Pressure Regulator

1. Before disconnecting, cover fuel line connector with shop towel to absorb any fuel spray. Connect Fuel Pressure Gauge (5011 ) between fuel line and fuel rail. Seal free end of hose with Plug (5266 ). Start fuel pumps. On 240, remove panel under right side of instrument panel and remove system relay. (Scheme 13) On 740 and 940, lift out central electrical unit and remove system relay. (Scheme 14)
2. On 240, 740 and 940, connect a jumper wire between relay terminals No. 30 and 87/2. (Scheme 15) On 960, remove fuses No. 30 and 31. (Scheme 16) Connect a jumper wire between right fuse terminals. (Scheme 16) On all models, fuel pumps should start. Fuel filler cover can be removed to determine whether main pump is operating.
3. Fuel pressure should be 42 psi (3.0 kg/cm 2 ). If pressure is too low, pinch return hose by hand and check whether pressure rises. Do not allow pressure to exceed 86 psi (6 kg/cm 2 ). If pressure rises rapidly, replace pressure regulator.

Scheme 13

Scheme 14

Scheme 15

Scheme 16

Fuel Injectors (240, 740 Non-Turbo & 940 Non-Turbo)

1. Remove auxiliary relay, located on left front fender panel. Jumper relay terminals No. 2 and 3. Connect ohmmeter between fuel injection ECU terminals No. 9 and 18. Resistance should be 4 ohms. If resistance is 5.3 ohms, one injector or wire is faulty.
2. If resistance is 8 ohms, 2 injectors or wires are faulty. If resistance is 16 ohms, 3 injectors or wires are faulty. To check injectors individually, disconnect injector wires and place ohmmeter across suspected injector. Resistance should be 16 ohms. Replace as necessary.

Fuel Injectors (740 Turbo & 940 Turbo)

1. Remove auxiliary relay, located on left front fender panel. Jumper relay terminals No. 2 and 3. Connect ohmmeter between fuel injection ECU terminals No. 9 and 18. Resistance should be 2.25 ohms. If resistance is 2.9 ohms, one injector or wire is faulty.
2. If resistance is 4.4 ohms, 2 injectors or wires are faulty. If resistance is 8.5 ohms, 3 injectors or wires are faulty. To check injectors individually, disconnect injector wires and place ohmmeter across suspected injector. Resistance should be 2 ohms. Replace as necessary.

Fuel Injectors (960)

1. Turn ignition off and remove fuse No. 24. Connect Measuring Unit (999-3070 ) between ECU and ECU connector. (Scheme 12) Turn ignition on.
2. Connect voltmeter between measuring unit terminals No. 17 and 24, and between terminals No. 16 and 24. In both cases, battery voltage should be present.
3. Turn ignition off. Connect an ohmmeter between terminals No. 37 and 17. Resistance should be approximately 5.3 ohms. Connect ohmmeter between terminals No. 37 and 16. Resistance should be approximately 5.3 ohms.
4. Disconnect injector connectors. Using an ohmmeter, check resistance of each injector. Resistance should be 16 ohms at 68°F (20°C). Replace as necessary.

Cold Start Valve (240, 740 & 940)

1. Disconnect cold start valve harness connector. Connect ohmmeter leads across cold start valve terminals.
2. Ohmmeter should indicate 10 ohms. If reading is not 10 ohms, replace cold start valve.

IDLE CONTROL SYSTEM

Note. When measuring resistance and voltage at ECU connector, DO NOT probe into front of connector. Probe only through side of connector, just enough to make a good electrical contact. Pin identification numbers are stamped on side of ECU connector.

IDLE AIR CONTROL VALVE

1. Turn ignition switch to OFF position. Disconnect ECU connector. Remove cover from ECU connector to expose pin identification numbers. On 240, 740 and 940 with 2.4 Jetronic fuel system, connect an ohmmeter between fuel injection ECU pins No. 9 and 33.
2. Ohmmeter should read 8 ohms. On 740 and 940 with Regina fuel injection system, connect ohmmeter between fuel injection ECU pins No. 9 and 33. Ohmmeter should read 4 ohms.

IGNITION SYSTEM

Note. For basic ignition checks, see BASIC TESTING article in the ENGINE PERFORMANCE Section.

Detonation (Knock) Sensor (240, 740 & 940)

1. Disconnect knock sensor connector. Connect jumper wire across knock sensor terminals No. 1 and 2. (Scheme 17) Turn ignition off. Disconnect ignition ECU connector.
2. Remove cover from ECU connector to expose pin identification numbers. Connect ohmmeter leads between pins No. 12 and 13 of ignition ECU connector. (Scheme 11) Ohmmeter should indicate zero ohms.
3. If ohmmeter resistance is high (infinity), one or both wires may be shorted. Remove jumper wire, and take reading with ohmmeter on each wire. Replace damaged wires as required. If wires are not damaged, replace knock sensor.

Detonation (Knock) Sensors (960)

1. Turn ignition off and remove fuse No. 24. Connect Measuring Unit (999 3070) between ECU and ECU connector. (Scheme 12) Turn ignition on.
2. 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.
3. Connect an ohmmeter between measuring unit terminals No. 2 and terminal No. 11 or 29 (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).

Scheme 17

EXHAUST GAS RECIRCULATION (EGR)

1. Ensure all connections are tight and do not leak. Ensure all vacuum hoses are connected and not kinked. Check EGR function with cold and hot engine at different engine speeds.
2. With engine coolant temperature below 131°F (55°C), EGR valve should be closed at all engine speeds. If EGR valve is open, replace thermostat valve.
3. With coolant temperature above 140°F (60°C), EGR valve should only open at partial throttle. If EGR valve remains closed, check thermostat valve by disconnecting vacuum hose from EGR valve and blowing air into it. Air should flow freely through thermostatic valve. If air does not flow freely through thermostatic valve, replace valve.

FUEL EVAPORATION

Fuel evaporation testing procedures are not available from manufacturer. See VACUUM DIAGRAMS article in the ENGINE PERFORMANCE Section for information on hose routing.

MISCELLANEOUS CONTROLS

Note. Although some of the controlled devices listed here are not technically engine performance components, they can affect driveability if they malfunction.

Cooling Fan Motor (960)

1. Turn ignition off and remove fuse No. 24. Connect Measuring Unit (999 3070) between ECU and ECU connector. (Scheme 12) Turn ignition on.
2. Connect voltmeter across measuring unit terminals No. 14 and 19. Battery voltage should be present. Connect voltmeter across terminals No. 34 and 19. Battery voltage should be present.
3. If no voltage is present at control unit, check voltage supply to relay. If voltage is present, check wiring between fan motor, relay and ground.