Engine Controls - Basic Testing Volvo 960 I

INTRODUCTION

The following diagnostic steps will help prevent overlooking a simple problem. This is also where to begin diagnosis for a no-start condition.

The first step in diagnosing any driveability problem is verifying the customer complaint with a test drive under the conditions the problem reportedly occurred.

Before entering self-diagnostics, perform a careful and complete visual inspection. Most engine control problems result from mechanical breakdowns, poor electrical connections or damaged/misrouted vacuum hoses. Before condemning the computerized system, perform each test listed in this article.

Note. Perform all voltage tests using a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless otherwise instructed in test procedure.

VISUAL INSPECTION

Visually inspect all electrical wiring. Look for chafed, stretched, cut or pinched wiring. Ensure electrical connectors fit tightly and are not corroded. Ensure vacuum hoses are properly routed and not pinched or cut. See VACUUM DIAGRAMS article to verify routing and connections (if necessary). Inspect air induction system for possible vacuum leaks.

Compression

Check engine mechanical condition using a compression gauge, vacuum gauge or engine analyzer. See engine analyzer manual for specific instructions.

Exhaust System Backpressure

1. Exhaust system can be checked using a vacuum or pressure gauge. Remove O2 sensor or air injection check valve (if equipped).
2. Connect a 1-10 psi pressure gauge, and run engine at 2500 RPM. If exhaust system backpressure is greater than 1 3/4-2 psi, exhaust system or catalytic converter is plugged.
3. If using a vacuum gauge, connect vacuum gauge hose to intake manifold vacuum port and start engine. Observe vacuum gauge. Open throttle part way and hold steadily. If vacuum gauge reading slowly drops after stabilizing, exhaust system should be checked for a restriction.

FUEL SYSTEM

Fuel Pump Pressure

1. Before disconnecting, cover fuel line connector using shop towel to absorb any fuel spray. Connect Fuel Pressure Gauge (5011 ) between fuel line and fuel rail. Seal free end of hose using Plug (5266 ). Start fuel pumps. On 240, remove panel under right side of instrument panel and remove system relay. (Scheme 1) On 740 and 940, lift out central electrical unit and remove system relay. (Scheme 2)
2. On 240, 740 and 940, connect a jumper wire between relay terminals No. 30 and 87/2. (Scheme 3) On 960, remove fuses No. 30 and 31. (Scheme 4) Connect jumper wire between fuse terminalsNo. 30 and 31. 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 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 ).
4. If pressure rises rapidly, pump and lines are okay. Replace pressure regulator and recheck line pressure. If pressure rises slowly, fuel filter, fuel pump strainer or fuel lines are blocked. If pressure does not rise, fuel pump is probably faulty.
5. If pressure is too high, remove jumper wire between relay or fuse terminals. Remove return hose from pressure regulator, and blow in pipe. Remove vacuum hose from pressure regulator, and blow in pipe. If both hoses are open, pressure regulator is defective. Replace regulator, and recheck pressure.

Fuel Pump Circuit (240, 740 & 940)

1. Remove fuel injection system relay. Check voltage at terminal No. 30. (Scheme 2) If battery voltage does not exist, repair wiring between relay connector and battery.
2. Connect jumper wire between terminals No. 30 and 87/2 of fuel injection system relay connector. Fuel pump should run. If fuel pump does not run, check wiring between pump and relay. Also check wiring between terminals No. 87/1 and 85 for continuity. Repair as necessary.

Note. ECU terminal identifications are marked on unit or connector.

Fuel Pump Circuit (960)

If fuel pumps do not operate with ignition on, connect Measuring Unit (999-3070) to ECU. (Scheme 6) Connect voltmeter between terminals No. 3 and 19. Voltmeter should indicate battery voltage. If battery voltage is not present, check wiring and voltage supply to pump relay. If voltage is present, check wiring and voltage supply to fuel pump.

Injection System (Fuel Pump) Relay (240, 740 & 940)

With ECU connector removed from ECU, ground ECU connector terminals No. 17 and 21. Pump relay should activate fuel pumps and pumps should start operating. Connect voltmeter between ground and terminal 87/2 in relay. (Scheme 3) Battery voltage should be present. Disconnect ground leads from ECU terminals No. 17 and 21. Replace relay if faulty.

Scheme 1

Scheme 2

Scheme 3

Scheme 4

BENDIX REX 1

Note. ECU terminal identifications are marked on unit or connector.

Scheme 5

1. Ensure ground connections from ignition ECU and power stage to inlet manifold ground are okay. If ground connections are good, disconnect a spark plug wire from spark plug. Attach a test spark plug to disconnected spark plug wire, and ground spark plug. Crank engine, and monitor spark.
2. Strong Blue/White spark indicates engine or fuel system malfunction. If no or weak spark is present, reconnect spark plug wire to spark plug. Disconnect coil wire from distributor cap, and install test spark plug. Crank engine, and monitor spark. If no or weak spark is present, coil or ignition system primary circuit is defective.
3. If a strong Blue/White spark is present, check ignition rotor, distributor housing and spark plug wires. Replace components as necessary. If previous steps do not show defective components, go to next step.
4. Turn ignition off. Reconnect disconnected components. Ensure all connectors are secure and properly connected. With ignition off, remove panel from lower left dashboard and disconnect ignition ECU connector. Remove dust cover from connector. Ensure all pin connection sleeves are at same height.
5. Measure voltage at ignition ECU connector terminal No. 5. Voltage reading should be about 12 volts. If voltage is not present, check circuit between ignition ECU and fuse holder.
6. Turn ignition on. Open diagnostic connector at left rear of engine compartment, and connect test lead to socket No. 6 (marked on unit). (Scheme 5) Measure voltage at ignition ECU connector terminal No. 1. Voltage should be about 12 volts. Press test button on diagnostic unit. Voltage should now be zero volts. If voltage is not present at control unit or is 12 volts with button pushed, measure voltage at diagnostic unit connector.
7. Measure voltage at diagnostic unit connector Blue lead. Voltage should be about 12 volts. Using ohmmeter, check continuity between diagnostic unit connector Black lead and ground. Ensure continuity exists.
8. Turn ignition off. Check continuity between diagnostic unit test lead and pin No. 8 (under function selector button). Ohmmeter should indicate infinity. Press test button on diagnostic unit. Continuity should now be present.
9. Using ohmmeter, test for continuity of diagnostic unit LED. Connect ohmmeter leads to pin under LED and to test lead. Continuity should exist in only one direction.
10. Turn ignition on. Measure voltage at ignition ECU terminal No. 6 (Blue wire). Voltage should be about 12 volts. Turn ignition off. Using ohmmeter, check continuity between ignition ECU connector terminals No. 20 (Brown wire) and 14 (Black wire). Continuity should exist.
11. Measure resistance between ground and ignition ECU connector terminal No. 2 (Red/Black wire). See COOLANT TEMPERATURE SENSOR RESISTANCE table. If reading is not correct, test sensor directly to determine if fault is in sensor or wiring. COOLANT TEMPERATURE SENSOR RESISTANCE Temperature °F (°C) Ohms -22 (-30) 30,000 -4 (-20) 15,000-16,000 32 (0) 5800-6000 68 (20) 2200-2400 104 (40) 1000-1200 140 (60) 600 176 (80) 340-360 212 (100) 180-190 248 (120) 100-120
12. Check continuity between ignition ECU connector terminal No. 7 (Orange wire) and ground. Ensure continuity exists. Depress accelerator until throttle switch opens slightly. Ohmmeter reading should increase to infinity. If reading is not correct, measure throttle switch resistance directly to determine if fault is in switch or wiring. Adjust throttle switch if necessary. See ADJUSTMENTS article.
13. Remove panel under right side of dash, at right side of bulkhead. Remove glove compartment. Turn ignition off. Disconnect fuel injection ECU connector. Check for continuity between ignition ECU terminal No. 8 (Yellow wire) and fuel injection ECU terminal No. 25 (Yellow wire). If continuity is not present, check connectors and wiring. Repair as necessary. If continuity is still not present, internal fault is present in one of ECUs. Reconnect fuel injection ECU connector, and replace glove compartment and panel.
14. Check P/M (pulse) generator by measuring resistance between ignition ECU terminals No. 10 (Red wire) and 23 (Blue wire). Resistance should be 215-265 ohms. Ensure shield is connected to ECU terminal No. 11.
15. Disconnect knock sensor connector, and place a jumper wire between terminals. Check continuity between ignition ECU terminals No. 12 (Black wire) and 13 (Green wire). Ohmmeter should show continuity. Ensure resistance to ground is infinity. If resistance is too high (infinity), remove jumper wire and test each wiring lead. If leads are intact, replace knock sensor.
16. Reconnect knock sensor connector. Reassemble and reconnect ignition ECU connector.
17. Disconnect connectors from ignition coil and power stage. Remove mounting screws and lift ignition coil from power stage. Measure resistance across low tension side of ignition coil. Resistance should be about.5 ohm.
18. Measure resistance between high tension terminal and each low tension terminal. Resistance should be about 5000 ohms. If resistance is not as specified, replace ignition coil.
19. Turn ignition on. Check for battery voltage at Blue wire of 3-pin power stage connector. If voltage is low or does not exist, check power supply lead connections at ignition ECU and ignition coil/power stage. Ensure voltage does not drop to less than 10.5 volts while engine is cranking. Turn ignition off.
20. Ensure ground is present at Brown/Black wire of 3-pin power stage connector and at Black wire of 2-pin power stage connector. Using a self-powered test light or buzzer, check for continuity between Orange wire of 2-pin power stage connector and ignition ECU terminal No. 16.
21. If no defects are found in previous steps or engine still malfunctions after repairs, install new ignition ECU. Recheck system as necessary. Reinstall ignition coil. Reassemble ignition ECU connector, and reconnect it to ECU. Reconnect ignition coil/power stage connectors.

BOSCH EZ116K

Note. ECU terminal identifications are marked on unit or connector.

240, 740 & 940

1. Ensure ground connections from ignition ECU and power stage to inlet manifold ground are okay. If ground connections are good, disconnect a spark plug wire from spark plug. Connect a test spark plug to disconnected spark plug wire, and ground spark plug. Crank engine, and monitor spark.
2. A strong Blue/White spark indicates engine or fuel system malfunction. If no or weak spark is present, reconnect spark plug wire to spark plug. Disconnect coil wire from distributor cap, and install test spark plug. Crank engine, and monitor spark. If no spark or weak spark is present, coil or ignition system primary circuit is defective.
3. If a strong Blue/White spark is present, check ignition rotor, distributor housing and spark plug wires. Replace components as necessary. If previous steps show no defective components, go to next step.
4. Turn ignition off. Reconnect disconnected components. Ensure all connectors are secure and properly connected. With ignition off, remove panel from lower left dashboard and disconnect ignition ECU connector. Remove dust cover from connector. Ensure all ECU pin connection sleeves are at same height.
5. Measure voltage at ignition ECU connector terminal No. 5. Voltage should be about 12 volts. If voltage is not present, check circuit between ignition ECU and fuse holder.
6. Turn ignition on. Open diagnostic connector at left rear of engine compartment, and connect test lead to socket No. 6 (marked on unit). (Scheme 5) Measure voltage at ignition ECU connector terminal No. 1. Voltage should be about 12 volts. Press test button on diagnostic unit. Voltage should now be zero volt. If voltage is not present at control unit or if voltmeter reads 12 volts with button pushed, measure voltage at diagnostic unit connector.
7. Measure voltage at diagnostic unit connector Blue lead. Voltage should be about 12 volts. Using ohmmeter, check continuity between diagnostic connector Black lead and ground. Continuity should exist.
8. Turn ignition off. Check continuity between diagnostic test lead and pin No. 8 (under function selector button). Ohmmeter should read infinity. Press button on diagnostic unit. Ohmmeter should now show continuity.
9. Using ohmmeter, check continuity of diagnostic unit LED. Connect ohmmeter leads to test lead and to pin under LED. Continuity should exist in one direction only.
10. Turn ignition on. Measure voltage at ignition ECU terminal No. 6 (Blue wire). Voltage should be about 12 volts. Turn ignition off. Check continuity between ignition ECU connector terminals No. 20 (Brown wire) and 14 (Black wire). Continuity should be present.
11. Measure resistance between ground and ignition ECU connector terminal No. 2 (Red/Black wire). See COOLANT TEMPERATURE SENSOR RESISTANCE table under BENDIX REX 1. If reading is not correct, test sensor directly to determine if fault is in sensor or wiring.
12. Check continuity between ignition ECU connector terminal No. 7 (Orange wire) and ground. Ohmmeter should show continuity. Depress accelerator until throttle switch opens slightly. Ohmmeter reading should increase to infinity. If reading is not correct, measure throttle switch resistance directly to determine if fault is in switch or wiring. Adjust throttle switch if necessary. See ADJUSTMENTS article.
13. Measure voltage at ignition ECU connector terminal No. 8 (Yellow wire). Turn ignition on. Voltage should be about.1 volt. If reading is not correct, check for open circuit between ignition ECU and fuel injection ECU or for fault in fuel injection ECU.
14. Turn ignition off. Measure resistance between ignition ECU connector terminals No. 10 (Red wire) and 23 (Blue wire). Resistance should be 215-265 ohms. Ensure shield is connected to ignition ECU terminal No. 11.
15. Disconnect knock sensor connector and place a jumper wire between terminals. Check continuity between ignition ECU terminals No. 12 (Black wire) and 13 (Green wire). Ohmmeter should show continuity. Ensure resistance to ground is infinity. If resistance is too high (infinity), remove jumper wire and test each wiring lead. If leads are intact, replace knock sensor.
16. Reconnect knock sensor connector. Reassemble and reconnect ignition ECU connector.
17. Remove air cleaner assembly. Ensure ignition is off, and disconnect power stage connector. Power stage is located at front of left front fender panel. Remove connector dust cover. Connect multimeter negative (-) lead to ground and positive (+) lead to connector pin No. 4. Turn ignition on, and note voltage reading. Voltage should be about 12 volts.
18. Leave multimeter attached, and crank starter motor. Voltage should be at least 10.5 volts. If voltage is too low, check battery and charging system. If voltage is not present, check Blue wire from ignition ECU to ignition coil and power stage. Repair or replace as necessary.
19. Check continuity of power stage ground by connecting multimeter to power stage connector pin No. 2 and ground. Multimeter should show continuity. Check ignition coil resistance. Connect multimeter to power stage connector pins No. 1 and 4. Resistance should be 0.6-1.0 ohm. If resistance is less than 0.6 ohm, check wires for short circuit.
20. If wires are okay but resistance is still not 0.6-1.0 ohm, connect multimeter between ignition coil terminals No. 1 (Red/White wire) and No. 15 (Blue wire). If resistance is not 0.6-1.0 ohm, install a new ignition coil. If resistance is 0.6-1.0 ohm, check continuity of wires between ignition coil and power stage connector pins No. 1 and 4. Repair or replace as necessary.
21. Check shield (ground) wire between ignition ECU and power stage. Shield wire is connected to power stage connector pin No. 3 (Gray wire). Repair if necessary. Ensure power stage is receiving signal from ignition ECU. Disconnect wires from ignition coil terminalNo. 1. Connect multimeter positive (+) lead to power stage connector pin No. 5 and negative (-) lead to ground.
22. Crank starter motor, and monitor voltage reading. Voltage should pulsate between 0 and 2 volts. If voltage is within specification, install a new power stage and recheck circuit. If voltage is very low and/or irregular, check wiring between ignition ECU and crankshaft position sensor. Repair or replace as necessary.
23. Turn ignition off. If no defects are found in previous steps or if engine still malfunctions after repairs, install a new ignition ECU. Recheck system as necessary.

960 (Determining Whether Fault Is Fuel Or Ignition)

Using a volt-meter, check voltage at injectors when engine is hot. If voltage is about 250-400 millivolts, fault is in ignition system and/or an injector is blocked.

Checking Ground Connections

1. Turn ignition off. Remove fuse No. 24. Connect Measuring Unit (999-3070 ) to ECU. (Scheme 6) Connect ohmmeter between ground and terminals No. 19, 24, 26, 30 and 48. Resistance should be about zero ohms on all measurements.
2. Check power unit ground connections under each power unit. Connect an ohmmeter between ground and terminal No. 4 on front power unit connector and then on rear power unit connector.
3. Ohmmeter should indicate about zero ohms in both cases. If ohmmeter does not indicate about zero ohms in both cases, check connectors and wiring.

Scheme 6

Voltage Supply To Ignition Coils

Turn ignition on. Connect volt-meter between ground and test terminal at rear of engine. (Scheme 7) Voltmeter should show battery voltage. If battery voltage is not present, check relay, wiring and connectors.

Scheme 7

Cylinder Miss

Idle engine. Disconnect and reconnect one injector connector at a time. If engine speed drops when connector is disconnected, cylinder is okay.

Scheme 8

1. Make an adapter to fit between ignition coil connector and test diode (999-5280 ). Connect test diode. (Scheme 8)
2. Start engine. Diode should flash if signal is present. If signal is present, go to step 5). If no signal is present, connect voltmeter between ground and control unit terminals connected to each ignition coil.
3. If voltage is about 3.5 volts, an open circuit is present between control unit and ignition coil. If voltmeter indicates 60-100 millivolts, connect diode tester with positive side connected to control unit terminal for cylinder to be checked and to terminal No. 1 on corresponding ignition coil connector. Check components with leads reversed.
4. Connect diode tester with positive side connected to ground and to terminal No. 1 on ignition coil connector. Check components with leads reversed. If fault is present, check wiring.
5. Remove coil and plug. Install another plug in cylinder. Install original plug in ignition coil. Start engine and check for spark. If no spark is present, check whether coil or plug is faulty. Install plug in another coil. If spark is present, replace original coil. If no spark is present, replace spark plug.

IDLE SPEED & IGNITION TIMING

Ensure idle speed and ignition timing are set to specification. For idle speed adjustment procedures, see ADJUSTMENTS article. Ignition timing is not adjustable.

IDLE SPEED & CO LEVEL

IGNITION TIMING (Degrees BTDC @ RPM)

SUMMARY

If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, proceed to appropriate SELF-DIAGNOSTICS article. If no hard codes are found in self-diagnostics, proceed to TESTS W/O CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.