Ignition System - Bosch Ezk (4-cyl) Volvo 760 I

DESCRIPTION

There are 3 types of the EZK systems. The systems are similar in components and operations. The Volvo 740 and 760 with B230F/FT engines use an EZ117K type.

The EZK system consists of a breakerless Hall Effect distributor, an ignition Electronic Control Unit (ECU), a knock sensor, an LED knock indicator, an amplifier module, ignition coil and a potentiometer and microswitch mounted on the throttle housing.

OPERATION

Inputs from engine speed, engine load, detonation, throttle position and battery voltage are supplied to the micro-processor within the ignition module to determine spark advance. Only the engine load and engine speed input signal values are used to determine the timing signal entered in the memory of the micro-processor. The microprocessor, after analyzing the parameters of engine operation, will adjust timing accordingly.

The ECU output signals provide control for the amplifier module, whose final transistor will make or break the primary coil circuit. The output signals also control the full load enrichening circuit of the injection ECU and the LED knock indicator.

PRELIMINARY TEST PROCEDURES

Ignition Secondary Checks and Coil Resistance Checks are basic system tests, required whenever ignition problems are suspected. See the TROUBLE SHOOTING - BASIC PROCEDURES article in the GENERAL TROUBLE SHOOTING section. Also check for hard codes which may be set in the computer. If any codes are set they must be checked and/or corrected prior to the following testing procedures.

Power Stage Location & Connector Identification. Scheme 1

Ignition Coil Terminal Identification. Scheme 2

Sectional View of Hall Effect Distributor. Scheme 3

FAULT TRACING WITH LED TESTER (B230F/FT WITH EZ117K SYSTEM)

1. Install LED Tester using manufacturer's instructions. Turn ignition on. Diode light should be on. If light does not come on, check for an open circuit between test point connector wire and ignition ECU connector pin No. 3. (Scheme 4) Repair and repeat test as necessary.
2. If light did come on, start engine and slowly increase the RPM. The light should go out when engine RPM is greater than 920 RPM. If light does not go out, there is a defect in the ignition ECU or a short circuit in the test point wiring. Repair and repeat testing.
3. With step 1) and 2) completed, a test drive of the vehicle is necessary. Using a helper to monitor the LED Tester, the LED Tester will flash according to the fault signal it receives from the ECU. Proceed to the next step.
4. Drive vehicle under full load acceleration. If one flash is counted, pre-ignition is indicated. Check for low fuel octane, high ignition setting, defective spark plugs or improper torque, low fuel pressure or restricted injectors. In hot climates or high altitudes, maximum retard may be encountered. There is no need for concern if engine knock does not occur.
5. Operate engine at 3500 RPM for 5 seconds and allow it to run at idle. If 4 flashes are counted, a safety retard will be activated at high load and there will be a loss of power. Check knock sensor connector and torque. Check for open between knock sensor and ignition ECU. Ensure wires from knock sensor to ignition ECU are not reversed. Check for defective ignition ECU.
6. Operate engine with open throttle switch. If 5 flashes are counted, a defective load signal will cause low ignition advance and loss of power. Check for open circuit between ignition ECU connector pin No. 8 and fuel ECU connector pin No. 24. Check for defective fuel ECU and/or ignition ECU. Proceed to CIRCUIT CHECKS in this article.

EZ117K Connector & Pin Identification. Scheme 4

Scheme 5

Scheme 6

Scheme 7

1. Check for voltage at ignition coil with a multimeter. Attach multimeter negative (-) lead to ground and positive (+) lead to coil terminal No. 15. (Scheme 2) Turn ignition on and note voltage. Voltage should be approximately 12 volts. If no voltage is present, check for broken wire between coil and ignition ECU.
2. Turn ignition off. Disconnect power stage connector and remove dust cover. Connect multimeter negative (-) lead to ground. Turn ignition on. Touch multimeter positive (+) lead to connector pin No. 1 and note voltage reading. Touch positive (+) lead to connector pin No. 4 and note voltage reading. Voltage should be approximately 12 volts.
3. If no voltage is present, check for a broken wire between power stage connector and ignition ECU. Turn ignition off. Check ignition coil resistance. Resistance measurement should be taken at an ambient temperature of 68°F (20°C). Attach multimeter lead between power stage connector pins No. 1 and 4. Resistance should be 0.6-0.9 ohm.
4. If resistance is not within specifications, check resistance at ignition coil. Attach multimeter leads between ignition coil terminals No. 1 and 15. (Scheme 2) Resistance should be 0.6-0.9 ohm. If not within specifications, replace coil assembly and recheck.
5. If resistance is within specifications, check continuity of wires between ignition coil and power stage connector pins No. 1 and 4. Repair or replace as necessary.
6. Turn ignition off and disconnect ignition coil leads. Check ignition coil secondary windings resistance. Attach multimeter leads between ignition coil tower and terminal No. 1 of the coil. (Scheme 2) Resistance should be 6500-9000 ohms. If not within specifications, install a new ignition coil and recheck.
7. Check power stage ground resistance. Turn ignition off. Attach multimeter positive (+) lead to power stage connector pin No. 2 and negative (-) lead to ground. Resistance should be zero ohm. If resistance is other than zero ohm, check continuity of wire between connector pin No. 2 and intake manifold. Repair or replace as necessary.
8. Check shield (ground) wire between ignition ECU connector pin No. 16 and power stage connector pin No. 5. Shield wire should be connected to power stage connector pin No. 3. (Scheme 1) (Scheme 5): Distributor Connection Identification
9. Check voltage signal from ignition ECU to power stage with multimeter. Disconnect Red/White wire from ignition coil terminal No. 1 and Blue wire from coil terminal No. 15. (Scheme 2) Attach multimeter positive (+) lead to power stage connector pin No. 5 and negative (-) lead to ground. Crank starter motor and monitor voltage reading. Voltage should be approximately 2 volts. If no voltage is present, proceed to step 18).
10. Turn ignition off and reconnect ignition coil wires. Reconnect power stage connector. Disconnect distributor electrical connector. Attach multimeter negative (-) lead to ground. Turn ignition on. Touch multimeter positive (+) lead to harness connector pin No. 3. (Scheme 5) Voltage should be approximately 11 volts. If no voltage is present, proceed to step 16).
11. Leave multimeter negative (-) lead attached to ground and attach positive (+) lead to harness connector pin No. 2. Turn ignition on and note voltage reading. Voltage should be approximately 5 volts. If no voltage is present, proceed to step 18). If other than 5 volts are present, replace ignition ECU and recheck.
12. Turn ignition off and check distributor ground resistance. Leave multimeter negative (-) lead attached to ground and attach positive (+) lead to harness connector pin No. 1. Resistance should be zero ohm. If infinite resistance is present, check for poor or no ground connection at ignition ECU connector pin No. 20. Replace defective ignition ECU and perform step 18).
13. Turn ignition off and reconnect distributor electrical connector. Remove panel under steering wheel. Remove ignition ECU from above pedal cluster. Disconnect ECU connector and remove dust cover and side covers. Carefully reconnect connector to ECU. Ensure ignition is off.
14. Disconnect ignition coil Red-White wire and Blue wire. Attach multimeter negative (-) lead to ground and positive (+) lead to ECU connector pin No. 24 at rear of connector. Turn ignition on. Using a helper, turn crankshaft with a wrench and observe voltage reading.
15. As distributor trigger wheel vane passes switch in distributor, voltage should be more than 1.8 volts. Between vanes, the voltage should be 0.0-0.7 volt. If voltage is other than specified, replace hall switch in distributor. Turn ignition off and disconnect multimeter.
16. Ensure ignition is off and disconnect ignition ECU connector. Attach multimeter negative (-) lead to ground and positive (+) lead to ECU connector pin No. 6. Turn ignition on and note voltage reading. Voltage should be approximately 12 volts. If no voltage is present, check continuity of wire and repair or replace as necessary.
17. Leave positive (+) lead attached to connector pin No. 6 and attach negative (-) lead to connector pin No. 20. Voltage reading should be approximately 12 volts. If no voltage is present, check ground connection at intake manifold.
18. Turn ignition off. Check continuity between distributor harness connector and ignition ECU connector as follows: Probe between distributor harness connector pin No. 1 and ECU connector pin No. 10. Probe between distributor harness connector pin No. 2 and ECU connector pin No. 24. Probe between distributor harness connector pin No. 3 and ECU connector pin No. 4. (Scheme 6) Resistance between all pins should be zero. (Scheme 6): Checking Distributor-to-Ignition ECU (Scheme 7): Ignition ECU & Fuel Distribution Rail Connector
19. Disconnect power stage connector. Attach multimeter leads between power stage connector pin No. 5 and ECU connector pin No. 16. Resistance should be zero. If continuity is present, replace ignition ECU. If continuity is not present, repair or replace wire. Reconnect power stage connector. Check ignition ECU connector pin No. 3 is not shorted to ground.
20. Ensure ignition is off. Attach multimeter negative (-) lead to ground and positive (+) lead to ECU connector pin No. 7. Resistance should be zero ohm. Depress accelerator pedal slightly. Resistance should increase but never be infinite. If resistance is not within specifications, check resistance at throttle switch to determine if switch is defective or if there is a broken wire(s).
21. Disconnect wiring harness from knock sensor. Attach a jumper wire to both terminals on back of knock sensor connector. Attach multimeter between ignition ECU connector pins No. 12 and 13. If resistance shows zero ohm, remove jumper wire from knock sensor connector. An infinity reading should now be present. If both checks fail, check for broken or shorted wire(s). NOTE: Visually check that circuit wire is connected to ECU connector pin No. 13 and that shield (ground) is connected to connector pin No. 12. Reversed connections will retard ignition timing and cause loss of power.
22. Measure voltage signal from fuel system ECU. Attach multimeter negative (-) lead to ground and positive (+) lead to ignition ECU connector pin No. 8. Turn ignition on. Voltage should be approximately 11 volts. If no voltage is present, check and repair wire between ignition ECU connector pin No. 8 and fuel system ECU connector pin No. 24. If wire and connections are okay, replace fuel system ECU.
23. Turn ignition off. If no faults were found in the previous steps and a problem still exists, install a new ignition ECU and/or power stage. Reconnect all disconnected components.

SPECIFICATIONS

TEMPERATURE SENSOR RESISTANCE

See also:
• TROUBLE SHOOTING - BASIC PROCEDURES