Ignition Coil: Testing and Inspection

Ignition Coils with Power Output Stage, Checking

Ignition Coils with Power Output Stage, Bank 1

The following procedure is used to diagnose the Ignition Coils with Power Output Stage (N70, N127, N291, N292).

Special tools, testers and auxiliary items required

• Multimeter.

• Diode test lamp.

• Wiring diagram.

Test requirements

• Fuse (SC3) OK.

• The Motronic Engine Control Module (ECM) Power Supply Relay (J271) OK.

• The Engine Speed (RPM) Sensor (G28) OK.

• The Camshaft Position (CMP) Sensor (G40) OK.

• Battery voltage at least 12.5 volts.

• All electrical consumers such as, lights and rear window defroster, switched off.

• Vehicles with automatic transmission, shift selector lever into position " P" or "N".

• A/C switched off.

• Ground (GND) connections between engine/transmission/chassis OK.

• Ignition switched off.

Test procedure

- Perform a preliminary check to verify the customers complaint. Refer to => [ Preliminary Check ] Preliminary Check.

Start diagnosis

- Remove the rear engine cover - arrows -.

- Remove the vacuum lines - 3 - and - 4 - from the air guide hose.

- Disconnect the Mass Air Flow (MAF) Sensor (G70) electrical harness connector - 1 -.

- Loosen the hose clamps - 2 - and - 5 - and remove the air guide hose.

- Remove the Ignition Coil electrical harness screws- 1 - and - 2 -.

- Disconnect the Ignition Coil electrical harness connectors from the Ignition Coils with Power Output Stage - 3,4,5,6 -.

Checking voltage supply

- Crank the engine.

- Using a Multimeter, check the Ignition Coil electrical harness connector terminal 1 to Ground (GND) for voltage.

Specified value: battery voltage.

- Switch the ignition off.

If the specified value was not obtained:

- Check the Ignition Coil electrical harness connector terminal 1 to theMotronic Engine Control Module (ECM) Power Supply Relay (J271) socket 2/87 for resistance.

Specified value: 1.5 ohms Max.

If the specified value was not obtained:

- Check the wiring connection for an open circuit, short circuit to Battery (+) or Ground (GND).

- Check the wiring connection for damage, corrosion, lose or broken terminals.

- If necessary, repair the faulty wiring connection.

If the specified values were obtained:

Checking Ground (GND)

- Using a Multimeter, check the Ignition Coil electrical harness connector terminal 2/31 to Ground (GND) 2 on the right "A" pillar for resistance.

Specified value: 1.5 ohms Max.

If the specified value was not obtained:

- Check the wiring connection for an open circuit or short circuit to Battery (+).

- Check the wiring connection for damage, corrosion, lose or broken terminals.

- If necessary, repair the faulty wiring connection.

If the specified values were obtained:

- Using a Multimeter, check the Ignition Coil electrical harness connector terminal 4/31 to Ground (GND) 2 on the intake manifold for resistance.

Specified value: 1.5 ohms Max.

If the specified value was not obtained:

- Check the wiring connection for an open circuit or short circuit to Battery (+).

- Check the wiring connection for damage, corrosion, lose or broken terminals.

- If necessary, repair the faulty wiring connection.

If the specified values were obtained:

Checking activation

CAUTION!
Do not touch the Ignition Coils with Power Output Stage connecting parts or adapter cables during the following test.

- Disable the power supply to the Fuel Injectors.

- Using a diode test lamp, check the Ignition Coil electrical harness connector terminals 3 to 2/31 for voltage.

- Crank the engine.

The LED should flicker.

- Switch the ignition off.

If the LED flickers and the voltage was OK:

- Replace the faulty Ignition Coil with Power Output Stage.

The LED does not flicker:

Checking wiring

If the manufacturers test box is being used. Perform the following step.

- Install the test box.

If the manufacturers test box is not being used. Perform the following step.

- Remove the Motronic Engine Control Module (ECM) (J623). Refer to => [ Engine Control Module, Removing and Installing ]Service and Repair.

- Using a Multimeter, Check the Ignition Coil electrical harness connector to theEngine Control Module (ECM) (J623) electrical harness connector T60 for an open circuit.

Specified value: 1.5 ohms Max.

If the specified value was not obtained:

- Check the wiring connection for an open circuit, short circuit to Battery (+) or Ground (GND).

- Check the wiring connection for damage, corrosion, lose or broken terminals.

- If necessary, repair the faulty wiring connection.

If the specified values were obtained:

- Replace the Engine Control Module (ECM) (J623). Refer to => [ Engine Control Module, Removing and Installing ]Service and Repair.

Assembly is performed in the reverse order of removal.

Final procedures

After repair work, the following work steps must be performed in the following sequence:

1. Check the DTC memory. Refer to => [ Diagnostic Mode 03 - Read DTC Memory ].

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ]Diagnostic Mode 04 - Erase DTC Memory.

3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.

- End of diagnosis.

Ignition Coils with Power Output Stage, Bank 2

The following procedure is used to diagnose the Ignition Coils with Power Output Stage (N323, N324, N325, N326).

Special tools, testers and auxiliary items required

• Multimeter.

• Diode test lamp.

• Wiring diagram.

Test requirements

• Fuse (SC3) OK.

• The Motronic Engine Control Module (ECM) Power Supply Relay (J271) OK.

• The Engine Speed (RPM) Sensor (G28) OK.

• The Camshaft Position (CMP) Sensor (G40) OK.

• Battery voltage at least 12.5 volts.

• All electrical consumers such as, lights and rear window defroster, switched off.

• Vehicles with automatic transmission, shift selector lever into position " P" or "N".

• A/C switched off.

• Ground (GND) connections between engine/transmission/chassis OK.

• Ignition switched off.

Test procedure

- Perform a preliminary check to verify the customers complaint. Refer to => [ Preliminary Check ] Preliminary Check.

Start diagnosis

- Remove the oil dipstick - 1 - from the guide tube.

- Remove the Ignition Coil electrical harness screws- 2 - and - 3 -.

- Disconnect the Ignition Coil electrical harness connectors from the Ignition Coils with Power Output Stage - 1,2,3,4 -.

Checking voltage supply

- Crank the engine.

- Using a Multimeter, check the Ignition Coil electrical harness connector terminal 1 to Ground (GND) for voltage.

- Crank the engine.

The LED should flicker.

- Switch the ignition off.

If the LED flickers and the voltage was OK:

- Replace the faulty Ignition Coil with Power Output Stage.

The LED does not flicker:

Checking wiring

If the manufacturers test box is being used. Perform the following step.

- Install the test box.

If the manufacturers test box is not being used. Perform the following step.

- Remove the Motronic Engine Control Module (ECM) (J623). Refer to => [ Engine Control Module, Removing and Installing ] Engine Control Module.

- Using a Multimeter, Check the Ignition Coil electrical harness connector to theEngine Control Module (ECM) (J623) electrical harness connector T60 for an open circuit.