Ignition Coil: Testing and Inspection

Ignition Coils with Power Output Stage (N70, N127, N291, N292), checking

The following procedure is used to diagnose all Ignition Coils with Power Output Stage.

Special tools, testers and auxiliary items required

• Multimeter.

• Diode test lamp.

• Wiring diagram.

Test requirements

• The Spark Plugs OK.

• Fuse (SB8) fuses 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 => [ Engine Control Module (ECM) (J623), replacing ] Engine Control Module (ECM) (J623).

Start diagnosis

- Remove the engine cover with air filter.

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





- Disconnect the Ignition Coil electrical harness connectors - arrows - from the Ignition Coil.





Checking voltage supply

- Switch the ignition on.

- Using a Multimeter, check the Ignition Coil electrical harness connector terminals 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 the Motronic Engine Control Module (ECM) Power Supply Relay (J271) terminal 2/87 for resistance.

Specified value: 1.5 ohms Max.

If the specified value was not obtained:

- Check the Ignition Coil electrical harness connector terminal 1 to the Motronic Engine Control Module (ECM) Power Supply Relay (J271) terminal 2/87 for an open circuit, short circuit to Battery (+) or Ground (GND).

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

- If necessary, repair the faulty wiring connection.

If the specified values were obtained:

Checking activation

Do not touch the Ignition Coils connecting parts or adapter cables during the following test.

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





- Operate the starter.

The LED should flicker.

- Switch the ignition off.

If the LED flickers and the voltage was OK:

- Replace the faulty Ignition Coil.

If 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 Engine Control Module (ECM) (J623). Refer to => [ Engine Control Module (ECM) (J623), replacing ] Engine Control Module (ECM) (J623).

- Using a Multimeter, Check the Ignition Coil electrical harness connector terminals to the Engine Control Module (ECM) (J623) electrical harness connector T60 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, loose or broken terminals.

- If necessary, repair the faulty wiring connection.

If the specified values were obtained:

- Erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.

- Perform a road test to verify repair.

If the DTC does not return:

Repair complete, Generate readiness code. Refer to => [ Readiness Code ] Engine.

- End diagnosis.

If the DTC does return and no malfunction is detected in the wiring and the voltage supply was OK:

- Replace the Engine Control Module (ECM) (J623). Refer to => [ Engine Control Module (ECM) (J623), replacing ] Engine Control Module (ECM) (J623).

- Assembly is performed in the reverse of the removal.

Final procedures

After the 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 ] 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 ] Engine.

End of diagnosis