Ignition Coil: Testing and Inspection
Ignition Coils with Power Output Stage, Checking
The following procedure is used to diagnose all Ignition Coil with Power Output Stage (N70, N127, N291, N292, N323, N324).
Special tools, testers and auxiliary items required
• Multimeter.
• Diode test lamp.
• Wiring diagram.
Test requirements
• The Ignition Coils with Power Output Stage fuses OK.
• The Engine Component Power Supply Relay (J757) 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 => [ General Diagnosis ] General Diagnosis.
Start diagnosis
Recognize a nonfunctional or misfiring cylinder as follows:
- Compare the spark plugs of all the cylinders to each other. Check the electrodes for carbon fouling.
If faulty a cylinder is recognized:
- Switch the spark plug from the faulty cylinder with one from another cylinder.
If the malfunction follows the spark plug:
- Replace the spark plug.
If the malfunction remains at the original cylinder:
- Switch the ignition coil from the faulty cylinder with one from another cylinder.
If the malfunction follows the ignition coil:
- Replace the ignition coil.
Removal
- Remove the front engine cover - arrows -.
- Remove the rear engine cover - arrows -.
Cylinder bank 1 (right)
- Remove the air duct screws - arrows -.
- Remove the air ducts - 1 - and - 2 -.
- Remove the check valve - 1 - from the air duct hose.
- Loosen the hose clamp - 2 -, release the retaining clips - arrows -, and remove the air duct hose.
- Disconnect the electrical harness connectors from the following:
1. Engine Coolant Temperature (ECT) Sensor (G62 )
2. Intake Manifold Flap Change-over Valve (N239 )
3. Intake Manifold Tuning (IMT) Valve Position Sensor (P2076) (G513)
- Disconnect the electrical harness connectors from the following:
1. Camshaft Adjustment Valve 1 (exhaust) (N318).
2. Camshaft Adjustment Valve 1 (N205).
3. Camshaft Position (CMP) Sensor (G40).
4. Intake Manifold Runner Position Sensor (G336 ).
5. Camshaft Position (CMP) Sensor 3 (G300).
- Remove the screws - arrows - and disconnect the electrical connections at the ignition coils.
Cylinder bank 2 (left)
- Remove the screw - arrow - retaining the coolant reservoir.
- Disconnect the electrical connector from the Engine Coolant Level (ECL) Warning Switch (F66) at the bottom of the coolant reservoir and set aside the coolant reservoir with the coolant hoses - 1 - and - 2 - connected.
- Disconnect the electrical connector from the high pressure fuel pump - 2 -.
- Disconnect the electrical harness connectors from the following:
1. Camshaft Position (CMP) Sensor 2 (G163).
2. Camshaft Adjustment Valve 2 (N208).
3. Camshaft Adjustment Valve 2 (exhaust) (N319).
4. Camshaft Position (CMP) Sensor 4 (G301).
- Remove the screws - arrows - and disconnect the electrical connections at the ignition coils.
Checking voltage supply
- Switch the ignition on.
- Using a Multimeter, check the Ignition Coil electrical harness connector terminals 1 to 4 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 Engine Component Power Supply Relay (J757) socket 4/85 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 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 activation
CAUTION!
Do not touch the Ignition Coils connecting parts or adapter cables during the following test.
- Disable the power supply to the Fuel Injectors ( N30, N31, N32, N33) by removing the necessary fuse.
- 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 Coils with Power Output Stage (N70, N127, N291, N292) Refer to Fuel Injection and Ignition Repair Information.
If the LED does not flicker:
Checking wiring
If the manufacturers test box is being used. Perform the following step.
- Install the test box. Refer to Fuel Injection and Ignition Repair Information.
If the manufacturers test box is not being used. Perform the following step.
- Remove the Engine Control Module (ECM) (J623 ). Refer to => [ ECM, Removing and Installing ] ECM, Removing and Installing.
- Using a Multimeter, Check the Ignition Coil electrical harness connector to the Engine 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 => [ ECM, Removing and Installing ] ECM, Removing and Installing.
Assembly is performed in the reverse order of removal, note the following:
Final procedures
After repair work, the following work steps must be performed in the following sequence:
1. Check the DTC memory. => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Mode 03 - Read DTC Memory.
2. If necessary, erase the DTC memory. => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.
3. If the DTC memory was erased, generate readiness code. => [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.
- End diagnosis and switch ignition off.