Ignition Coil: Testing and Inspection
Ignition Coil with Power Output Stage, Checking
Observe all safety precautions: => [ Safety Precautions ] Generic Scan Tool
View clean working conditions: => [ Clean Working Conditions ] Clean Working Conditions
Use only gold-plated terminals when servicing any component with gold-plated electrical harness connector terminals.
For wiring diagrams, component locations, and connector views, Refer to the applicable wiring diagram.
Special tools, testers and auxiliary items required
• multimeter.
• Diode test lamp.
• Wiring diagram.
Test requirements
• The Ignition Coils with Power Output Stage (N70, N127, N291, N292, N323, N324) 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 => [ Preliminary Check ] Preliminary Check
Start diagnosis
- Remove the engine cover with air filter. Refer to appropriate service information.
- Remove the Ignition Coils with Power Output Stage (N70, N127, N291, N292, N323, N324) electrical harness screws - 1 -.
- Disconnect the Ignition Coils with Power Output Stage (N70, N127, N291, N292, N323, N324) electrical harness connectors - arrows - from the Ignition Coils with Power Output Stage (N70, N127, N291, N292, N323, N324).
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 Motronic Engine Control Module (ECM) Power Supply Relay (J271) terminal 8/87 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.
- 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
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, N83, N84) by removing Fuse 29 (on fuse panel B) from the fuse holder SB29, in the E-box, plenum chamber.
- 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, N323, N324). Refer to appropriate service 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.
If the manufacturers test box is not being used, perform the following step.
- Remove the Motronic Engine Control Module (ECM) (J623). Refer to appropriate service information.
- Using a multimeter, Check the Ignition Coil electrical harness connector to the Motronic 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.
- Check the wiring connection for damage, corrosion, loose or broken terminals.
- If necessary, repair the faulty wiring connection.
If the specified values were obtained:
- Replace the Motronic Engine Control Module (ECM) (J623). Refer to appropriate service information.
- Connect the Ignition Coils with Power Output Stage (N70, N127, N291, N292, N323, N324) electrical harness connectors - arrows - to the Ignition Coils with Power Output Stage (N70, N127, N291, N292, N323, N324).
- Install the Ignition Coils with Power Output Stage (N70, N127, N291, N292, N323, N324) electrical harness screws - 1 -.
- Install the engine cover with air filter. Refer to appropriate service information.
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 Modes 01 - 09.
2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.
3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.