Ignition Coil: Testing and Inspection
Ignition Coil with Power Output Stage, Checking
The following procedure is used to diagnose Ignition Coil with Power Output Stage (N70, N127, N291, N292, N323).
Special tools, testers and auxiliary items required
• Multimeter
• wiring diagrams
• Low current voltage tester
• The ignition coils and power output stages are one component and cannot be replaced individually.
Test requirement
The fuses for the engine electronics OK.
Test procedure
- Perform a preliminary check to verify the customers complaint. Refer to => [ Preliminary Check ] Preliminary Check.
Start diagnosis
Check for a misfiring cylinder as follows:
- For ease of fault location (i.e. Cyl 1, Cyl 2 etc.) use basic scan tool to isolate affected cylinder.
- Compare the spark plugs of all the cylinders to each other. Check the electrodes for carbon fouling.
If a faulty 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.
Electrical harness removal
- Pull engine cover out of first mount at front arrow 1, then at right rear arrow 2 and finally at left rear arrow 3.
- Disconnect the electrical harness connectors- A - from the ignition coils:
Checking voltage supply
- Using the Low current voltage tester, check the following wiring connections for voltage.
Checking resistance
- Using a Multimeter, check the following wiring connection for an open circuit.
Specified resistance 1.5 ohms max.
- If necessary, repair the wiring connection.
- Switch the ignition on.
- Using the Multimeter, check the following wiring connection for voltage.
Specified value: approx. battery voltage
- Switch the ignition off.
If the specified value is obtained:
Checking activation of power output stages
- Remove the rubber seal in the direction of the - arrow -.
- Remove the plenum chamber cover - 1 -.
- Using a screwdriver, remove wiper arm caps- 3 - from wiper arms.
- Loosen wiper arm nuts - 4 - several turns.
- Loosen wiper arms - 2 - from wiper axle by tilting slightly.
- Remove wiper arm nuts completely and remove wiper arms.
- Remove securing clips - 1 - and cowl - 5 -.
- Remove the screws - arrows - and cover from the E-Box in the plenum chamber.
- Using a screwdriver, remove the retainer bar - arrow - and Engine Control Module (ECM) (J623) and position aside.
- Remove the Motronic Engine Control Module (ECM) Power Supply Relay (J271) - 2 - from the E-Box.
- Using the Multimeter, check the wiring connection from the Motronic Engine Control Module (ECM) Power Supply Relay (J271) carrier position 2, terminal 2 to the ignition coil wiring harness electrical connector terminal 1 for an open circuit.
Specified resistance 1.5 ohms max.
If the specified value is not obtained:
- Repair the wiring connection.
If no malfunctions are found in the wiring:
If the manufacturers test box is being used. Perform the following step.
- Install the Adapter Cable (121 Pin) (VAG1598/31 ).
Specified resistance 1.5 ohms max.
If the specification is not obtained:
- Repair the wiring connection.
If no malfunctions are found in the wiring:
- Replace the faulty ignition coil..
- 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 ] Readiness Code.
- End diagnosis.
If the DTC does return and no malfunction is detected in the wiring and the voltage supply was OK:
- Replace the Motronic Engine Control Module (ECM) (J623). Refer to => [ Motronic Engine Control Module, Replacing ] Motronic Engine Control Module, Replacing.
- 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, Setting ] Readiness Code, Setting.
End of Diagnosis.