Ignition Coil: Testing and Inspection
Diagnostic Procedures
Ignition Coils With Power Output Stages, Checking
Special tools, testers and auxiliary items required
• Assembly tool (T10118)
• Hand multimeter (V.A.G 1526) or Multimeter (V.A.G 1715)
• Voltage tester (V.A.G 1527)
• Test adapter kit (V.A.G 1594)
• Wiring diagram
• Ignition coils and power output stages are one component and cannot be replaced individually.
Test Conditions
• Motronic Engine Control Module (ECM) Power Supply Relay (J271) -position 4- must be OK, check:
• Battery voltage (both batteries) must be at least 11.5 Volts.
• All electrical consumers such as, lights and rear window defroster must be switched off.
• For vehicles with automatic transmission, selector lever must be in " P".
• Parking brake must be engaged.
• The Ground (GND) connections between engine and body must be OK.
• Engine Speed (RPM) sensor must be OK, checking => [ Engine Speed Sensor, Checking ].
• Camshaft Position sensors must be OK, checking => [ Camshaft Position Sensor, Checking ].
• Ignition switched off.
• The OK:
Right instrument panel fuse holder
Test Sequence
- Remove engine covers.
- Remove both side parts of intake manifold.
- Disconnect the 4-pin connectors from ignition coils 1 through 12.
• Assembly tool (T10118) can be used to release connector catches.
• Before disconnecting harness connectors, mark allocation to component.
• Cylinder bank 1 with cylinders 1 through 6 is located at right in direction of travel.
• Cylinder bank 2 with cylinders 7 through 12 is located at left in direction of travel.
Checking voltage supply
- Check voltage supply between terminals 1 + 2 and 1 + 4 of the respective connector for ignition coils using the multimeter and adapter cables.
- Switch ignition on. Specification: at least 11.5 V
- Switch ignition off.
If no voltage is present:
- Check voltage supply at 4-pin connector terminal 1 according to wiring diagram:
- Check wires between 4-pin connector and Ground (GND) for open circuit according to wiring diagram. Terminal 2 and Ground (GND) terminal 4 and Ground (GND) wire resistance: max. 1.5 ohms
- Erase DTC memory of Engine Control Module => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09, Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code => [ Readiness Code, Generating ] Monitors, Trips, Drive Cycles and Readiness Codes.
If there is no malfunction in the voltage supply:
- Check activation.
Check activation
- Remove fuses 29 and 30 for fuel injectors 1 to 12 from fuse holder.
- Fuse holder in right of instrument panel.
- Connect voltage tester with adapter cables to terminal 3 + engine Ground (GND) on the disconnected connector for Ignition Coil 1 with Power Output Stage (N70), cylinder 1.
- Operate starter and test ignition signal from the corresponding Engine Control Module (ECM). LED must flicker
- Repeat test at connectors for ignition coils cylinder 2 through 12.
- Switch ignition off.
- Place fuses 29 and 30 for fuel injectors 1 to 12 back in the fuse holder.
- Fuse holder in right of instrument panel.
If LED flickers and voltage supply is OK:
- Replace respective ignition coils with power output stage, ignition coils with power output stages, removing and installing.
- Erase DTC memory of Engine Control Module (ECM) => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09, Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code => [ Readiness Code, Generating ] Monitors, Trips, Drive Cycles and Readiness Codes.
If LED does not flicker:
- Check wires to Engine Control Module according to wiring diagram.
Checking wires to Engine Control Module
Cylinder bank 1
- Connect test box to Engine Control Module (ECM) (J623) wiring harness on connecting test box for wiring test, refer to Repair Manual,
Cylinder bank 2
- Connect test box to E ngine Control Module (ECM) 2 (J624) wiring harness on connecting test box for wiring test, refer to Repair Manual,
Cylinder bank 1 and 2
- Check wires between test box and 4-pin connector to Engine Control Module for open circuit according to wiring diagram. Wiring resistance: max. 1.5 ohms
Cylinder bank 1
Cylinder bank 2
Cylinder bank 1 and 2
- Check wires for short circuit to B+ and Ground (GND). Specification: infinite ohms
- Erase DTC memory of Engine Control Module => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09, Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code => [ Readiness Code, Generating ] Monitors, Trips, Drive Cycles and Readiness Codes.
If there is no malfunction in wiring connections:
Cylinder bank 1
- Replace Engine Control Module (ECM) (J623).
Cylinder bank 2
- Replace Engine Control Module (ECM) 2 (J624).