Location of components
| Item name | Spare part number | Description |
| 1 | - | Spark plug |
| 2 | - | Ignition coil |
| 3 | - | spark plug wire |
| 4 | - | Capacitor |
General information
The 4.0L engine's ignition system has one platinum-tipped spark plug per cylinder. Each spark plug is powered by a separate ignition coil. The three ignition coils for each cylinder bank are grouped on the corresponding side of the intake manifold. The ignition coils are directly actuated by the engine control unit (ECM).
Power is supplied to the ignition coils through the main relay and fuse in the battery electrical junction box (BJB).
Each ignition coil has a power transistor that turns on the primary winding. The ECM controls the switching with a signal applied to the power transistor. A capacitor connected in parallel to the ignition coil power supplies serves to suppress radio frequency interference. The ECM controls the operation of the ignition coils using a feedback signal from the power circuit of each of the coils. When a fault is detected, the ECM stores the appropriate fault code.
Depending on the battery voltage and engine speed, the ECM adjusts the duration of the primary circuit to ensure that the discharge energy generated in the secondary is constant. This allows for good sparking without overloading the primary circuit by current and overheating of the ignition coils.
The ECM calculates the ignition timing for the cylinders based on the following data:
- Engine crankshaft speed.
- Camshaft position.
- Engine load.
- Coolant temperature.
- Tendency to detonate.
- On vehicles with automatic transmission, the position of the selector is taken into account.
- Idling requirements are taken into account.
Ignition control circuit
NOTE: A = Wired connections
| Item name | Spare part number | Description |
| 1 | - | Accumulator battery |
| 2 | - | Fuse link 11E in BJB block |
| 3 | - | ignition switch |
| 4 | - | Fuse 25P, ignition supply, in the central electrical box (CJB) |
| 5 | - | Fuse 60P, power to start, in CJB |
| 6 | - | ECM |
| 7 | - | Ignition coil 6 |
| 8 | - | Ignition coil 5 |
| 9 | - | Ignition coil 4 |
| 10 | - | Capacitor |
| 11 | - | Ignition coil 1 |
| 12 | - | Ignition coil 2 |
| 13 | - | Ignition coil 3 |
| 14 | - | Fuse 17E in BJB |
| 15 | - | Main relay |
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