For 1990-2009 cars

#### Ignition Coils

(1) | Ignition Coil 1
(2) | Ignition Coil 2
(3) | Ignition Coil 3
(4) | Ignition Coil 4

The electronic ignition system is of the direct ignition system (DIS) type and is controlled by the powertrain control module (PCM). The electronic ignition system is composed of the following components:

• | The PCM

• | The 4 ignition coil assemblies

• | The crankshaft position (CKP) sensor

• | The camshaft position (CMP) sensor

• | The spark plugs

The electronic ignition system provides the following benefits:

• | Improved ignition timing accuracy

• | Reduced high-voltage losses

• | Enhanced overall ignition system reliability

The electronic ignition system components cannot be disassembled or repaired. A component that is correctly diagnosed as faulty must be replaced as a complete unit.

### Operation

The powertrain control module (PCM) uses reference pulses from the crankshaft position (CKP) sensor in order to determine the engine speed. The PCM cannot operate the ignition system or the fuel injectors without the engine speed signal from the CKP. The PCM controls the ignition timing by controlling the ignition coils.

Each ignition coil has a built-in ignition module that controls the current flow in the primary coil winding. When the current flow is interrupted, the electrical field around the primary coil collapses and a high voltage is induced in the secondary coil. The secondary coil voltage travels from the coil output terminal, through the spark plug boot, and across the spark plug gap to the engine block. As a fail-safe function the ignition control module sends an ignition confirmation signal back to the PCM whenever the primary field collapses.

The camshaft position (CMP) sensor input is used to detect an engine misfire. The PCM also uses the CMP sensor signal as an input for modifying the fuel injection timing and for modifying the ignition timing.

The PCM receives information on the engine status from various engine sensors and then selects the most appropriate ignition timing settings from within the PCM's programming. The following are the most important inputs for determining ignition timing requirements:

• | The engine speed

• | The throttle position (TP)

• | The intake air volume

• | The engine coolant temperature (ECT)

• | The knock sensor (KS) input

### Crankshaft Position (CKP) Sensor

The crankshaft position (CKP) sensor is located in the front cover of the cylinder block near the crankshaft pulley. The CKP sensor produces an AC signal that increases in both frequency and amplitude as the engine speed increases. The CKP sensor signal is sent to the PCM in order to indicate the RPM and the crankshaft position. The PCM uses the CKP sensor signal along with the camshaft position (CMP) sensor signal for the following purposes:

• | To calculate the fuel injector pulse

• | To establish the piston position top dead center (TDC) for the ignition timing

• | To start the ignition coil and fuel injection sequencing

### Operation

The CKP sensor signal rotor has 34 teeth and is mounted on the crankshaft behind the timing chain cover and the crankshaft pulley. When the crankshaft rotates, the CKP sensor signal rotor teeth pass by the CKP sensor causing a fluctuation in the sensors magnetic field. The fluctuation in the magnetic field induces a voltage in the CKP sensor circuitry. The sensor sends this signal to the PCM at rate of 34 signals per crankshaft revolution.

### Camshaft Position (CMP) Sensor

The camshaft position (CMP) sensor is located in the cylinder head near the number 4 fuel injector. The CMP sensor is a signal generator that is composed of a magnet and a coil with an iron core. The PCM relies on the AC signal provided by the CMP sensor in order perform the following:

• | To optimize the ignition timing

• | To optimize the fuel delivery

• | To detect any engine misfire

• | To monitor CMP actuator solenoid valve operation

### Operation

The CMP sensor signal rotor (2) is part of the intake camshaft (1) and has 3 teeth located on the outer circumference. When the CMP sensor signal rotor (2) rotates past the CMP sensor (3), electrical signals are generated. The AC signals that are generated by the CMP sensor are sent to the PCM.

### Knock Sensor (KS)

The knock sensor (KS) is located below the intake manifold, between cylinder 2 and cylinder 3, on the engine block. The KS (1) detects engine detonation and sends a signal to the PCM. The PCM uses the input from the KS to adjust the ignition timing in order to control detonation. For detailed information on the operation of the KS refer to Knock Sensor (KS) System Description .

### Noteworthy Ignition Information

Consider the following important information when servicing the ignition system:

• | The ignition coils secondary output voltage is more than 40,000 volts. Avoid body contact with the ignition high voltage secondary components when the engine is running or personal injury may result.

• | The ignition timing is not adjustable. A timing indicator and timing marks are still visible at the crankshaft pulley but are not used to set or adjust the ignition timing. The PCM provides all ignition timing adjustments electronically.

• | Be careful not to damage the secondary ignition boots when servicing the ignition system. Rotate each ignition wire boot in order to loosen the boot from the spark plug before removing the wire. Never pierce a secondary ignition wire or boot for any testing purposes. Future ignition system problems are guaranteed if pinpoints or test lights are pushed through the secondary ignition wire insulation during component testing.

• | Do not use a conventional tachometer in order to check the engine speed on this ignition system. An inductive type pick-up will not provide reliable engine speed information. Use a scan tool in order to monitor the engine RPM.