Distributor Ignition (DI) System Description. Geo Prizm 1996

For 1990-2009 cars

The ignition system consists of the following components:

• | Distributor assembly

• | Camshaft position (CMP) sensor, or pick-up coil

• | Ignition control (IC) module

• | Ignition coil

The powertrain control module (PCM) provides the ignition timing signal for the vehicle ignition system. The PCM receives information on engine status from the engine sensors. The PCM then selects the most appropriate ignition timing settings from within the PCMs programming. The PCM sends a signal to the IC module. The ignition control module is connected to the negative side of the ignition coil's primary circuit. When the signal from the PCM is interrupted, the field around the primary coil collapses and a high voltage is induced in the secondary coil. The high voltage induced in the secondary coil is then forced to find a ground through the secondary (coil) wire, the rotor, the distributor cap, the secondary (spark plug) wires and across the spark plug gap to the engine block. The following are the most important inputs for determining ignition timing requirements:

• | The throttle position

• | The manifold pressure

• | The engine coolant temperature

• | Engine speed

### Noteworthy Ignition Information

Consider the following important information when servicing the ignition system:

• | The ignition coil's secondary output voltage is very high - 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 visible at the crankshaft pulley but are not used to set or adjust ignition timing. The powertrain control module provides all ignition timing adjustments electronically.

• | Be careful not to damage the secondary ignition wires or 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.