The electronic ignition system controls fuel combustion by providing a spark to ignite the compressed air/fuel mixture at the correct time. To provide optimum engine performance, fuel economy, and control of exhaust emissions, the powertrain control module (PCM) controls the ignition system. The electronic ignition system has the following advantages over a mechanical distributor system:

The electronic ignition system does not use the conventional distributor and coil. The ignition system consists of the following components/circuits:

The PCM uses dual crankshaft position (CKP A and CKP B) sensors to determine crankshaft position. The CKP sensors are mounted in the engine block approximately 21.5 degrees apart from each other. Three wires connect each CKP sensor to the PCM. The PCM supplies an ignition voltage and a ground for each CKP sensor. During engine rotation, a slotted ring, machined into the crankshaft, causes the sensors to return a series of ON and OFF pulses to the PCM. The PCM uses these pulses to decode the position of the engine crankshaft.

The PCM uses two basic methods of decoding the engine position: Angle Based and Time Based, using either CKP A or CKP B sensor input. During normal operation, the PCM uses the Angle Based method. In order to operate in this mode, the PCM must receive signal pulses from both CKP sensors. The PCM uses the signal pulses to determine an initial crankshaft position, and to generate MEDRES (24X reference) and LORES (4X reference) signals. Once the initial crank position is determined, the PCM continuously monitors both sensors for valid signal inputs. As long as both signal inputs remain, the PCM will continue to use the Angle Based mode.

When either CKP signal is lost, the PCM will compare the MEDRES signal to the camshaft position (CMP) sensor signal. If the PCM detects a valid CMP signal, and the MEDRES to CMP signal correlation is correct, the PCM determines that CKP sensor A is at fault. However, if the MEDRES to CMP correlation is incorrect, the PCM determines that CKP sensor B is at fault.

If the PCM detects a loss of signal for CKP sensor A, DTC P0335 will set. The PCM will switch from Angle Based mode to Time Based mode B using CKP sensor B signal input. If the PCM detects a loss of signal for CKP sensor B, DTC P0385 will set. The PCM will switch from Angle based mode to Time Based mode A using CKP sensor B signal input. A noisy signal input from either CKP sensor will cause the ignition system to re-sync. If the number of ignition system re-sync is greater than a calibrated amount, DTC P1372 will set.

The camshaft position (CMP) sensor is mounted in the front of the right cylinder head assembly. The CMP sensor signal, when combined with the CKP sensor signal, enables the PCM to determine exactly which cylinder is on a firing stroke. The PCM can then properly synchronize the ignition system, fuel injectors, and knock control. The PCM supplies an ignition voltage and a ground for the CMP sensor. If a problem is detected with the CMP circuit, DTC P0340 or P0341 will set.

The electronic ignition system uses an individual ignition coil for each cylinder. There are two separate ignition module assemblies located in the camshaft cover of each cylinder bank. Each ignition module assembly contains an ignition control module and four ignition coils. Each ignition coil connects directly to a spark plug using a boot. This arrangement eliminates the need for secondary ignition wires. The ignition module assemblies receive power from a fused ignition feed. Both ignition module assemblies connect to chassis ground. A reference low and four ignition control (IC) circuits connect each ignition module assembly to the PCM. The PCM uses the individual IC circuits to control coil sequencing and spark timing for each ignition coil. The IC circuits transmit timing pulses from the PCM to the ignition control module to trigger the ignition coil and fire the spark plug. The PCM controls ignition system sequencing and timing events.

This ignition system produces very high energy to fire the spark plug. There is no energy loss because of ignition wire resistance, or the resistance of the waste spark system. Also, since the firing is sequential, each coil has seven ignition events to saturate as opposed to the three in a waste spark arrangement.

There are important considerations to point out when servicing the ignition system. The following noteworthy information will list some of these, to help the technician in servicing the ignition system.

The PCM is responsible for maintaining proper spark and fuel injection timing for all driving conditions. To provide optimum driveability and emissions, the PCM monitors input signals from the following components in calculating ignition control (IC) spark timing:

The reference low circuits provide a common ground between the PCM, and the ignition control modules. These circuits reduce the electrical ground shifts that may occur between the PCM and the ignition control modules. A malfunction in the reference low circuits may cause a poor driveability condition.

An ignition control circuit that is open, grounded, or short to voltage will set an ignition control circuit DTC. If a fault occurs in the IC output circuit when the engine is running, the engine will experience a misfire. DTCs P0351-P0358 indicate that a short to ground has been detected on an ignition control circuit. DTCs P1359 and/or P1360 will set when the PCM detects an open or a short to voltage in the ignition control circuit. If the malfunction is a short to voltage, a loss of two cylinders will occur.