Electronic Ignition (EI) System Description. Oldsmobile Intrigue 1998

For 1990-2009 cars only

Makes 🢒 Oldsmobile 🢒 1998 🢒 Intrigue 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 Electronic Ignition (EI) System Description

Purpose

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 PCM controls the spark advance of the ignition system. Electronic ignition has the following advantages over a mechanical distributor system:

•	No moving parts.

•	Less maintenance.

•	Remote mounting capability.

•	No mechanical load on the engine.

•	More coil cool down time between firing events.

•	Elimination of mechanical timing adjustments.

•	Increased available ignition coil saturation time.

Operation

The electronic ignition system does not use the conventional distributor and coil. The ignition system consists of 3 ignition coils, an ignition control module (ICM), a dual Hall-effect crankshaft position (CKP) sensor, an engine crankshaft balancer with interrupter rings attached to the rear, the related connecting wires, and the Ignition Control (IC) and fuel metering portion of the PCM.

Conventional ignition coils have one end of the secondary winding connected to the engine ground. However, in this ignition system, neither end of the secondary winding is grounded. Instead, each end of a coil's secondary winding is attached to each spark plug of the 2 cylinders designated to share the coil (1/4, 2/5, 3/6). These 2 cylinders are referred to as companion cylinders, i.e., on top dead center at the same time. When the coil discharges, both plugs fire at the same time to complete the series circuit. The cylinder on compression is said to be the event cylinder and the one on exhaust is the waste cylinder. The cylinder on the compression stroke requires most of the secondary coil's available voltage to fire the spark plug. The remaining energy is used as required by the cylinder on the exhaust stroke. The same process is repeated when the cylinders reverse roles. This type of ignition is called a waste spark ignition system.

On a conventional ignition system the spark plugs fire with the same polarity (forward). If the polarity of the conventional ignition system was reversed, the spark plugs would fire backwards. Since the required voltage to fire the spark plugs backwards is higher, and coil design limited the secondary coil's available voltage, a weak spark or misfire could occur. However, in the waste spark ignition system, the polarity of the ignition coil primary and secondary windings is fixed. One spark plug always fires with normal polarity and its companion plug fires with reverse polarity. The voltage required by each spark plug is determined by the polarity and the cylinder pressure. The cylinder on the compression stroke requires more voltage to fire the spark plug than the cylinder on the exhaust stroke. Because of improved coil design, and increased primary current flow and saturation time, the ignition coils produce a higher secondary voltage - greater than 40 kilovolts (40,000 volts) at any engine RPM. The higher available voltage provides more than enough energy required by the event cylinder, the additional spark plug gap, and the reverse polarity of the waste cylinder.

It is possible for one spark plug to fire even though a plug wire from the same coil may be disconnected from its companion plug. The disconnected plug wire acts as one plate of a capacitor, with the engine being the other plate. These 2 capacitor plates are charged as a spark jumps across the gap of the connected spark plug. The plates are then discharged as the secondary energy is dissipated in an oscillating current across the gap of the spark plug that is still connected. Secondary voltage requirements are very high with an open spark plug or spark plug wire. The ignition coil has enough reserve energy to fire the plug that is still connected at idle, but the coil may not fire the spark plug under high engine load. A more noticeable misfire may be evident under load as both spark plugs may then be misfiring.

System Components

Crankshaft Position Sensor and Crankshaft Balancer Interrupter Rings

The dual crankshaft position (CKP) sensor is secured in an aluminum mounting bracket and bolted to the front left side of the engine timing chain cover, partially behind the crankshaft balancer. A 4-wire harness connector plugs into the sensor, connecting the sensor to the ignition control module (ICM) . The dual crankshaft position sensor contains 2 Hall-effect switches with one shared magnet mounted between them. The magnet and each Hall-effect switch are separated by an air gap. A Hall-effect switch reacts like a solid state switch, grounding a low current signal voltage when a magnetic field is present. When the magnetic field is shielded from the switch by a piece of steel placed in the air gap between the magnet and the switch, the signal voltage is not grounded. If the piece of steel (called an interrupter) is repeatedly moved in and out of the air gap, the signal voltage appears to oscillate on and off repeatedly. In the case of the electronic ignition system, the piece of steel is 2 concentric interrupter rings mounted to the rear of the crankshaft balancer.


(1)	Crankshaft Balancer
(2)	Interrupter Rings

Each interrupter ring has blades and windows that either block the magnetic field or allow the field to close one of the Hall effect switches. The outer Hall effect switch produces a signal called the CKP 18X because the outer interrupter ring has 18 evenly spaced blades and windows. The CKP 18X portion of the crankshaft position sensor produces 18 ON/OFF pulses per crankshaft revolution. The Hall-effect switch closest to the crankshaft, the CKP sync portion of the sensor, produces a signal that approximates the inside interrupter ring. The inside interrupter ring has 3 unevenly spaced blades and windows of different widths. The CKP sync portion of the CKP sensor produces 3 different length ON/OFF pulses per crankshaft revolution. When a CKP sync interrupter ring window is between the magnet and inner switch, the magnetic field causes the CKP sync Hall effect switch to ground the CKP sync signal voltage supplied from the ignition control module. The CKP 18X interrupter ring and Hall-effect switch react similarly. The ignition control module interprets the CKP 18X and CKP Sync ON/OFF signals as an indication of the crankshaft position, and the ignition control module must have both signals to fire the correct ignition coil. The ignition control module determines the crankshaft position for correct ignition coil sequencing by counting how many CKP 18X signal transitions occur, i.e.; ON/OFF or OFF/ON, during a CKP sync pulse.

Camshaft Position (CMP) Sensor

The camshaft position (CMP) sensor is located on the timing cover behind the water pump near the camshaft sprocket. The CMP sensor contains a Hall effect switch. A magnet, mounted on the camshaft sprocket, activates the Hall effect switch in the CMP sensor. When activated, the Hall effect switch pulls the CMP signal voltage low. The ICM interprets the low voltage as a CMP Sensor signal. The CMP sensor signal is created as piston #1 is approximately 25 degrees after top dead center on the power stroke. The ICM passes the CMP signal to the PCM for true sequential fuel injection.

Ignition Control Module and Ignition Coil


(1)	Screws
(2)	Ignition Coil
(3)	Ignition Control Module

Ignition Coils

Three twin-tower ignition coils are individually mounted to the ignition control module. Each coil provides spark for 2 plugs simultaneously (waste spark distribution). Each coil is serviced separately. Two terminals connect each coil pack to the module. Each coil is provided a fused ignition feed. The other terminal at each coil is individually connected to the module, which energizes one coil at a time by completing and interrupting the primary circuit ground path to each coil at the proper time.

Ignition Control Module (ICM)

The ignition control module performs the following functions:

•	Power the dual CKP sensor internal circuits.

•	Supply the voltage signals that each respective Hall effect switch pulses to ground to generate the CKP sync and CKP 18X signal pulses.

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Determine the correct ignition coil firing sequence, based upon how many CKP 18X signal transitions occur during a CKP sync pulse. This coil sequencing occurs at start-up. After the engine is running, the module stores the sequence, and continues triggering the ignition coils in the proper sequence. If the CKP sync pulses are missing at start-up, the ignition control module is unable to determine the proper ignition coil sequence and a loss of spark occurs. However, normal fuel injector pulses occur.

•	Determine whether or not the crankshaft is rotating in the proper direction, and cuts off fuel delivery and spark to prevent backfiring if reverse rotation is detected.

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The ignition control module sends the 3X reference and 18X reference signals to the PCM. The PCM determines crankshaft position and engine RPM from these signals. The PCM uses these signals for ignition control (IC) spark timing calculations. The falling edge of each 3X and 18X reference pulse occurs at a specific time in relation to top dead center of any cylinder stroke. The 3X reference signal is an ON/OFF pulse occurring 3 times per crankshaft revolution. The 3X reference signal is not the CKP sync pulse. To produce the 3X reference signal, the ignition control module receives the 18X CKP signal, and processes the signal through an internal divide-by-6 circuitry. If the 18X CKP signal is missing at start-up, the ignition control module is unable to generate the 18X or 3X reference signals, and a loss of spark and fuel injection occurs.


(1)	Knock Sensor (KS) Module Cover
(2)	Connector C1 (Blue)
(3)	Connector C2 (Clear)

Powertrain Control Module (PCM)

The PCM is responsible for maintaining proper spark timing to ensure optimum driveability and emissions control. The PCM uses the ignition control (IC) spark timing method to calculate spark advance and ignition dwell over a wide range of engine speeds and loads. The PCM calculates IC spark timing based on input signals from the following components:

•	The 24X crankshaft position sensor reference.

•	The ignition control module (ICM).

•	The engine coolant temperature (ECT) sensor.

•	The engine knock sensors (KS).

•	The intake air temperature (IAT) sensor.

•	The mass air flow (MAF) sensor.

•	The transaxle range or park/neutral position (PNP) switches.

•	The vehicle speed sensor (VSS) / transaxle output speed sensor (TOSS).

The ignition system uses many of the same ignition module-to-PCM circuits as did previous Delco engine management systems using distributor type ignition. The following describes the PCM to ignition control module circuits:

•	The 3X reference PCM input:

The ignition control module (ICM) generates the 3X reference signal from the 18X CKP sensor. To generate the 3X reference signal, the ICM processes the 18X CKP signal through divide-by-6 circuit. The ICM then sends the 3X reference signal to the PCM. The PCM uses this signal to calculate engine speed and crankshaft position at engine speeds above 1280 RPM (± 150 RPM).

•	The 18X reference PCM input

The 18X CKP sensor generates the 18X reference signal. The PCM uses the signal to calculate engine speed and crankshaft position at engine speeds below 1280 RPM (±150 RPM). The 18X reference signal provides better signal resolution within the calibrated RPM range. This increases idle quality and low speed driveability.

•	The camshaft position (CMP) PCM input

The PCM uses this signal to determine the position of the cylinder #1 piston during the piston's power stroke. This signal is used by the PCM to calculate a true sequential fuel injection (SFI) mode of operation. The PCM compares the number of CAM pulses to the number of 18X and 3X reference pulses. If the number of 18X and 3X reference pulses occurring between CAM pulses is incorrect, or if no CAM pulses are received while the engine is running, the PCM sets DTC P0341. If the cam signal is lost while the engine is running the fuel injection system shifts to a calculated SFI mode based on the last cam pulse, and the engine continues to run. The engine can be re-started and runs in the calculated sequential mode as long as the condition is present with a 1 in 6 chance of being correct.

•	The reference low PCM input

The reference low circuit establishes a common ground between the ignition control module and the PCM. This circuit minimizes electrical ground differences between the PCM and the ignition control module. The PCM uses the reference low circuit in order to clearly recognize the 3X and 18X reference signals. A malfunction in the reference low circuit may result in a reduced driveability condition.

•	Bypass signal PCM output

The PCM continuously sends ignition control (IC) spark timing pulses on the IC circuit. However, during start-up, the ignition control module (ICM) grounds the IC spark timing pulses, and maintains spark timing fixed at 10° BTDC. The fixed spark timing is maintained until the engine speed is above a specific RPM and the PCM receives a calibrated number of 3X reference pulses from the ICM (Bypass Mode). Once the PCM receives the 3X reference pulses, the PCM applies 5 volts to the ICM on the bypass circuit. The bypass voltage signals the ICM to transfer IC spark timing to the PCM (IC Mode). The ICM switches the IC pulses from ground allowing the PCM to control spark timing. If the PCM does not apply 5 volts to the bypass circuit, or if the ICM does not sense the 5 volts, the ICM continues to control spark timing (Bypass Mode). In the Bypass mode, the ICM determines the proper ignition coil sequence and spark timing.

•	Ignition Control (IC) PCM output

The PCM continuously sends out ignition control (IC) timing pulses to the ignition control module (ICM) on the IC circuit. When the ignition system is in the Bypass mode (PCM has not sent the 5 volt Bypass signal), the ICM grounds these pulses and maintains a fixed spark timing of 10° BTDC. When the engine speed reaches a specific RPM and PCM receives the calibrated number of 3X reference pulses from the ICM, the PCM sends the Bypass signal. The bypass voltage signals the ICM to transfer spark timing control to the PCM (IC Mode). The ICM switches the IC pulses from ground allowing the PCM to control ignition dwell and spark timing. In the IC Mode, the ICM always determines the proper coil sequence while the PCM controls the IC spark timing.

Ignition System Modes of Operation

The PCM continuously sends out ignition control (IC) timing pulses to the ignition control module (ICM) on the IC circuit. Anytime the PCM does not apply 5 volts to the ignition control module (ICM) bypass circuit, the ICM controls ignition timing. The ICM fires each of the three coils in the proper sequence at a fixed timing of 10° BTDC. This mode of operation is called the Bypass Mode.

When engine speed reaches a specific value and the PCM receives the calibrated number of 3X reference pulses, the PCM applies 5 volts to the ICM on the bypass circuit. This signals the ICM to transfer spark timing control to the PCM. This mode of operation is called the IC Mode. During the IC Mode, the PCM controls spark advance and dwell to compensate for a wide range of engine speeds and loads.

In the IC Mode, the PCM completely controls the IC spark timing. The ICM, in any mode, is always responsible for proper ignition coil sequencing. In the IC mode, the PCM calculates IC spark timing based upon input signals from the following:

•	The engine speed (18X reference or 3X reference).

•	The crankshaft position (18X reference or 3X reference and camshaft position PCM input signal).

•	The engine coolant temperature (ECT sensor).

•	The throttle position (TP sensor).

•	The knock signals (knock sensors).

•	The park/neutral position (transaxle range switch or park/neutral position switch).

•	The vehicle speed (vehicle speed sensor / trans output speed sensor).

•	The PCM and the ignition system supply voltage (PCM ignition feed voltage).

Once the change is made to IC Mode, the change stays in effect until one of the following conditions occurs:

•	The engine is turned off.

•	The engine quits running.

If a PCM/IC fault (DTC P1351, P1352, P1361 and P1362) is detected while the engine is running, the engine may quit running. However the vehicle will restart, and may remain in Bypass Mode with a noticeable loss of performance.

Diagnosis

If the 18X reference signal is not received by the PCM while the engine is running, a DTC P0336 is set, the 3X reference is used to control spark advance under 1200 RPM, and Bypass Mode is in effect at engine speeds under 400 RPM. The engine continues to run and start normally.

If the 3X reference signal is not received by the PCM while the engine is running, the PCM uses the 18X reference pulses to calculate RPM and the crankshaft position. The engine continues to run and start normally, but DTC P1374 is set.

If an open reference low circuit occurs, reduced engine performance may result and possibly a MIL with no DTC.

The PCM generates IC timing pulses anytime crankshaft reference signals are being received. The PCM uses the IC control circuit to send the IC timing pulses to the ignition control module (ICM). When the ignition system is operating in the Bypass Mode (no voltage on the bypass control circuit), the ICM grounds the IC pulses. The ignition system switches to the IC Mode when the PCM applies the 5 volt bypass signal to the ICM on the bypass circuit. The ICM switches the IC pulses from ground in order to allow the PCM to control the spark timing. The PCM monitors the IC and bypass circuits for electrical malfunctions affecting proper ignition system operation. If a malfunction occurs, diagnosis is included in the DTC P1351, P1352, P1361, and P1362 diagnostic tables. If diagnostic trouble codes are encountered, go to the DTC tables for diagnosis.

The following information lists important considerations to aid the technician in servicing the ignition system.

•	The ignition coil's secondary voltage output capabilities are very high - more than 40,000 volts. Avoid body contact with the high voltage secondary ignition components when the engine is running, or personal injury may result.

•	The dual Hall-effect crankshaft position (CKP) sensor is the most critical part of the ignition system. If the sensor is damaged so that the CKP 18X or CKP sync crank sensor pulses are not generated, the engine does not start.

•	There are 4 circuit wires connecting the dual CKP sensor to the ignition control module. If there is a problem with any of the 4 circuit wires, the engine does not start (no spark and no injector pulses). The circuits are described as follows:

-	The 10 to 12 volt sensor feed for the Hall effect switches from the ignition control module.

-	The 18X CKP pulse signal to the ignition control module.

-	The CKP sync pulse signal to the ignition control module.

-	The sensor ground circuit for both Hall-effect switches.

•	If the CKP sync pulses stop while the engine is running, the engine keeps running. The ignition control module remembers the correct ignition coil sequence. However, the engine does not restart after being shut off.

•	If the 18X CKP pulses stop while the engine is running, the engine stops running and does not restart. The loss of the 18X CKP signal to the ICM results in the loss of CKP information and the ICM's ability to generate the 3X reference signals.

•	The CKP sensor clearance is very important. The sensor MUST NOT contact the rotating interrupter rings at any time, or sensor damage results. If the balancer interrupter rings are bent, the interrupter ring blades can destroy the sensor.

•	The ignition timing is not adjustable. There are no timing marks on the crankshaft balancer or timing chain cover.

•	If CKP sensor replacement is necessary, the crankshaft balancer must be removed first. The balancer is a press fit onto the crankshaft. Removing the serpentine accessory drive belt and balancer attaching bolt allows Balancer removal with the J 38197-A balancer remover.

•	When reinstalling the crankshaft balancer, torque the balancer attachment bolt to the proper specifications. This is critical in order to prevent crankshaft damage and to ensure that the balancer stays attached to the crankshaft.

•	If a CKP sensor assembly is replaced, inspect the crankshaft balancer interrupter rings for bent blades. If a bent blade exists, the new CKP sensor may be destroyed within a single crankshaft revolution.

•	Neither side of the ignition coil primary or secondary windings is connected to engine ground. Although the ignition coil packs are secured to the ignition control module, this is not an electrical connection to ground.

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Be careful not to damage the secondary ignition wires or boots when servicing the ignition system. Do not pull on the ignition wire(s) without rotating each boot to dislodge the boot from the plug or coil tower. NEVER pierce a secondary ignition wire or boot for any purpose. Future problems with the wire are certain if pinpoints or testlamps are pushed through the insulation for testing.

•	The ignition control module is grounded to the engine block through a ground wire to the bracket mounting stud of the ignition control module. If service is required, ensure that good electrical contact is made between the ground and the mounting bracket, including the proper hardware and torque.

•	A conventional tachometer used to measure RPM on a primary ignition tach lead does not work on this ignition system. To measure RPM, use either of the following items:

A tachometer designed with an inductive pickup, used on the secondary side of an ignition system. These tachometers are identified by a clamp that goes around a spark plug wire. Set the tachometer to 2-cycle operation. The 2-cycle setting is required because spark plugs on this engine fire every time the piston is at the top of a stroke. If a 2 cycle selection is not available, divide the indicated 4 cycle reading by 2.

-	A scan tool.