DESCRIPTION
The Computer Controlled Coil Ignition (C(3)I) system, used on 3.3L and 3.8L engines, eliminates the need for a mechanical distributor. The C(3)I system consists of a coil pack, ignition module, camshaft (3.8L) and/or combination sensor, wiring harness, and the Electronic Spark Timing (EST) portion of the Electronic Control Module (ECM). Ignition timing is controlled by the ECM based upon inputs signals from the, camshaft position sensor (3.8L), engine RPM reference line, coolant temperature sensor, manifold air temperature sensor, throttle position sensor, knock sensor, vehicle speed sensor, gear position switch, and the mass airflow sensor.
In the C(3)I system, each cylinder is paired with the cylinder that is opposite it in the firing order. Cylinders No. 1-4, 5-2, and 3-6 are paired. Spark occurs simultaneously in the cylinder coming up on the compression stroke and in the cylinder coming up on the exhaust stroke. The cylinder on the exhaust stroke requires less voltage for the spark plug to fire. This leaves the bulk of the available voltage to fire the spark plug for the cylinder on the compression stroke. The process is repeated when the cylinders reverse roles. Each cylinder pair is fired by its own ignition coil.
IGNITION MODULE
The ignition module monitors input signals from several engine sensors. Input from the combination sensor is used by the ignition module to determine when to trigger the No. 1/4 coil pack. On 3.8L models, module passes this signal on to the ECM so that sequential fuel injector timing can be initialized.
At engine speeds less than 400 RPM, the ignition module controls spark advance by triggering each of the 3 coils at a predetermined interval based on engine speed only. At engine speeds greater than 400 RPM (EST mode), the ECM compensates for all driving conditions. On 3.8L engines, when in EST mode, ECM also changes fuel injection timing to a sequential mode. The ignition module is located directly below the ignition coil pack.
ELECTRONIC SPARK TIMING (EST)
The EST system uses the same ignition module-to-ECM circuits that distributor type ignition systems use, with the addition of fuel control and fuel sync (camshaft) signals on 3.8L engines. Operation of each circuit is described in the following paragraphs.
RPM Reference Signal
The reference signal provides the ECM with RPM and crankshaft position information from the C(3)I ignition module. A loss of RPM reference signal will prevent engine from running. In order for the ignition module to trigger the No. 1 coil pack, ignition module must first see a TDC No. 1 signal, followed by an RPM signal (18X signal on 3.8L).
Note. A conventional tachometer used to check RPM on a primary ignition tach lead will not work on the C(3)I system due to the fact that the coil triggers each time the piston is at TDC (both compression and exhaust). To obtain proper RPM readings, use a "Scan" tester connected to the ALDL connector, or use an inductive tachometer on the 2-cycle scale. If a 2-cycle scale is unavailable, divide 4-cycle reading by 2.
By-Pass Signal
At about 400 RPM, the ECM applies 5 volts to this circuit to switch spark timing control from the C(3)I module to the ECM. An open or grounded by-pass circuit will operate engine in a back-up ignition timing mode. Code 42 (E042 on some models) will be set.
EST Signal
The C(3)I module sends a reference signal to the ECM when the engine is cranking. If the engine speed is under 400 RPM, the ignition module controls the ignition timing. When engine speed exceeds 400 RPM, ECM applies 5 volts to the by-pass line to switch spark timing to ECM control on the EST line. An open or grounded EST circuit will stall the engine. The engine can be restarted but will stall again when the by-pass signals activates the EST line. Code 42 (EO42 on some models) will be set.
Reference Ground
A separate ground wire is used on this system to ensure there is no voltage drop which might affect ignition operation. Loss of ignition ground may cause intermittent ignition operation, incorrect RPM reference signals to ECM, or a false Code 42 (EO42 on some models).
ELECTRONIC SPARK CONTROL (ESC)
The ESC system consists of a knock (detonation) sensor and the MEM-CAL portion of the ECM. The ECM supplies and monitors a 5-volt DC reference signal on the knock sensor signal line. Internal circuitry of the knock sensor will pull this voltage down to about 2.5 volts. When knock occurs, the knock sensor produces an AC voltage signal which rides on the 2.5-volt DC signal. The voltage and frequency of this signal depend upon knock signals received by the sensor. The ECM will retard spark timing until signals from detonation sensor cease.
Type II (3.3L)
On type II ignition coils, 3 separate coils are independently mounted over the C(3)I ignition module. Each coil provides the spark for 2 simultaneously paired spark plugs. Each coil can be replaced separately.
Type III (3.8L)
On type III ignition coils, 3 twin tower coils are combined into a single coil pack. Coil pack is mounted directly over the C(3)I ignition module. Each coil provides the spark for 2 simultaneously paired spark plugs. All 3 coils must be replaced as a unit. Although old-style type I coil pack will physically fit on ignition module, the No. 1/4 coil pack is in a different location in relation to module connector.
Scheme 12
COMBINATION SENSOR (3.3L)
The combination cam/crank sensor actually consists of 2 Hall Effect sensors mounted, in a single unit, near the harmonic balancer. Since the 3.3L engine uses a double-fire simultaneous injection system rather than a sequential fuel injection system, it does not require a distinctive (TDC No. 1 piston compression) camshaft signal. Instead, each engine revolution, camshaft portion of the combination sensor generates a TDC signal for the No. 1/4 cylinder pair. Each engine revolution, the second sensor (crankshaft) generates RPM information and signals for the 1/4, 2/5 and 3/6 cylinder pairs.
CAMSHAFT POSITION SENSOR (3.8L)
The 3.8L camshaft sensor is located on the timing cover, behind and below water pump. (Scheme 13) The ECM uses camshaft signals to determine the exact position of the No. 1 piston. This signal represents the No. 1 piston on its compression stroke. Signal is used by ECM to properly initialize fuel injector firing. If camshaft sensor signal is lost, Code 41 (E041 on some models) will be set. The engine can be restarted and will run in sequential mode, however, without the camshaft signal, there is a 1 in 6 chance of injectors spraying correctly. This provides walk home protection against cam sensor failure.
COMBINATION 3X & 18X SENSORS (3.8L)
In addition to the camshaft sensor, the 3.8L engine contains sensors which are similar to the combination sensor used on the 3.3L engine; however, the interrupter rings on the back side of the balancer differ in configuration and purpose. The outside ring contains 18 evenly spaced interrupters, producing 18 pulses per crankshaft revolution. The inner ring has 3 interrupters spaced at irregular intervals (10 degrees, 20 degrees and 30 degrees apart).
The ignition module monitors signals generated by the 2 interrupter rings. The 18X ring will change state once during the 10 degree gap of the 3X ring, twice during the 20 degree gap, and three times during the 30 degree gap. The changing relationship between the 2 rings allows the ignition module to identify the correct ignition coil to fire within the first 120 degrees of crankshaft rotation. This system provides for a faster start and a more accurate measurement of the crankshaft sensor signals.
If the 3X signal to ignition module is lost while the engine is running, the fuel injection system will continue to run in sequential mode; however, loss of the 3X, or the 18X signal, will not allow the vehicle to restart.
Scheme 13
FUEL CONTROL SIGNAL (3.8L)
In addition to the RPM reference (18X) signal and fuel sync (camshaft) signals generated by the ignition module on 3.8L models, a fuel control reference signal must also be passed on to the ECM in order to inform ECM that proper signals are being generated to the ignition module. The fuel control signal is generated by the C(3)I module from calculations involving signals from the 18X and the 3X pulse rings.
ADJUSTMENTS
Other than spark plug gap, there are no adjustments possible on the C(3)I system; however, in order to maintain proper interrupter ring-to-sensor clearances, special installation procedures must be followed. See REMOVAL & INSTALLATION in this article.
TROUBLE SHOOTING
Note. See the TROUBLE SHOOTING - BASIC PROCEDURES article in the GENERAL TROUBLE SHOOTING section.
TESTING & DIAGNOSIS
The C(3)I and ESC systems are an integral part of the engine's computerized engine control system. See appropriate General Motors component chart C-4 or C-5 in the appropriate TESTS W/CODES article in the ENGINE PERFORMANCE section for testing and diagnosis information. Refer tothe following list. If engine cranks but will not run or if it stalls, appropriate CHART A-3 must be used to determine if failure is in the C(3)I ignition system or fuel injection system. If either Code 41 or Code 42 (E041 or E042 on some models) is set, use appropriate trouble code chart for proper diagnosis.
- For 2.0L VIN [K], see: «2.0L(K)/2.5L TESTS W/CODES»(/buick/skylark/vi-1986-1992/remont/testing-diagnostics/#20lk25l-tests-wcodes)
- For 2.0L VIN [1], see: «2.0L VIN [1] TESTS W/CODES»(ref-94905)
- For 2.0L Turbo, see: «2.0L TURBO TESTS W/CODES»(ref-94910)
- For 2.5L, see: «2.0L(K)/2.5L TESTS W/CODES»(/buick/skylark/vi-1986-1992/remont/testing-diagnostics/#20lk25l-tests-wcodes)
- For Cutlass Ciera & Cutlass Cruiser 2.8L, see: «2.8L VIN [W] PFI TESTS W/CODES»(ref-94907)
- For 3.1L, see: «3.1L VIN [T] PFI TESTS W/CODES»(ref-58099)
- For 3.3L, see: «3.3L/3.8L PFI TESTS W/CODES»(/buick/skylark/vi-1986-1992/remont/testing-diagnostics/#33l38l-pfi-tests-wcodes)
- For 3.8L, see: «3.3L/3.8L PFI TESTS W/CODES»(/buick/skylark/vi-1986-1992/remont/testing-diagnostics/#33l38l-pfi-tests-wcodes)
Removal & Installation
Disconnect negative battery cable. Unplug 14-way connector at ignition module. Disconnect spark plug wires from coil pack. Remove 3 nuts and washers securing ignition module to bracket. Remove 6 coil-to-ignition module Torx screws. Note wire colors for reassembly. Unplug connectors between ignition coil and module. Remove module. To install, reverse removal procedure. Tighten Torx screws to 27 INCH lbs. (3 N.m).
Removal
- Disconnect serpentine belt from crankshaft pulley. Raise vehicle on hoist. Remove right front tire and wheel assembly. Remove right side lower engine compartment filler panel and right lower wheelwell-to-engine compartment bolt, if necessary.
- Using 28 mm socket, remove crankshaft harmonic balancer retaining bolt. Remove harmonic balancer. Disconnect sensor harness connector. Remove sensor and pedestal (as an assembly) from block.
Installation
- Loosen pinch bolt until sensor is free to slide in pedestal. Position sensor, with pedestal attached, onto Installer (J-37089). Position installer onto crankshaft. (Scheme 14)
- Install pedestal-to-block bolts. Tighten bolts to 14-28 ft. lbs. (20-40 N.m). Tighten pedestal pinch bolt to 30-35 INCH lbs. (3-4 N.m). Remove installer.
- Place harmonic balancer onto installer. Rotate balancer on installer. If any vanes of interrupter rings contact installer, replace harmonic balancer.
- Install balancer on crankshaft. Tighten balancer retaining bolt to 200-239 ft. lbs. (270-325 N.m). To complete installation, reverse removal procedure.
Scheme 14
Removal & Installation (3.8L)
Disconnect negative battery cable. Remove camshaft sensor attaching bolt. Disconnect wiring harness and remove sensor. To install, reverse removal procedure.
Disconnect negative battery cable. Remove spark plug wires from coil. Remove 2 bolts securing coil to module. Remove coil assembly. To install, reverse removal procedure. Tighten retaining bolts to 27 INCH lbs. (3 N.m).
Disconnect negative battery cable. Remove spark plug wires from coil pack. Remove 6 Torx screws securing coil to ignition module. Tilt coil assembly back. Disconnect module connectors and remove coil pack. To install, reverse removal procedure. Tighten retaining bolts to 27 INCH lbs. (3 N.m).
OVERHAUL
Overhaul information is not available.
TORQUE SPECIFICATIONS
| Application | Ft. Lbs (N.m) |
|---|---|
| Combination Sensor Pedestal-to-Block Bolts | 14-28 (20-40) |
| Crankshaft Balancer | 200-239 (270-325) |
| INCH Lbs (N.m) | |
| Combination Sensor Pedestal Pinch Bolt | 30-35 (3-4 N) |
| Ignition Coil Mounting Bolts | 27 (3) |
| Ignition Module Torx Screws | 27 (3) |
TORQUE SPECIFICATIONS
WIRING DIAGRAMS
For C(3)I wiring diagrams, refer to appropriate General Motors component CHART C-4 or CODE 42 in appropriate TESTS W/CODES article in the ENGINE PERFORMANCE section. See the following list.
- For 2.0L VIN [K], see: «2.0L(K)/2.5L TESTS W/CODES»(/buick/skylark/vi-1986-1992/remont/testing-diagnostics/#20lk25l-tests-wcodes)
- For 2.0L VIN [1], see: «2.0L VIN [1] TESTS W/CODES»(ref-94905)
- For 2.0L Turbo, see: «2.0L TURBO TESTS W/CODES»(ref-94910)
- For 2.5L, see: «2.0L(K)/2.5L TESTS W/CODES»(/buick/skylark/vi-1986-1992/remont/testing-diagnostics/#20lk25l-tests-wcodes)
- For Cutlass Ciera & Cutlass Cruiser 2.8L, see: «2.8L VIN [W] PFI TESTS W/CODES»(ref-94907)
- For 3.1L, see: «3.1L VIN [T] PFI TESTS W/CODES»(ref-58099)
- For 3.3L, see: «3.3L/3.8L PFI TESTS W/CODES»(/buick/skylark/vi-1986-1992/remont/testing-diagnostics/#33l38l-pfi-tests-wcodes)
- For 3.8L, see: «3.3L/3.8L PFI TESTS W/CODES»(/buick/skylark/vi-1986-1992/remont/testing-diagnostics/#33l38l-pfi-tests-wcodes)