Engine Control System - 4.6L (LH2) - Introduction: Other Cadillac STS I

Temperature vs Resistance

Temperature vs Resistance

Altitude vs Barometric Pressure

Altitude vs Barometric Pressure

CKP System Variation Learn Procedure

1. Install a scan tool.
2. Monitor the engine control module (ECM) for DTCs with a scan tool. If other DTCs are set, except DTC P0315, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(ref-197532-S21291039732005101200000) in Vehicle DTC Information for the applicable DTC.
3. Select the crankshaft position variation learn procedure with a scan tool.
4. The scan tool instructs you to perform the following: Accelerate to wide open throttle (WOT). Release throttle when fuel cut-off occurs. Observe fuel cut-off for applicable engine. Engine should not accelerate beyond calibrated RPM value. Release throttle immediately if value is exceeded. Block drive wheels. Set parking brake. DO NOT apply brake pedal. Cycle ignition from OFF to ON. Apply and hold brake pedal. Start and idle engine. Turn A/C OFF. Vehicle must remain in Park or Neutral. The scan tool monitors certain component signals to determine if all the conditions are met to continue with the procedure. The scan tool only displays the condition that inhibits the procedure. The scan tool monitors the following components: Crankshaft position (CKP) sensors activity - If there is a CKP sensor condition, refer to the applicable DTC. Camshaft position (CMP) signal activity - If there is a CMP signal condition, refer to the applicable DTC. Engine coolant temperature (ECT) - If the engine coolant temperature is not warm enough, idle the engine until the engine coolant temperature reaches the correct temperature.
5. Enable the CKP system variation learn procedure with the scan tool and perform the following: IMPORTANT: While the learn procedure is in progress, release the throttle immediately when the engine starts to decelerate. The engine control is returned to the operator and the engine responds to throttle position after the learn procedure is complete. Accelerate to WOT. Release throttle when fuel cut-off occurs.
6. The scan tool displays Learn Status: Learned this ignition. If the scan tool indicates that DTC P0315 ran and passed, the CKP variation learn procedure is complete. If the scan tool indicates DTC P0315 failed or did not run, refer to «DTC P0315»(ref-197610-S14747517712005101200000) . If any other DTCs set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(ref-197532-S21291039732005101200000) in Vehicle DTC Information for the applicable DTC.
7. Turn OFF the ignition for 30 seconds after the learn procedure is completed successfully.

The CKP system variation learn procedure is also required when the following service procedures have been performed, regardless of whether or not DTC P0315 is set

1. An engine replacement
2. A ECM replacement
3. A harmonic balancer replacement
4. A crankshaft replacement
5. A CKP sensor replacement
6. Any engine repairs which disturb the crankshaft to CKP sensor relationship.

Throttle Body Service

1. Remove the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(ref-197575-S37763020362005101200000) in Engine Mechanical - 4.6L (LH2).
2. Remove the air cleaner outlet duct. Refer to «Air Cleaner Outlet Duct Replacement»(ref-197553-S04945234442005101200000) .
3. Inspect the throttle body bore and the throttle body plate for deposits. You will need to open the throttle plate in order to inspect all surfaces.
4. Clean the throttle body bore and the throttle plate using a clean shop towel with GM top engine cleaner, P/N 1052626 or AC Delco Carburetor Tune-up Conditioner, P/N X66P, or equivalent product.
5. Install the air cleaner outlet duct. Refer to «Air Cleaner Outlet Duct Replacement»(ref-197553-S04945234442005101200000) .
6. Install the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(ref-197575-S37763020362005101200000) in Engine Mechanical - 4.6L (LH2).

Tools Required

J 34730-1A Fuel Pressure Gage

1. Turn the ignition OFF.
2. Disconnect the negative battery cable in order to avoid possible fuel discharge if an accidental attempt is made to start the engine. Refer to «Battery Negative Cable Disconnect/Connect Procedure»(ref-197559-S16230888842005101200000) in Engine Electrical.
3. Remove the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(ref-197575-S37763020362005101200000) in Engine Mechanical - 4.6L (LH2).
4. Connect the J 34730-1A to the fuel pressure valve. Wrap a shop towel around the fitting while connecting the gage in order to avoid spillage.
5. Install the bleed hose into an approved container.
6. Open the valve in order to bleed the system pressure. Fuel connections are now safe for servicing.
7. Drain any fuel remaining in the gage into an approved container.
8. Install the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(ref-197575-S37763020362005101200000) in Engine Mechanical - 4.6L (LH2).
9. Connect the negative battery cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure»(ref-197559-S16230888842005101200000) in Engine Electrical.

J 34730-1A Fuel Pressure Gage

Quick Connect Fitting(s) Service (Metal Collar)

Tools Required

1. J 37088-A Fuel Line Disconnect Tool Set
2. J 44581 Fuel Line Disconnect Tool. See «Special Tools»(ref-197553-S01702336812005101200000) .

1. J 36850 Transjel Lubricant
2. J 42960-2 Fuel Flapper Door Holder
3. J 45004 Fuel Drain Hose

1. Remove the fuel filler cap.
2. Install the J 42960-2 into the fuel fill pipe in order to hold the door open.
3. Insert the J 45004 into the fuel tank until the hose reaches the bottom of the fuel tank.
4. Use an air operated pump device in order to drain the fuel into an approved gasoline container. Up to 26 liters (7 gallons) of residual fuel may remain in the secondary side of the fuel tank.
5. Simultaneously twist and pull in order to remove the J 45004 from the fuel tank.

J 45747 Fuel Tank Sender Wrench

J 45747 Fuel Tank Sender Wrench

Fuel System Cleaning

The following procedure covers the disassembly and the inspection of the complete fuel supply system. If the fuel system is contaminated, the fuel system can be cleaned. You can usually determine the extent of the fuel system contamination during the disassembly.

1. Remove the in-line fuel filter. Refer to «Fuel Filter Replacement»(ref-197553-S37996048952005101200000) .
2. Inspect the fuel system for contamination of the in-line fuel filter. Replace the filter after cleaning the fuel lines if the filter is plugged or contaminated.
3. Remove the fuel module assemblies. Refer to «Fuel Tank Module Replacement - Primary»(ref-197553-S10238900012005101200000) and «Fuel Tank Module Replacement - Secondary»(ref-197553-S10238611572005101200000) .
4. Locate the tank in a suitable work area away from any heat, any flame, or any other source of ignition.
5. Perform the following procedures: Inspect the fuel sender strainer. Replace the primary fuel tank module if the strainer is contaminated. Inspect the secondary fuel tank module for debris. Clean the secondary fuel tank module if debris is found. CAUTION: Wear safety glasses when using compressed air, as flying dirt particles may cause eye injury. Use compressed air in order to apply air pressure to the transfer tube.
6. Flush the fuel tank with running hot water for at least five minutes. Pour the water out of the fuel sender assembly opening. Rock the tank in order to ensure that the removal of the water from the tank is complete.
7. Disconnect the fuel feed hose/pipe from the fuel rail. Refer to «Quick Connect Fitting(s) Service (Metal Collar)»(ref-197553-S17077957172005101200000) .
8. Use compressed air in order to apply air pressure to the fuel lines in the opposite direction from the normal fuel flow.
9. Remove the fuel injectors and fuel rail. Refer to «Fuel Injectors and Fuel Rail Replacement»(ref-197553-S35918917832005101200000) .
10. Clean and inspect the fuel injectors and fuel rail.

Accelerator Pedal Position (APP) Sensor

The accelerator pedal position (APP) sensor is made up of 2 sensors that are housed inside one assembly. The engine control module (ECM) supplies a separate 5-volt reference and the low reference circuit for each of the sensors. The 5-volt reference for APP sensor 1 is supplied from the same source in the ECM as the 5-volt reference for the mass air flow (MAF) sensor and the fuel tank pressure (FTP) sensor. The 5-volt reference voltage for all of the sensors is supplied on separate ECM terminals, but the terminals are connected internally to a voltage supply. The APP sensor 1 sends a signal from the sensor to the ECM indicating the accelerator pedal position. The ECM actuates the throttle plates based on this information.

Throttle Position Sensors

The throttle position (TP) sensors 1 and 2 are located within the throttle body assembly. The TP sensors share a common 5-volt reference circuit and a common low reference circuit. The 5-volt reference circuit is also shared with accelerator pedal position (APP) sensor 2. The 5-volt reference voltage is supplied on 2 separate engine control module (ECM) terminals, but the terminals are connected internally to the same voltage supply. Each TP sensor has an individual signal circuit, which provides the ECM with a signal voltage proportional to throttle the plate movement. When the throttle plate is in the closed position, the TP sensor 1 signal voltage is near the low reference and increases as the throttle plate is opened. TP sensor 2 signal voltage at closed throttle is near the 5-volt reference and decreases as the throttle plate is opened.

Engine Control Module

The engine control module (ECM) determines the driver's intent and then calculates the appropriate throttle response.

Fuel Tank

The fuel storage tank is made of high density polyethylene. The fuel storage tank is held in place by 2 metal straps that are attached to the underbody of the vehicle. The tank shape includes a sump in order to maintain a constant supply of fuel around the fuel pump strainer during low fuel conditions or during aggressive maneuvers.

The fuel tank also contains a fuel vapor vent valve with a roll-over protection. The vent valve also features a 2-phase vent calibration which increases the fuel vapor flow to the canister when the operating temperatures increase the tank pressure beyond an established threshold.

On-Board Refueling Vapor Recovery (ORVR) System

The on-board refueling vapor recovery (ORVR) system is an on-board vehicle system to recover fuel vapors during the vehicle refueling operation. The flow of liquid fuel down to the fuel tank filler neck provides a liquid seal. The purpose of ORVR is to prevent refueling vapor from exiting the fuel tank filler neck.

Fuel Tank Filler Pipe

In order to prevent refueling with leaded fuel, the fuel filler pipe has a built-in restrictor and a deflector. The opening in the restrictor will accept only the smaller unleaded gasoline fuel nozzle which must be fully inserted in order to bypass the deflector. The tank is vented during filling by an internal vent tube inside of the filler pipe.

Scheme 118

Note. Use a fuel tank filler pipe cap with the same features as the original when a replacement is necessary. Failure to use the correct fuel tank filler pipe cap can result in a serious malfunction of the fuel system.

The fuel tank filler pipe is equipped with a turn to vent screw on the type cap which incorporates a ratchet action in order to prevent over-tightening.

The turn to vent feature allows the fuel tank pressure relief prior to removal. Instructions for proper use are imprinted on the cap cover. A vacuum safety relief valve is incorporated into this cap.

Scheme 119

The modular fuel sender assembly mounts to the threaded opening of the plastic fuel tank with a multi-lipped seal and a threaded retainer (nut). The reservoir, containing the exterior inlet strainer, the electric fuel pump, and the pump strainer, maintains contact with the tank bottom. This design provides

1. Optimum fuel level in the integral fuel reservoir during all fuel tank levels and during driving conditions
2. An improved tank fuel level measuring accuracy
3. An improved coarse straining and added pump inlet filtering
4. More extensive internal fuel pump isolation for noiseless operation

The modular fuel sender assembly maintains an optimum fuel level in the reservoir (bucket). The fuel entering the reservoir is drawn in by the following components

1. The first stage of the fuel pump through the external strainer AND/OR
2. The secondary umbrella valve OR
3. The return fuel line, whenever the level of fuel is below the top of the reservoir

Fuel Pump

The electric fuel pump is a turbine pump which is located inside of the modular fuel sender. The electric fuel pump operation is controlled by the engine control module (ECM) through the fuel pump relay.

Fuel Sender Strainers

The strainers act as a coarse filter to perform the following functions

1. Filter contaminants
2. Separate water from fuel
3. Provide a wicking action that helps draw fuel into the fuel pump

Fuel stoppage at the strainer indicates that the fuel tank contains an abnormal amount of sediment or water. Therefore, the fuel tank will need to be removed and cleaned, and the filter strainer should be replaced.

Scheme 120

The fuel filter is located on the fuel feed pipe, between the fuel pump and the fuel rail. The electric fuel pump supplies fuel through the in-line fuel filter to the fuel injection system. The fuel pressure regulator keeps the fuel available to the fuel injectors at a regulated pressure. Unused fuel is returned from the fuel filter to the fuel tank by a separate fuel return pipe. The paper filter element (2) traps particles in the fuel that may damage the fuel injection system. The filter housing (1) is made to withstand maximum fuel system pressure, exposure to fuel additives, and changes in temperature. There is no service interval for fuel filter replacement. Replace a restricted fuel filter.

EVAP Lines and Hoses

The evaporative emission (EVAP) line extends from the fuel tank vent valve to the EVAP canister and into the engine compartment. The EVAP line is made of nylon and connects to the EVAP canister with a fuel resistant rubber hose and quick connect fittings.

Scheme 121

The fuel pressure regulator attaches to the fuel return pipe on the fuel sender assembly. The fuel pressure regulator is a diaphragm-operated relief valve. A software bias compensates the injector on-time because the fuel pressure regulator is not referenced to manifold vacuum. The injector pulse width varies with the signal from the mass air flow/intake air temperature (MAF/IAT) sensor.

With the engine running at idle, the system fuel pressure at the pressure test connection should be between 380-410 kPa (55-60 psi). With the system pressurized and the pump OFF, the pressure should stabilize and hold. If the pressure regulator supplies a fuel pressure which is too low or too high, a driveability condition will result.

Fuel Rail

The fuel rail consists of 3 parts

1. The pipe that carries fuel to each injector
2. The fuel pressure test port
3. Eight individual fuel injectors

The fuel rail is mounted on the intake manifold and distributes the fuel to each cylinder through the individual injectors.

Fuel Injectors

The fuel injector is a solenoid device that is controlled by the engine control module (ECM). When the ECM energizes the injector coil, a normally closed ball valve opens, allowing the fuel to flow past a director plate to the injector outlet. The director plate has holes that control the fuel flow, generating a dual conical spray pattern of finely atomized fuel at the injector outlet. The fuel from the outlet is directed at both of the intake valves, causing the fuel to become further vaporized before entering the combustion chamber.

The fuel injectors will cause various driveability conditions if the following conditions occur

1. If the injectors will not open
2. If the injectors are stuck open
3. If the injectors are leaking
4. If the injectors have a low coil resistance

Fuel Pump Relay

The fuel pump relay allows the engine control module (ECM) to energize the fuel pump. The ECM enables the fuel pump whenever the crankshaft position (CKP) sensor pulses are detected.

The function of the fuel and air control system is to manage the fuel and the air delivery to each cylinder, optimizing the performance and the driveability of the engine under all driving conditions. The fuel sender allows retrieval of fuel from the tank and also provides information on the fuel level. An electric fuel pump contained in the modular fuel sender pumps the fuel through the nylon lines and an in-line fuel filter to the fuel rail. The pump is designed to provide the fuel at a pressure above the regulated pressure which is needed by the injectors. The fuel is then distributed through the fuel rail to 6 injectors inside of the intake manifold. The fuel pressure is controlled by a pressure regulator that is mounted on the fuel rail. The fuel system in this vehicle is recirculating. This means that any excess fuel that is not injected into the cylinders is sent back to the fuel tank by a separate nylon line. This removes any air and any vapors from the fuel as well as keeping the fuel cool during hot weather operation. Each fuel injector is located directly above each cylinders 2 intake valves. The throttle body regulates the air flow from the air cleaner into the intake manifold, which then distributes this air to each cylinders 2 intake valves.

Unleaded fuel must be used with all of the gasoline engines for a proper emission control system operation. Using unleaded fuel will also minimize any spark plug fouling and extend the engine oil life. Leaded fuel can damage the emission control system, and use of leaded fuel can result in loss of emission warranty coverage.

Engine Fueling

The engine is fueled by 8 individual injectors, one for each cylinder, that are controlled by the engine control module (ECM). The ECM controls each injector by energizing the injector coil for a brief period once every other engine revolution. The length of this brief period, or pulse, is carefully calculated by the ECM to deliver the correct amount of fuel for proper driveability and emissions control. The period of time when the injector is energized is called the pulse width and is measured in milliseconds, thousandths of a second.

While the engine is running, the ECM is constantly monitoring the inputs and recalculating the appropriate pulse width for each injector. The pulse width calculation is based on the injector flow rate, mass of fuel the energized injector will pass per unit of time, the desired air/fuel ratio, and actual air mass in each cylinder and is adjusted for battery voltage, short term, and long term fuel trim (FT). The calculated pulse is timed to occur as each cylinders intake valves are closing to attain largest duration and most vaporization.

Fueling during a crank is slightly different than fueling during an engine run. As the engine begins to turn, a prime pulse may be injected to speed starting. As soon as the ECM can determine where in the firing order the engine is, the ECM begins pulsing the injectors. The pulse width during the crank is based on the coolant temperature and the engine load.

The fueling system has several automatic adjustments in order to compensate for the differences in the fuel system hardware, the driving conditions, the fuel used, and the vehicle aging. The basis for the fuel control is the pulse width calculation that is described above. Included in this calculation are an adjustment for the battery voltage, the short term FT, and the long term FT. The battery voltage adjustment is necessary since the changes in the voltage across the injector affect the injector flow rate.

Fuel Trim

The engine control module (ECM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. The ECM monitors the heated oxygen sensor (HO2S) signal voltage while fuel injectors based on this signal. The ideal fuel trim (FT) values are around 0 percent for both short term and long term FT. A positive FT value indicates the ECM is adding fuel in order to compensate for a lean condition by increasing the pulse width. A negative FT value indicates that the ECM is reducing the amount of fuel in order to compensate for a rich condition by decreasing the pulse width. A change made to the fuel delivery changes the short term and long term FT values. The short term FT values change rapidly in response to the HO2S signal voltage. These changes fine tune the engine fueling. The long term FT makes coarse adjustments to fueling in order to re-center and restore control to short term FT. A scan tool can be used to monitor the short term and long term FT values. A block of cells contain information arranged in combinations of engine RPM and load for a full range of vehicle operating conditions. The long term FT diagnostic is based on an average of cells currently being used. If the powertrain control module (PCM) detects an excessive lean or rich condition, the ECM will set a FT DTC.

Sequential Fuel Injection (SFI)

The engine control module (ECM) controls the fuel injectors based on information that the ECM receives from several information sensors. Each injector is fired individually in the engine firing order, which is called sequential fuel injection. This allows precise fuel metering to each cylinder and improves the driveability under all of the driving conditions.

The ECM has several operating modes for fuel control, depending on the information that has been received from the sensors.

Starting Mode

When the engine control module (ECM) detects reference pulses from the crankshaft position (CKP) sensor, the ECM will enable the fuel pump. The fuel pump runs and builds up pressure in the fuel system. The ECM then monitors the mass air flow (MAF), intake air temperature (IAT), engine coolant temperature (ECT), and the throttle position (TP) sensor signal in order to determine the required injector pulse width for starting.

Clear Flood Mode

If the engine is flooded with fuel during starting and will not start, the Clear Flood Mode can be manually selected. To select Clear Flood Mode, push the accelerator to wide open throttle (WOT). With this signal, the engine control module (ECM) will completely turn OFF the injectors and will maintain this stage as long as the ECM indicates a WOT condition with engine speed below 1,000 RPM.

Run Mode

The Run Mode has 2 conditions: Open Loop operation and Closed Loop operation. When the engine is first started and the engine speed is above 480 RPM, the system goes into an Open Loop operation. In an Open Loop operation, the engine control module (ECM) ignores the signals from the oxygen sensors and calculates the required injector pulse width based primarily on inputs from the mass air flow (MAF), intake air temperature (IAT), and engine coolant temperatures (ECT) sensors.

In a Closed Loop, the ECM adjusts the calculated injector pulse width for each bank of injectors based on the signals from each oxygen sensor.

Acceleration Mode

The engine control module (ECM) monitors the changes in the throttle position (TP) and the mass air flow (MAF) sensor signals in order to determine when the vehicle is being accelerated. The ECM will then increase the injector pulse width in order to provide more fuel for improved driveability.

Deceleration Mode

The engine control module (ECM) monitors changes in the throttle position (TP) and the mass air flow (MAF) sensor signals to determine when the vehicle is being decelerated. The ECM will then decrease injector pulse width or even shut OFF injectors for short periods to reduce exhaust emissions.

Battery Voltage Correction Mode

The engine control module (ECM) can compensate in order to maintain acceptable vehicle driveability when the ECM sees a low battery voltage condition. The ECM compensates by performing the following functions

1. Increasing the injector pulse width in order to maintain the proper amount of fuel being delivered
2. Increasing the idle speed to increase the generator output

Fuel Shut-Off Mode

The engine control module (ECM) has the ability to completely turn OFF all of the injectors or selectively turn OFF some of the injectors when certain conditions are met. These fuel shut-off modes allow the ECM to protect the engine from damage and also to improve the vehicles driveability.

The ECM will disable all of the 6 injectors under the following conditions

1. Ignition OFF - Prevents engine run-on
2. Ignition ON but no ignition reference signal-Prevents flooding or backfiring
3. A high engine speed - Above the red line
4. A high vehicle speed - Above the rated tire speed
5. The extended high speed closed throttle coastdown - Reduces the emissions and increases engine braking

The ECM will selectively disable the injectors under the following conditions

1. The torque management enabled - Transmission shifts or abusive maneuvers
2. The traction control enabled - In conjunction with the front brakes applying

Check Gas Cap Message

The powertrain control module (PCM) sends a class 2 message to the driver information center (DIC) illuminating the Check Gas Cap message when any of the following occur

1. A malfunction in the evaporative emission (EVAP) system and a large leak test fails
2. A malfunction in the EVAP system and a small leak test fails

EVAP System Components

The evaporative emission (EVAP) system consists of the following components

EVAP Canister

The canister is filled with carbon pellets used to absorb and store fuel vapors. Fuel vapor is stored in the canister until the control module determines that the vapor can be consumed in the normal combustion process.

EVAP Purge Solenoid Valve

The EVAP purge solenoid valve controls the flow of vapors from the EVAP system to the intake manifold. The purge solenoid valve opens when commanded ON by the control module. This normally closed valve is pulse width modulated (PWM) by the control module to precisely control the flow of fuel vapor to the engine. The valve will also be opened during some portions of the EVAP testing, allowing engine vacuum to enter the EVAP system.

EVAP Vent Solenoid Valve

The EVAP vent solenoid valve controls fresh airflow into the EVAP canister. The valve is normally open. The control module commands the valve ON, closing the valve during some EVAP tests, allowing the system to be tested for leaks.

Fuel Tank Pressure Sensor

The fuel tank pressure (FTP) sensor measures the difference between the pressure or vacuum in the fuel tank and outside air pressure. The control module provides a 5-volt reference and a ground to the FTP sensor. The FTP sensor provides a signal voltage back to the control module that can vary between 0.1-4.9 volts. A high FTP sensor voltage indicates a low fuel tank pressure or vacuum. A low FTP sensor voltage indicates a high fuel tank pressure.

EVAP Service Port

The EVAP service port is located in the EVAP purge pipe between the EVAP purge solenoid valve and the EVAP canister. The service port is identified by a green colored cap.

Crankshaft Position (CKP) Sensor

The crankshaft position (CKP) sensor is a hall-effect sensor. An integrated circuit (IC) magnetic sensing element inside the sensor is magnetically biased by a permanent magnet located within the sensor. The CKP sensor circuits consist of a 12-volt reference circuit, a low reference circuit, and a signal circuit. The CKP sensor produces a DC voltage of varying amplitude and frequency. The frequency depends on the velocity of the crankshaft and the DC output voltage depends on the crankshaft position and battery voltage. The CKP sensor works in conjunction with a 58-tooth reluctor wheel attached to the crankshaft. As each reluctor wheel tooth rotates past the CKP sensor, the resulting change in the magnetic field is used by the sensor electronics to produce a digital output pulse. The sensor returns a digital ON/OFF pulse 58 times per crankshaft revolution. The engine control module (ECM) processes the digital pulse to create a signature pattern that enables the ECM to determine the crankshaft position. The CMP sensor signal is used to determine the position of the valve train relative to the crankshaft position. The ECM can synchronize the ignition timing, the fuel injector timing, and the spark knock control based on the CKP sensor and CMP sensor inputs. The CKP sensor is also used to detect misfire.

Crankshaft Reluctor Wheel

The crankshaft reluctor wheel is part of the crankshaft. The reluctor wheel consists of 58 teeth and a reference gap. Each tooth on the reluctor wheel is spaced 6 degrees apart with a 12-degree space for the reference gap. The reference gap is used to determine the crankshaft position (CKP), while the other teeth provide cylinder location during a revolution.

Camshaft Position (CMP) Sensor

The camshaft position (CMP) sensor is a hall ignition control (IC) type sensor. The sensor is true power on (TPO) at power up, which means it is capable of recognizing whether it is in front of a tooth or a notch at power up, and to set its output accordingly. The sensor is a high technology product that integrates a self calibrating system that compensates for environmental changes, such as temperature and air gap. The sensor is composed of a magneto-electronic module that generates a magnetic signal and transforms it into a digital signal. The sensor operates in 2 functional modes. The first mode is the static functional mode. This mode is valid at sensor power up. In this mode, the sensor behaves like a simple DC hall IC switch with 2 fixed switching points. The static functional mode is active during the first 10 mechanical edges of the reluctor wheel and as long as the signal frequency is lower than 1.2 Hertz, plus or minus 0.5 Hertz, with the one tooth reluctor wheel. When the signal frequency exceeds the previous mentioned limit, the sensor switches to the second functional mode, the self-calibrating functional mode. This mode enables the sensor to reach high angular position accuracy, which is not possible to achieve in the static functional mode. In the self-calibrating mode, the sensor acts as a field induction sensor, which is more accurate at higher engine RPM. The sensor switches from self-calibrating mode to static functional mode when the signal frequency becomes lower than 0.3 Hertz, plus or minus 0.1 Hertz, with the 1-tooth reluctor wheel. When the sensor switches back from self-calibrating mode to the TPO mode, a pulse of short duration is generated on the sensor output signal. The pulse may occur on the low signal state or on the high signal state.

The CMP sensor wiring consists of a 12-volt reference circuit, a low reference circuit, and a signal circuit. The CMP sensors work in conjunction with a 1-tooth reluctor wheel on the exhaust CMP actuators. The CMP sensors work in conjunction with an 8-tooth reluctor wheel on the intake CMP actuators. As each tooth on the reluctor wheel passes the CMP sensor it sends a digital signal, which is an image of the wheel, to the engine control module (ECM). The ECM processes this information to determine the exact position of the camshafts, and to determine the optimum ignition and injection points of the engine.

Camshaft Reluctor Wheels

The camshaft reluctor wheel is part of the camshaft position (CMP) actuator. This system consists of 2 different reluctor wheels. One for the exhaust camshafts on bank 1 and bank 2 and one for the intake camshafts on bank 1 and bank 2. The reluctor wheel on the exhaust CMP actuators has one tooth that extends 175 degrees around the circumference of the wheel. The reluctor wheel on the intake CMP actuators is an 8-tooth wheel that consists of 4 long and 4 short high and low phases. The 8X reluctor wheel is also used for the limp home mode.

Ignition Coil/Module

Each ignition coil/module has the following circuits

1. An ignition voltage circuit
2. A ground
3. An ignition control (IC) circuit
4. A low reference circuit

The engine control module (ECM) controls the individual coils by transmitting timing pulses on the IC circuit of each ignition coil/module to enable a spark event.

The spark plugs are connected to each coil by a short boot. The boot contains a spring that conducts the spark energy from the coil to the spark plug. The spark plug electrode is tipped with platinum for long wear and higher efficiency.

Knock Sensor

The knock sensor (KS) enables the control module to control the ignition timing for the best possible performance while protecting the engine from potentially damaging levels of detonation. The control module uses the KS system to test for abnormal engine noise that may indicate detonation, also known as spark knock.

This KS system uses one or 2 flat response 2-wire sensors. The sensor uses piezo-electric crystal technology that produces an AC voltage signal of varying amplitude and frequency based on the engine vibration or noise level. The amplitude and frequency are dependant upon the level of knock that the KS detects. The control module receives KS signal through a signal circuit. The KS ground is supplied by the control module through a low reference circuit.

The control module learns a minimum noise level, or background noise, at idle from the KS and uses calibrated values for the rest of the RPM range. The control module uses the minimum noise level to calculate a noise channel. A normal KS signal will ride within the noise channel. As engine speed and load change, the noise channel upper and lower parameters will change to accommodate the normal KS signal, keeping the signal within the channel. In order to determine which cylinders are knocking, the control module only uses KS signal information when each cylinder is near top dead center (TDC) of the firing stroke. If knock is present, the signal will range outside of the noise channel.

If the control module has determined that knock is present, it will retard the ignition timing to attempt to eliminate the knock. The control module will always try to work back to a zero compensation level, or no spark retard. An abnormal KS signal will stay outside of the noise channel or will not be present. KS diagnostics are calibrated to detect faults with the KS circuitry inside the control module, the KS wiring, or the KS voltage output. Some diagnostics are also calibrated to detect constant noise from an outside influence such as a loose/damaged component or excessive engine mechanical noise.

Engine Control Module (ECM)

The engine control module (ECM) controls all ignition system functions, and constantly corrects the basic spark timing. The ECM monitors information from various sensor inputs that include the following

1. The throttle position (TP) sensor
2. The engine coolant temperature (ECT) sensor
3. The mass air flow (MAF) sensor
4. The intake air temperature (IAT) sensor
5. The vehicle speed sensor (VSS)
6. The transmission gear position or range information sensors
7. The engine knock sensor (KS)

Purpose

The knock sensor (KS) system enables the control module to control the ignition timing for the best possible performance while protecting the engine from potentially damaging levels of detonation. The control module uses the KS system to test for abnormal engine noise that may indicate detonation, also known as spark knock.