Engine Control System - 4.2L - Introduction: Other GMC Envoy II

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 powertrain control module (PCM) for DTCs with a scan tool. If other DTCs are set, except DTC P0315, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(ref-200355-S26002694682005102000000) in Vehicle DTC Information.
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 the 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) sensor activity - If a CKP sensor condition occurs, refer to the applicable DTC. Camshaft position (CMP) signal activity - If a CMP signal condition occurs, 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: Accelerate to WOT Release the throttle when fuel cut-off occurs Test in progress
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-200427-S35234659642005102000000) . If any other DTCs set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(ref-200355-S26002694682005102000000) in Vehicle DTC Information.
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 PCM replacement
3. A crankshaft balancer replacement
4. A crankshaft replacement
5. A CKP sensor replacement
6. Any engine repairs which disturb the crankshaft to CKP sensor relationship

Tools Required

J 39194-B Heated Oxygen Sensor Wrench. See Special Tools & Equipment .

J 39194-B Heated Oxygen Sensor Wrench. See Special Tools & Equipment .

Fuel Pressure Relief Procedure

1. Remove the fuel pump relay (1) from the junction box (2).
2. Crank the engine.
3. Allow the engine to start and stall.
4. Crank the engine for an additional 3 seconds to ensure the relief of any remaining fuel pressure.
5. Disconnect the negative battery cable in order to avoid re-pressurizing the fuel system. Refer to «Battery Negative Cable Disconnect/Connect Procedure»(ref-200375-S07741338702005102000000) in Engine Electrical.
6. Install the fuel pump relay (1) to the junction box (2).
7. Tighten the fuel filler cap.

J 34730-1A Fuel Pressure Gage. See Special Tools & Equipment .

Tool Required

J 37088-A Fuel Line Disconnect Tool Set. See Special Tools & Equipment .

J 44402 Fuel Tank Sending Unit Wrench. See Special Tools & Equipment .

Fuel System Cleaning

1. Remove the fuel sender assembly. Refer to «Fuel Sender Assembly Replacement»(ref-200372-S24643162872005102000000) .
2. Inspect the fuel pump inlet for dirt and debris. Replace the fuel pump if you find dirt or debris in the fuel pump inlet.
3. Flush the fuel tank with hot water.
4. Pour the water out of the fuel sender assembly opening. Rock the tank to be sure that removal of the water from the tank is complete.
5. Install the fuel sender assembly. Refer to «Fuel Sender Assembly Replacement»(ref-200372-S24643162872005102000000) .

Fuel Injector Cleaning Procedure

Tools Required

1. J 37287 Fuel Line Shut-Off Adapters. See «Special Tools & Equipment»(ref-200372-S36410128202005102000000) .
2. J 35800-A Fuel Injector Cleaner
3. J 42873-1 3/8 Fuel Line Shut-Off Valve. See «Special Tools & Equipment»(ref-200372-S36410128202005102000000) .
4. J 42873-2 5/16 Return Pipe Shut-Off Valve. See «Special Tools & Equipment»(ref-200372-S36410128202005102000000) .
5. J 42964-1 3/8 Fuel Pipe Shut-Off Valve. See «Special Tools & Equipment»(ref-200372-S36410128202005102000000) .
6. J 42964-2 5/16 Fuel Pipe Shut-Off Valve. See «Special Tools & Equipment»(ref-200372-S36410128202005102000000) .

Note. GM Top Engine Cleaner is the only injector cleaning agent recommended. Do not use other cleaning agents, as they may contain methanol which can damage fuel system components. Under NO circumstances should the top engine cleaner be added to the vehicles fuel tank, as it may damage the fuel pump and other system components. Do not exceed a 10 percent cleaning solution concentration. Higher concentrations may damage fuel system components. Testing has demonstrated that exceeding the 10 percent cleaning solution concentration does not improve the effectiveness of this procedure.

1. Obtain J 35800-A (2).
2. For US dealers, empty 2 pre-measured GM Top-Engine Cleaner containers, 24 ml (0.812 oz) each, GM P/N 12346535, into the J 35800-A .
3. For Canadian dealers, measure and dispense 48 ml (1.62 oz) of Top-Engine Cleaner, Canadian P/N 992872, into the J 35800-A .
4. If you are using any other brand of tank you will need a total of 96 ml (3.24 oz) of Top-Engine Cleaner mixed with 864 ml (29.16 oz) of regular unleaded gasoline.
5. Fill the injector cleaning tank with regular unleaded gasoline. Be sure to follow all additional instructions provided with the tool.
6. Electrically disable the vehicle fuel pump by removing the fuel pump relay and disconnecting the oil pressure switch connector, if equipped.
7. Disconnect the fuel feed and return line, if equipped, at the fuel rail. Plug the fuel feed and return line, if equipped, coming off the fuel rail with J 37287 , or J 42964-1 , and J 42964-2 or J 42873-1 , and J 42873-2 as appropriate for the fuel system. See «Special Tools & Equipment»(ref-200372-S36410128202005102000000) .
8. Connect the J 35800-A to the vehicle fuel rail.
9. Pressurize the J 35800-A to 510 kPa (75 psi).
10. Start and idle the engine until it stalls due to lack of fuel. This should take approximately 15-20 minutes.
11. Disconnect J 35800-A from the fuel rail.
12. Reconnect the vehicle fuel pump relay and oil pressure switch connector, if equipped.
13. Remove J 37287 or J 42964-1 , and J 42964-2 or J 42873-1 , and J 42873-2 and reconnect the vehicle fuel feed and return lines. See «Special Tools & Equipment»(ref-200372-S36410128202005102000000) .
14. Start and idle the vehicle for an additional 2 minutes to ensure residual injector cleaner is flushed from the fuel rail and fuel lines.
15. Repeat steps 1-5 of the Injector Balance Test, and record the fuel pressure drop from each injector.
16. Subtract the lowest fuel pressure drop from the highest fuel pressure drop. If the value is 15 kPa (2 psi) or less, no additional action is required. If the value is greater than 15 kPa (2 psi), replace the injector with the lowest fuel pressure drop.
17. Add one ounce of Port Fuel Injector Cleaner, GM P/N 12345104 (Canadian P/N 10953467), to the vehicle fuel tank for each gallon of gasoline estimated to be in the fuel tank. Instruct the customer to add the reminder of the bottle of Port Fuel Injector Cleaner to the vehicle fuel tank at the next fill-up.
18. Advise the customer to change brands of fuel and to add GM Port Fuel Injector Cleaner every 5 000 km (3,000 mi). GM Port Fuel Injector Cleaner contains the same additives that the fuel companies are removing from the fuel to reduce costs. Regular use of GM Port Fuel Injector Cleaner should keep the customer from having to repeat the injector cleaning procedure.
19. Road test the vehicle to verify that the customer concern has been corrected.

J 41413 EVAP Pressure and Purge Station

EVAP Cleaning Procedure

1. Remove the EVAP canister. Refer to «Evaporative Emission (EVAP) Canister Replacement (TrailBlazer, Envoy, Rainier)»(ref-200372-S40072272842005102000000) or «Evaporative Emission (EVAP) Canister Replacement (Trailblazer EXT, Envoy XL, Envoy XUV)»(ref-200372-S10614409732005102000000) .
2. Turn OFF the main valve on the J 41413 .
3. Disconnect the hose from the diagnostic station pressure regulator.
4. Using a section of vacuum hose, connect one end to the diagnostic station pressure regulator.
5. Connect the other end of the vacuum hose to the canister side of the purge pipe.
6. Turn ON the main nitrogen cylinder valve and continue to discharge nitrogen for 15 seconds.
7. If the nitrogen does not dislodge the carbon particles, replace the purge pipe. Refer to «Evaporative Emission (EVAP) Hoses/Pipes Replacement - Engine/Chassis»(ref-200372-S03430970042005102000000) .
8. Return the J 41413 to its original condition.
9. Install a new EVAP canister. Refer to «Evaporative Emission (EVAP) Canister Replacement (TrailBlazer, Envoy, Rainier)»(ref-200372-S40072272842005102000000) or «Evaporative Emission (EVAP) Canister Replacement (Trailblazer EXT, Envoy XL, Envoy XUV)»(ref-200372-S10614409732005102000000) .
10. Install a new EVAP canister purge valve. Refer to «Evaporative Emission (EVAP) Canister Purge Solenoid Valve Replacement»(ref-200372-S18747729702005102000000) .
11. Lower the vehicle.
12. Continue with the published service manual diagnostic trouble code (DTC) procedure.

Spark Plug Usage

1. Ensure that the correct spark plug is installed. An incorrect spark plug causes driveability conditions. Refer to «Ignition System Specifications»(ref-200372-S24765872602005102000000) for the correct spark plug.
2. Ensure that the spark plug has the correct heat range. An incorrect heat range causes the following conditions: Spark plug fouling-Colder plug Pre-ignition causing spark plug and/or engine damage-Hotter plug

Powertrain

The powertrain has electronic controls to reduce exhaust emissions while maintaining excellent driveability and fuel economy. The powertrain control module (PCM) is the control center of this system. The PCM monitors numerous engine and vehicle functions. The PCM constantly looks at the information from various sensors and other inputs, and controls the systems that affect vehicle performance and emissions. The PCM also performs the diagnostic tests on various parts of the system. The PCM can recognize operational problems and alert the driver via the malfunction indicator lamp (MIL). When the PCM detects a malfunction, the PCM stores a diagnostic trouble code (DTC). The problem area is identified by the particular DTC that is set. The control module supplies a buffered voltage to various sensors and switches. Review the components and wiring diagrams in order to determine which systems are controlled by the PCM.

The following are some of the functions that the PCM controls

1. The engine fueling
2. The ignition control (IC)
3. The knock sensor (KS) system
4. The evaporative emissions (EVAP) system
5. The secondary air injection (AIR) system (if equipped)
6. The exhaust gas recirculation (EGR) system
7. The automatic transmission functions
8. The generator
9. The A/C clutch control
10. The cooling fan control

Powertrain Control Module Function

The powertrain control module (PCM) constantly looks at the information from various sensors and other inputs and controls systems that affect vehicle performance and emissions. The PCM also performs diagnostic tests on various parts of the system. The PCM can recognize operational problems and alert the driver via the malfunction indicator lamp (MIL). When the PCM detects a malfunction, the PCM stores a diagnostic trouble code (DTC). The problem area is identified by the particular DTC that is set. The control module supplies a buffered voltage to various sensors and switches. The input and output devices in the PCM include analog-to-digital converters, signal buffers, counters, and output drivers. The output drivers are electronic switches that complete a ground or voltage circuit when turned on. Most PCM controlled components are operated via output drivers. The PCM monitors these driver circuits for proper operation and, in most cases, can set a DTC corresponding to the controlled device if a problem is detected.

Trip

A trip is an interval of time during which the diagnostic test runs. A trip may consist of only a key cycle to power up the powertrain control module (PCM), allow the diagnostic to run, then cycle the key off to power down the PCM. A trip may also involve a PCM power up, meeting specific conditions to run the diagnostic test, then powering down the PCM. The definition of a trip depends upon the diagnostic. Some diagnostic tests run only once per trip (i.e., catalyst monitor) while other tests run continuously during each trip (i.e., misfire).

Warm-Up Cycle

The powertrain control module (PCM) uses warm-up cycles to run some diagnostics and to clear any diagnostic trouble codes (DTCs). A warm-up cycle occurs when the engine coolant temperature increases 22°C (40°F) from the start-up temperature. The engine coolant must also achieve a minimum temperature of 71°C (160°F). The PCM counts the number of warm-up cycles in order to clear the malfunction indicator lamp (MIL). The PCM will clear the DTCs when 40 consecutive warm-up cycles occur without a malfunction.

Accelerator Pedal Position (APP) Sensor

The APP sensor is mounted on the accelerator pedal assembly. The APP is actually 2 individual APP sensors within 1 housing. There are 2 separate signal, low reference, and 5-volt reference circuits. APP sensor 1 voltage increases as the accelerator pedal is depressed. APP sensor 2 voltage decreases as the accelerator pedal is depressed.

Battery Saver Mode

If the powertrain control module (PCM) detects the ignition ON for 10 seconds without the engine running, the PCM will allow the throttle blade to return to the default position. This removes the draw that is present while holding the throttle blade at the calculated idle position.

Reduced Engine Power Mode

When the PCM detects a problem with the TAC system the PCM enters one of the following Reduced Engine Power Modes

1. Acceleration Limiting-The control module will continue to use the accelerator pedal for throttle control, however the vehicle acceleration is limited.
2. Limited Throttle Mode-The control module will continue to use the accelerator pedal for throttle control, however the maximum throttle opening is limited.
3. Throttle Default Mode-The control module will turn off the throttle actuator.
4. Forced Idle Mode-The control module will perform the following actions: Limit engine speed to idle by positioning throttle position, or by controlling fuel and spark if throttle is turned off. Ignore accelerator pedal input.
5. Engine Shutdown Mode-The control module will disable fuel and de-energize the throttle actuator.

Camshaft Position (CMP) Actuator System

The Camshaft Position Actuator system is used for a variety of engine performance enhancements. These enhancements include lower emission output through exhaust gas recirculation control, a wider engine torque range, improved gas millage, and improved engine idle stability. The CMP Actuator system accomplishes this by controlling the amount of intake and exhaust valve overlap.

Fuel Tank

The fuel tank stores the fuel supply. The fuel tank is located on the left side of the vehicle. The fuel tank is held in place by 2 metal straps that attach to the frame. The fuel tank is molded from high-density polyethylene.

Fuel Fill Pipe

The fuel fill pipe has a built-in restrictor in order to prevent refueling with leaded fuel.

Fuel Filler Cap

Note. If a fuel tank filler cap requires replacement, use only a fuel tank filler cap with the same features. Failure to use the correct fuel tank filler cap can result in a serious malfunction of the fuel and EVAP system.

The fuel fill pipe has a tethered fuel filler cap. A torque-limiting device prevents the cap from being over-tightened. To install the cap, turn the cap clockwise until you hear audible clicks. This indicates that the cap is correctly torqued and fully seated. A fuel filler cap that is not fully seated may cause a malfunction in the emission system.

Fuel Pump

The fuel pump is mounted in the fuel sender assembly reservoir. The fuel pump is an electric high-pressure pump. Fuel is pumped to the fuel injection system at a specified flow and pressure. The fuel pump delivers a constant flow of fuel to the engine even during low fuel conditions and aggressive vehicle maneuvers. The control module controls the electric fuel pump operation through a fuel pump relay. The fuel pump flex pipe acts to dampen the fuel pulses and noise generated by the fuel pump.

Fuel Filter

The fuel filter is contained in the fuel sender assembly inside the fuel tank. The paper filter element traps particles in the fuel that may damage the fuel injection system. The filter housing is made to withstand maximum fuel system pressure, exposure to fuel additives, and changes in temperature.

Scheme 62

The fuel pressure regulator (2) is contained in the fuel sender assembly. The fuel pressure regulator is a diaphragm relief valve. The diaphragm has fuel pressure on one side and regulator spring pressure on the other side. The fuel pressure regulator is not vacuum biased. Fuel pressure is controlled by a pressure balance across the regulator. The fuel system pressure is constant.

Fuel Feed Pipes

The fuel feed pipe carries fuel from the fuel tank to the fuel injection system. The fuel feed pipe consists of 2 sections

1. The rear fuel pipe is located from the top of the fuel tank to the chassis fuel pipe. The rear fuel pipe is constructed of nylon.
2. The chassis fuel pipe is located under the vehicle and connects the rear fuel pipe to the fuel injection system. The chassis fuel pipe is constructed of nylon and steel.

Nylon Fuel Pipes

Nylon pipes are constructed to withstand maximum fuel system pressure, exposure to fuel additives, and changes in temperature. There are 2 sizes of nylon pipes used

1. 9.53 mm (3/8 in) ID for the fuel feed
2. 12.7 mm (1/2 in) ID for the vent

Heat resistant rubber hose or corrugated plastic conduit protect the sections of the pipes that are exposed to chafing, high temperature, or vibration.

Nylon fuel pipes are somewhat flexible and can be formed around gradual turns under the vehicle. However, if nylon fuel pipes are forced into sharp bends, the pipes kink and restrict the fuel flow. Also, once exposed to fuel, nylon pipes may become stiffer and are more likely to kink if bent too far. Take special care when working on a vehicle with nylon fuel pipes.

Quick-Connect Fittings

Quick-connect fittings provide a simplified means of installing and connecting fuel system components. The fittings consist of a unique female connector and a compatible male pipe end. O-rings, located inside the female connector, provide the fuel seal. Integral locking tabs inside the female connector hold the fittings together.

Scheme 63

The fuel rail assembly (1) attaches to the cylinder head. The fuel rail assembly performs the following functions

1. Positions the fuel injectors (3) in the cylinder head
2. Distributes fuel evenly to the injectors

Scheme 64

The Multec 2 fuel injector assembly is a solenoid device controlled by the control module that meters pressurized fuel to a single engine cylinder. The control module energizes the high-impedance, 12 ohms, injector solenoid (2) to open a normally closed ball valve (3). This allows fuel to flow into the top of the injector, past the ball valve, and through a director plate at the injector outlet. The director plate has four machined holes that control the fuel flow, generating a spray of finely atomized fuel at the injector tip. Fuel from the injector tip is directed at the intake valve, causing the fuel to become further atomized and vaporized before entering the combustion chamber. This fine atomization improves fuel economy and emissions.

Starting Mode

When the ignition is first turned ON, the control module energizes the fuel pump relay for 2 seconds. This allows the fuel pump to build pressure in the fuel system. The control module calculates the air/fuel ratio based on inputs from the engine coolant temperature (ECT), manifold absolute pressure (MAP), and throttle position (TP) sensors. The system stays in starting mode until the engine speed reaches a predetermined RPM.

Clear Flood Mode

If the engine floods, clear the engine by pressing the accelerator pedal down to the floor and then crank the engine. When the TP sensor is at wide open throttle (WOT), the control module reduces the fuel injector pulse width in order to increase the air to fuel ratio. The control module holds this injector rate as long as the throttle stays wide open and the engine speed is below a predetermined RPM. If the throttle is not held wide open, the control module returns to the starting mode.

Run Mode

The run mode has 2 conditions called Open Loop and Closed Loop. When the engine is first started and the engine speed is above a predetermined RPM, the system begins Open Loop operation. The control module ignores the signal from the heated oxygen sensor (HO2S). The control module calculates the air/fuel ratio based on inputs from the ECT, MAP, and TP sensors. The system stays in Open Loop until meeting the following conditions

1. The HO2S has varying voltage output, showing that the HO2S is hot enough to operate properly.
2. The ECT sensor is above a specified temperature.
3. A specific amount of time has elapsed after starting the engine.

Specific values for the above conditions exist for each different engine, and are stored in the electrically erasable programmable read-only memory (EEPROM). The system begins Closed Loop operation after reaching these values. In Closed Loop, the control module calculates the air/fuel ratio, injector ON time, based upon the signal from various sensors, but mainly from the HO2S. This allows the air/fuel ratio to stay very close to 14.7:1.

Acceleration Mode

When the driver pushes on the accelerator pedal, air flow into the cylinders increases rapidly. To prevent possible hesitation, the control module increases the pulse width to the injectors to provide extra fuel during acceleration. This is also known as power enrichment. The control module determines the amount of fuel required based upon the TP, the ECT, the MAP, and the engine speed.

Deceleration Mode

When the driver releases the accelerator pedal, air flow into the engine is reduced. The control module monitors the corresponding changes in the TP, and the MAP. The control module shuts OFF fuel completely if the deceleration is very rapid, or for long periods, such as long, closed-throttle coast-down. The fuel shuts OFF in order to prevent damage to the catalytic converters.

Battery Voltage Correction Mode

When the battery voltage is low, the control module compensates for the weak spark delivered by the ignition system in the following ways

1. Increasing the amount of fuel delivered
2. Increasing the idle RPM
3. Increasing the ignition dwell time

Fuel Cutoff Mode

The control module cuts OFF fuel from the fuel injectors when the following conditions are met in order to protect the powertrain from damage and improve driveability

1. The ignition is OFF. This prevents engine run-on.
2. The ignition is ON but there is no ignition reference signal. This prevents flooding or backfiring.
3. The engine speed is too high, above red line.
4. The vehicle speed is too high, above rated tire speed.
5. During an extended, high speed, closed throttle coast down-This reduces emissions and increases engine braking.
6. During extended deceleration, in order to prevent damage to the catalytic converters.

Fuel Trim

The control module controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. The control module monitors the HO2S signal voltage while in Closed Loop and regulates the fuel delivery by adjusting the pulse width of the injectors based on this signal. The ideal fuel trim values are around 0 percent for both short and long term fuel trim. A positive fuel trim value indicates the control module is adding fuel in order to compensate for a lean condition by increasing the pulse width. A negative fuel trim value indicates that the control module 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 long and short term fuel trim values. The short term fuel trim values change rapidly in response to the HO2S signal voltage. These changes fine tune the engine fueling. The long term fuel trim makes coarse adjustments to fueling in order to re-center and restore control to short term fuel trim. A scan tool can be used to monitor the short and long term fuel trim values. The long term fuel trim diagnostic is based on an average of several of the long term speed load learn cells. The control module selects the cells based on the engine speed and engine load. If the control module detects an excessively lean or rich condition, the control module will set a fuel trim diagnostic trouble code (DTC).

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 Canister Purge Solenoid Valve

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

EVAP Canister Vent Solenoid Valve

The EVAP canister vent solenoid valve controls fresh airflow into the EVAP canister. The valve is normally open. The control module will command the solenoid closed 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. As FTP increases, FTP sensor voltage decreases, high pressure equal low voltage. As FTP decreases, FTP voltage increases, low pressure or vacuum equal high voltage.

EVAP Service Port

The EVAP service port is located in the EVAP purge pipe between the EVAP canister 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 permanent magnet generator, known as a variable reluctance sensor. The magnetic field of the sensor is altered by a crankshaft mounted reluctor wheel that has seven machined slots, six of which are equally spaced 60 degrees apart. The seventh slot is spaced 10 degrees after one of the 60 degree slots. The CKP sensor produces seven pulses for each revolution of the crankshaft. The pulse from the 10 degree slot is known as the sync pulse. The sync pulse is used to synchronize the coil firing sequence with the crankshaft position. The CKP sensor is connected to the PCM by a signal circuit and a low reference circuit.

Camshaft Position (CMP) Sensor

The camshaft position (CMP) sensor is triggered by a notched reluctor wheel built into the exhaust camshaft sprocket. The CMP sensor provides six signal pulses every camshaft revolution. Each notch, or feature of the reluctor wheel is of a different size for individual cylinder identification. This means the CMP and CKP signals are pulse width encoded to enable the PCM to constantly monitor their relationship. This relationship is used to determine camshaft actuator position and control its phasing at the correct value. The PCM also uses this signal to identify the compression stroke of each cylinder, and for sequential fuel injection. The CMP sensor is connected to the PCM by a 12-volt, low reference, and signal circuit.

Ignition Coils

Each ignition coil has an ignition 1 feed and a ground. The PCM supplies an ignition control (IC) circuit. Each ignition coil contains a solid state driver module as its primary element. The PCM signals the coil driver to initiate a firing event by applying the IC circuit voltage for the appropriate time or dwell. When the voltage is removed, the coil fires the spark plug. The coils are current-limited to prevent overloading if the IC current is held high too long. The spark plugs are tipped with platinum for long wear and higher efficiency.

Powertrain Control Module (PCM)

The PCM controls all ignition system functions, and constantly corrects the spark timing. The PCM 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 sensors (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.

Air Cleaner Restriction Indicator

The air cleaner restriction indicator is located on the intake duct between the air cleaner assembly and the throttle body.

If the area inside of the clear section is green, no air filter service is required. If the area inside the clear section is orange and Change Air Filter appears, replace the air filter.