Engine Control System - 1.8L (LV6) - Introduction: Diagnosis Pontiac Vibe I рестайлинг

Diagnostic Trouble Code (DTC) Type(s)

Diagnostic Trouble Code (DTC) Type(s)

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Spark Plug Inspection

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-200094-S32396014332005102000000) 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

Spark Plug Inspection

1. Inspect the terminal post (1) for damage. Inspect for a bent or broken terminal post (1). Test for a loose terminal post (1) by twisting and pulling the post. The terminal post (1) should NOT move.
2. Inspect the insulator (2) for flashover or carbon tracking, soot. This is caused by the electrical charge traveling across the insulator (2) between the terminal post (1) and ground. Inspect for the following conditions: Inspect the spark plug boot for damage. Inspect the spark plug recess area of the cylinder head for moisture, such as oil, coolant, or water. A spark plug boot that is saturated causes arcing to ground.
3. Inspect the insulator (2) for cracks. All or part of the electrical charge may arc through the crack instead of the electrodes (3, 4).
4. Inspect for evidence of improper arcing. Measure the gap between the center electrode (4) and the side electrode (3) terminals. Refer to «Ignition System Specifications»(ref-200094-S32396014332005102000000) . An excessively wide electrode gap can prevent correct spark plug operation. Inspect for signs of tracking that occurred near the insulator tip instead of the center electrode (4). Inspect for a broken or worn side electrode (3). Inspect for bridged electrodes (3, 4). Deposits on the electrodes (3, 4) reduce or eliminates the gap. Inspect for worn or missing platinum pads on the electrodes (3, 4), if equipped. Inspect for excessive fouling.

Spark Plug Visual Inspection

1. Normal Spark Plug Operation Results in brown to grayish tan deposits on the area of the spark plug that enters the cylinder. A small amount of reddish brown, yellow, and white powdery residue may also be present on the insulator tip around the center electrode. These deposits are normal combustion by-product of fuels and lubricating oils which contain additives.
2. Carbon Fouling Indicated by dry carbon deposits on the portion of the spark plug inside of the cylinder. Excessive idling and driving at slower speeds under light engine loads can keep the spark plug temperatures so low that these deposits are not burned off. Rich fuels or poor ignition system output may cause carbon fouling. A spark plug of the incorrect heat range may cause carbon fouling. Carbon deposits on the spark plug insulator tip may become conductive and cause the high voltage arc to track along the tip to some point where the high voltage arcs to join the spark plug shell. This arc ignites the air fuel mixture later than normal which, in effect, retards the ignition timing. Heavy carbon deposits may be conductive to the extent that the arc path now becomes a shunt path to the spark plug shell, which prevents the spark from igniting the air/fuel mixture. A power and fuel loss results. The spark plug may be permanently damaged by arc tracking and must be replaced.
3. Oil Fouling Oil fouling appears as wet oily deposits on the portion of the spark plug inside of the cylinder. Oil getting past worn piston rings can leave oil deposits on the spark plug. Breaking in a new or recently overhauled engine can sometimes leave oil deposits on spark plugs.
4. Deposit Fouling Deposit fouling occurs when the normal reddish brown, yellow, or white deposits of combustion by-products become sufficient enough to cause misfiring. In some cases, these deposits melt and form a shiny glaze on the insulator around the center electrode. If the fouling is found only in one or two of the cylinders, valve stem clearances or the intake valve seals may be allowing excess lubricating oil to enter the cylinder, particularly if the deposits are heavier on the intake valve side of the spark plug.
5. Bridged Electrodes Fouling deposits between the electrodes ground out the high voltage necessary to fire the spark plug. The arc between electrode does not occur and the air fuel mixture is not ignited. Fuel remains unburned and a power loss results.
6. Flashover Flashover can occur when a damaged spark plug boot permits high voltage to short over the insulator to the spark plug shell or to the engine. Dirt, oil, and moisture may contribute to the formation of deposits that can lead to carbon tracking. Whenever a flashover occurs carbon is deposited allowing the arcing voltage to build a regular path to ground.
7. Excessive Gap The air space between the center and side electrodes at the bottom of the spark plug is too wide for consistent firing. This may be due to improper gap adjustment or to excessive wear of the electrodes during use. Excessive electrode wear on low mileage spark plugs may indicate vehicle operation at speeds higher than the speeds for which the engine was designed. Excessive electrode wear on low mileage spark plugs may indicate that the spark plug's heat range is too high. Electrode wear may also be the result of combustion gasses leaking past the spark plug threads. Excessively lean fuel may also cause electrode wear. Excessive electrode wear can prevent the high voltage from arcing across the electrodes. Fuel remains unburned and a power loss results. A gap that is too small may cause idling instability.
8. Incorrect Torque or Installation Incorrect torque or seating can cause a spark plug to run hot. This can lead to excessive electrode wear and an incorrect gap. In extreme cases, an over torqued or under torqued spark plug can cause exhaust blowby. The cylinder head seats must make good contact for sufficient heat transfer and spark plug cooling. Dirty or damaged threads in the head or on the spark plug can keep the spark plug from seating even though the proper torque is applied. Once the spark plugs are properly seated, tighten the spark plugs properly.
9. Cracked or Broken Insulators Usually, cracked insulators or broken insulators are the result of incorrect installation or of heat shock. Heat shock is a rapid increase in the insulator tip temperature which causes the insulator material to crack. The upper insulators can be broken when a poorly-fitting tool is used during servicing, or when the spark plug is hit from the outside. Cracks in the upper insulator may be inside the shell or invisible. The breakage may not cause problems until oil or water penetrates the crack later. A crack in the insulator causes the high voltage to ground out. The spark does not jump the electrode gap and the air fuel mixture is not ignited. Fuel is unburned and power is lost. Damage may result during gapping when the tool is pushed against the center electrode or the surrounding insulator, causing the insulator to crack. Bend only the side electrode when gapping a spark plug.
10. Corona Discharge Corona discharge is a steady blue light appearing around the insulator just above the shell crimp. Corona discharge is the visible evidence of a high tension field and does not have an effect on ignition system performance. The discharge may repel dust particles and leave a clear ring on the insulator just above the shell. This ring is sometimes mistaken for evidence that combustion gasses have blown between the shell and the insulator. Do not mistake corona discharge for flashover or for a shorted insulator.

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The powertrain control module (PCM) is a precision 32-bit microprocessor and is an essential part of the electronic control system. The PCM is responsible for such major functions as control of the fuel injectors, the idle air control (IAC) valve, the fuel pump relay, etc. The PCM (1) is located below the instrument panel (IP) storage compartment. Communication with the PCM is through the data link connector (2) located on the left side below the IP.

The PCM performs the OBD II diagnostic tests of the emission related systems. The PCM supplies a buffered voltage, called reference voltage, to the various information sensors and switches. The PCM controls most components with an electronic switch that completes a ground circuit when turned ON. The electronic switch is commonly referred to as an output driver. The PCM is also responsible for a self-diagnosis function and a fail-safe function.

Self-Diagnosis Function

The powertrain control module (PCM) diagnoses any troubles which may occur in the engine control system when the ignition switch is in the ON position with the engine running. The PCM indicates a malfunction by illuminating the malfunction indicator lamp (MIL) when a fault occurs in any of the following systems

1. The heated oxygen sensor 1 (HO2S 1)
2. The heated oxygen sensor 2 (HO2S 2)
3. The engine coolant temperature (ECT) sensor
4. The accelerator pedal position (APP) sensors
5. The throttle position (TP) sensors
6. The vehicle speed sensor (VSS)
7. The intake air temperature (IAT) sensor
8. The mass air flow (MAF) sensor
9. The camshaft position (CMP) sensor
10. The crankshaft position (CKP) sensor
11. The knock sensor (KS) system
12. The evaporative emission (EVAP) control system
13. The idle air control (IAC) system
14. The electronic throttle control (ETC) or throttle actuator control (TAC) system
15. The CMP actuator solenoid system
16. The misfire detection
17. The fuel-trim
18. The catalyst monitor
19. The central processing unit (CPU) of the PCM

When the PCM detects a malfunction in one of the above areas, the PCM will illuminate or flash the MIL in order to notify the driver of the occurrence of a fault.

Reading Diagnostic Trouble Codes

The procedure for reading diagnostic trouble codes is to use a diagnostic scan tool. Follow the instructions supplied by the scan tool manufacturer in order to read DTCs accurately.

Clearing Diagnostic Trouble Codes

The PCM will begin to count the warm-up cycles when the fault that caused the DTC to be stored into memory has been corrected. The DTC will automatically be cleared from the PCM memory when the PCM has counted 40 consecutive warm-up cycles with no further faults detected.

Diagnostic trouble codes (DTCs) can be cleared using a scan tool. In order to clear DTCs, use the scan tools Clear DTC Information function. Follow the instructions supplied by the scan tool manufacturer.

Vacuum Leak Pump and Reference Orifice Test

The first two events of the EVAP system diagnostic checks the operation of the vacuum leak pump and for a restriction in the reference orifice. With the purge solenoid and the vent solenoid both OFF, atmospheric pressure should enter the EVAP system and be detected by the FTP sensor. If atmospheric pressure is not detected, the reference orifice may be plugged. During event two, the vacuum leak pump is turned ON and the FTP sensor should indicate negative pressure within a specified value. If the pressure change is too small, a DTC P043E can set. If the pressure change is too large, a DTC P043F can set. If atmospheric pressure is measured in event one, but no negative pressure is measured in event two, an inoperative vacuum leak pump is indicated, and a DTC P2401 can set. If there is a sudden large increase in negative pressure when the pump is turned ON, a stuck on vent solenoid may be indicated and a DTC P2419 can set.

Evaporative Emission (EVAP) Control System Description (FWD)

Large Leak test

Event three tests for a large leak in the EVAP system. The PCM commands the EVAP vent valve ON, CLOSED, sealing the EVAP system. This allows the vacuum pump to create a large increase in negative pressure. If the expected increase in negative pressure is not achieved, a large leak is indicated and a DTC P0455 can set. If there is no change in pressure when the vent solenoid is turned ON, the vent solenoid may be inoperative and a DTC P2420 can set.

Evaporative Emission (EVAP) Control System Description (FWD)

Small Leak Test

If the large leak test passes, the PCM will continue to monitor the FTP sensor signal in order to determine if there is small leak. If a specified minimum value is not achieved or the minimum value can not be maintained, a DTC P0456 can set. This diagnostic can detect leaks as small as 0.5 millimeter (0.020 inch) between the fuel fill cap and the purge valve.

Evaporative Emission (EVAP) Control System Description (FWD)

EVAP Purge Valve Test

In event four of the EVAP system diagnostic, the purge solenoid is turned ON, OPEN, causing a drop in negative pressure. If the FTP sensor does not detect a significant decrease in vacuum pressure, a DTC P0441 will set.

Evaporative Emission (EVAP) Control System Description (FWD)

Final Test

In event five all of the EVAP components return to the same state they were in event one. Because the vacuum pump remained ON in event four, the FTP sensor still detected a small vacuum. Now, with all components OFF, the pressure should return to atmosphere, indicating there are is no blockage or restrictions in the EVAP system.

Evaporative Emission (EVAP) Control System Description (FWD)

This tests for large leaks and blockages in the EVAP system. The PCM will command the EVAP vent valve ON, closed and the purge valve and the vacuum pressure switching solenoid ON, open with the engine running. This allows engine vacuum into the EVAP system. The PCM then commands the purge valve OFF, closed sealing the system. The PCM then monitors the fuel tank pressure (FTP) sensor signal in order to determine if there is vacuum decay. A rise or rapid increase in pressure indicates there is a large leak in the evaporative emission system. If the PCM detects the vacuum level was not achieved and vacuum decay was evident for two consecutive trips, the Malfunction Indicator Lamp (MIL) will be illuminated, and a DTC P0442 will set.

If the large leak test passes the PCM will continue to monitor the fuel tank pressure (FTP) sensor signal in order to determine if there is vacuum decay. A slight increase or rise in pressure indicates there is a small leak in the evaporative emission system. The EVAP control system is required to detect evaporative emission fuel system leaks as small as 0.5 millimeter (0.020 inch) between the fuel fill cap and the purge valve. If the PCM detects vacuum decay was evident for two consecutive trips, the MIL will be illuminated, and a DTC P0456 will set.