Engine Controls (Introduction) -- 3.5L (L66): Diagnosis Saturn VUE I

Action Taken When the DTC Sets - Type A

The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.

Action Taken When the DTC Sets - Type B

The control module illuminates the MIL on the second consecutive ignition cycle that the diagnostic runs and fails.

Conditions for Clearing the MIL/DTC - Type A or Type B

1. The control module turns OFF the MIL after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC Last Test Failed clears when the diagnostic runs and passes.
3. Use a scan tool in order to clear the MIL and the DTC.

Non-Emissions Related DTCs

Action Taken When the DTC Sets - Type C

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The MIL will not illuminate.
3. The Service Vehicle Soon indicator on the instrument panel may illuminate.

Action Taken When the DTC Sets - Type D

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The MIL will not illuminate.

Conditions for Clearing the DTC - Type C or Type D

1. A last test failed, or current DTC, clears when the diagnostic runs and passes.
2. Use a scan tool in order to clear the DTC.

Diagnostic Trouble Code (DTC) Type(s)

Diagnostic Trouble Code (DTC) Type(s)

Scheme 84

Scheme 85

Idle Speed Inspection

1. Install a scan tool.
2. Ensure that all electrical loads and accessories are OFF.
3. Turn OFF the air conditioning.
4. Ensure that the vehicle is in PARK or NEUTRAL.
5. Start and run the engine until the ECT is at least 80°C (176°F).
6. Ensure that the scan tool data parameter Engine at Operating Temperature says YES.
7. Observe that the engine speed is 730 RPM +/-50 RPM with the scan tool.
8. Idle the engine for 1 minute with the AC ON and the blower motor operating on HIGH.
9. Observe that the engine speed is 730 RPM +/-50 RPM with the scan tool.
10. Compare the engine speed at idle with the scan tool to the following specifications: All engine accessories OFF-730 RPM +/-50 RPM Turn the AC ON and the heater fan on HIGH-730 RPM +/-50 RPM
11. If the scan tool indicated that the engine idle was within the specified values, the idle speed is normal.
12. If the scan tool indicated that the engine idle was more than or less than specified values, refer to «Rough, Unstable, or Incorrect Idle and Stalling»(ref-188837-S26150444692005090200000) .

Inspection Procedure

Note. Refer to Clean, Dry, Low Pressure Gas Source Notice in Cautions and Notices.

1. Turn OFF the ignition.
2. Remove the EVAP canister purge valve. Refer to «Evaporative Emission (EVAP) Canister Purge Solenoid Valve Replacement»(ref-188786-S21196768692005090200000) .
3. Lightly tap the EVAP canister purge valve on a hard surface.
4. Inspect for carbon particles exiting either of the vacuum ports. If no carbon particles were detected, but a blockage was detected during a diagnostic procedure, install the original EVAP canister purge valve. Continue with the cleaning procedure. If carbon particles are found during the inspection procedure, continue with the cleaning procedure. If a diagnostic procedure directed you to replace the EVAP canister purge valve and no carbon particles were detected, replace the EVAP canister purge valve. Return to the published service procedure.

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-188786-S18194948442005090200000) . An excessively wide electrode gap can prevent correct spark plug operation. Inspect for the correct spark plug torque. Refer to «Ignition System Specifications»(ref-188786-S18194948442005090200000) . Insufficient torque can prevent correct spark plug operation. An over torqued spark plug, causes the insulator (2) to crack. 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 a broken, worn, or loose center electrode (4) by shaking the spark plug. A rattling sound indicates internal damage. A loose center electrode (4) reduces the spark intensity. 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.
5. Inspect the spark plug recess area of the cylinder head for debris. Dirty or damaged threads can cause the spark plug not to seat correctly during installation.

Spark Plug Visual Inspection

1. Normal operation-Brown to grayish-tan with small amounts of white powdery deposits are normal combustion by-products from fuels with additives.
2. Carbon Fouled-Dry, fluffy black carbon, or soot caused by the following conditions: Rich fuel mixtures Leaking fuel injectors Excessive fuel pressure Restricted air filter element Incorrect combustion Reduced ignition system voltage output Weak coils Worn ignition wires Incorrect spark plug gap Excessive idling or slow speeds under light loads can keep spark plug temperatures so low that normal combustion deposits may not burn off.
3. Deposit Fouling-Oil, coolant, or additives that include substances such as silicone, very white coating, reduces the spark intensity. Most powdery deposits will not effect spark intensity unless they form into a glazing over the electrode.

PCM Long Term Memory and Engine Off Diagnostics

Several ignition positive voltage circuits supply battery power to the PCM even when the ignition switch is turned OFF. The continuous battery power enables the PCM to support a long term memory. The long term memory provides storage of diagnostic trouble codes, diagnostic test status, and the aforementioned "learned values" that improve driveability.

Another use of continuous battery power is the PCM can run certain system diagnostics with the engine off. One of these diagnostics is the engine off natural vacuum (EONV) EVAP system leak test. With the engine OFF, the PCM can turn on the main relay and provide power to operate the EVAP solenoids while monitoring the fuel tank pressure. During the running of the EONV diagnostic routine, the PCM can be fully powered up for as long as 30 minutes.

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.

Large Leak Test

This tests for large leaks and blockages in the evaporative emission (EVAP) system. The control module will command the EVAP vent valve ON, closed, and command the EVAP purge valve ON, open, with the engine running, allowing engine vacuum into the EVAP system. The control module monitors the fuel tank pressure (FTP) sensor voltage to verify that the system is able to reach a predetermined level of vacuum within a set amount of time. The control module then commands the EVAP purge valve OFF, closed, sealing the system and monitors the vacuum level for decay. If the control module does not detect that the predetermined vacuum level was achieved, or the vacuum decay rate is more than a calibrated level on 2 consecutive tests, DTC P0455 sets.

Small Leak Test

The engine off natural vacuum, (EONV), diagnostic is the small leak detection diagnostic for the evaporative emission (EVAP) system. The EONV diagnostic monitors the EVAP system pressure or vacuum with the key OFF. The EONV utilizes the temperature changes and the resulting naturally occurring vacuum or pressure in the fuel tank immediately following a drive cycle. When the vehicle is driven, the temperature in the fuel tank rises. When the vehicle is parked with the engine OFF and key OFF, the temperature in the fuel tank will continue to rise for a period of time, and then begin to decrease. The EONV diagnostic relies on this temperature change, and the corresponding pressure change to determine if an EVAP system leak is present. The EONV diagnostic is designed to detect leaks as small as 0.51 mm (0.020 in). The diagnostic can determine if a small leak is present based on vacuum or pressure readings in the EVAP system. When the EVAP system is sealed a finite amount of pressure or vacuum will be observed. When a 0.51 mm (0.020 in) leak is present, little or no pressure or vacuum is observed. If the test reports a failing value, DTC P0442 will set.

Canister Vent Restriction Test

If the evaporative emission (EVAP) vent system is restricted, fuel vapors will not be properly purged from the EVAP canister. The control module tests this by commanding the EVAP purge valve ON, open; and commanding the EVAP vent valve OFF, open; and monitoring the fuel tank pressure (FTP) sensor for an increase in vacuum. If vacuum increases more than a calibrated value, DTC P0446 sets.

Purge Valve Leak Test

If the evaporative emission (EVAP) purge valve does not seal properly, fuel vapors could enter the engine at an undesired time, causing driveability concerns. The control module tests for this by commanding the EVAP purge valve OFF, closed; and vent valve ON, closed; sealing the system, and monitoring the fuel tank pressure (FTP) for an increase in vacuum. If the control module detects that EVAP system vacuum increases above a calibrated value, DTC P0496 sets.