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

Testing & Diagnostics 2 illustrations ~800 words

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.

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 driver information center, if equipped, may display a message.

Conditions for Clearing the DTC - Type C

  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.

Conditions for Clearing the DTC - Type X

This DTC is available in the PCM software, but has been disabled, or turned OFF. In this case, the diagnostic does not run, no DTCs are stored, and the MIL does not illuminate. Type X DTCs are used primarily for export vehicles that do not require MIL illumination or DTC storing.

Diagnostic Trouble Code (DTC) Type(s)

Diagnostic Trouble Code (DTC)Domestic/Export
DTC P0010B
DTC P0011A
DTC P0013B
DTC P0014A
DTC P0016A
DTC P0017A
DTC P0018A
DTC P0019A
DTC P0020B
DTC P0021A
DTC P0023B
DTC P0024A
DTC P0030B
DTC P0031B
DTC P0032B
DTC P0036B
DTC P0037B
DTC P0038B
DTC P0050B
DTC P0051B
DTC P0052B
DTC P0056B
DTC P0057B
DTC P0058B
DTC P0068B
DTC P0101B
DTC P0102B
DTC P0103B
DTC P0106B
DTC P0107B
DTC P0108B
DTC P0112B
DTC P0113B
DTC P0116B
DTC P0117B
DTC P0118B
DTC P0122A
DTC P0123A
DTC P0125B
DTC P0128B
DTC P0131B
DTC P0132B
DTC P0133B
DTC P0135B
DTC P0137B
DTC P0138B
DTC P0139B
DTC P0140B
DTC P0141B
DTC P0151B
DTC P0152B
DTC P0153B
DTC P0155B
DTC P0157B
DTC P0158B
DTC P0159B
DTC P0160B
DTC P0161B
DTC P0171B
DTC P0172B
DTC P0174B
DTC P0175B
DTC P0201B
DTC P0202B
DTC P0203B
DTC P0204B
DTC P0205B
DTC P0206B
DTC P0207B
DTC P0208B
DTC P0222A
DTC P0223A
DTC P0261B
DTC P0262B
DTC P0264B
DTC P0265B
DTC P0267B
DTC P0268B
DTC P0270B
DTC P0271B
DTC P0273B
DTC P0274B
DTC P0276B
DTC P0277B
DTC P0279B
DTC P0280B
DTC P0282B
DTC P0283B
DTC P0300B
DTC P0301B
DTC P0302B
DTC P0303B
DTC P0304B
DTC P0305B
DTC P0306B
DTC P0307B
DTC P0308B
DTC P0315A
DTC P0325B
DTC P0326B
DTC P0330B
DTC P0331B
DTC P0335A
DTC P0336B
DTC P0340B
DTC P0341B
DTC P0345B
DTC P0346B
DTC P0351B
DTC P0352B
DTC P0353B
DTC P0354B
DTC P0355B
DTC P0356B
DTC P0357B
DTC P0358B
DTC P0365B
DTC P0366B
DTC P0390B
DTC P0391B
DTC P0420B
DTC P0430B
DTC P0442B
DTC P0443B
DTC P0446B
DTC P0449B
DTC P0451B
DTC P0452B
DTC P0453B
DTC P0454C
DTC P0455B
DTC P0458B
DTC P0459B
DTC P0496B
DTC P0498B
DTC P0499B
DTC P0506B
DTC P0507B
DTC P0601A
DTC P0602A
DTC P0604A
DTC P0606A
DTC P0607A
DTC P0628C
DTC P0629C
DTC P0638A
DTC P0641A
DTC P0650A
DTC P0651A
DTC P0686C
DTC P0687C
DTC P0689C
DTC P0690C
DTC P0700A
DTC P1101A
DTC P1111C
DTC P1112C
DTC P1114C
DTC P1115C
DTC P1137B
DTC P1138B
DTC P1157B
DTC P1158B
DTC P1380C
DTC P1381C
DTC P167AA
DTC P167BA
DTC P2088B
DTC P2089B
DTC P2090B
DTC P2091B
DTC P2092B
DTC P2093B
DTC P2094B
DTC P2095B
DTC P2096B
DTC P2097B
DTC P2098B
DTC P2099B
DTC P2100A
DTC P2101A
DTC P2108A
DTC P2119A
DTC P2122A
DTC P2123A
DTC P2127A
DTC P2128A
DTC P2135A
DTC P2138A
DTC P2176A
DTC P2231B
DTC P2234B
DTC P2237B
DTC P2240B
DTC P2243B
DTC P2247B
DTC P2251B
DTC P2254B
DTC P2300B
DTC P2301B
DTC P2303B
DTC P2304B
DTC P2306B
DTC P2307B
DTC P2309B
DTC P2310B
DTC P2312B
DTC P2313B
DTC P2315B
DTC P2316B
DTC P2318B
DTC P2319B
DTC P2321B
DTC P2322B
DTC P2626C
DTC P2629B
DTC P2636C

Diagnostic Trouble Code (DTC) Type(s)

Scheme 87

Scheme 87: Evaporative Emissions (EVAP) Hose Routing Diagram
CalloutComponent Name
1EVAP Canister Purge Solenoid Valve
2EVAP Canister
3Fuel Fill Neck/Fill Cap
4Rollover Valve/Fuel Tank Pressure (FTP) Sensor
5Fuel Tank
6EVAP Canister Vent Solenoid Valve
7Vent Hose/Pipe
8EVAP Vapor Pipe
9EVAP Purge Pipe
10EVAP Service Port

Scheme 88

Scheme 88: Fuel Hose/Pipes Routing Diagram
CalloutComponent Name
1Jet Pump and Fuel Sender Assembly
2Fuel Pump and Fuel Sender Assembly
3Fuel Feed Hose
4Fuel Feed Pipe
5Fuel Rail and Injectors
6Fuel Pressure Test Connection
7Fuel Filter
8Fuel Return Hose
9Fuel Filler Tube
10Fuel Tank Pressure (FTP) Sensor
11Fuel Level Vent Valve (FLVV)
12Fuel Tank

Large Leak Test

This tests for large leaks and blockages in the evaporative emission (EVAP) system. The control module commands the EVAP vent solenoid valve ON and commands the EVAP purge solenoid valve ON, 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 solenoid valve OFF, 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 will set.

Small Leak Test

The engine off natural vacuum (EONV) diagnostic is the small-leak detection diagnostic for the evaporative emission (EVAP) system. While previous leak detection methods were performed with the engine running, the EONV diagnostic monitors the EVAP system pressure or vacuum with the ignition OFF. Because of this, it may be normal for the control module to remain active for up to 40 minutes after the ignition is turned OFF. This is important to remember when performing a parasitic draw test on vehicles equipped with EONV.

The EONV utilizes the temperature changes in the fuel tank immediately following a drive cycle to use the naturally occurring vacuum or pressure in the fuel tank. When the vehicle is driven, the temperature rises in the tank. After the vehicle is parked, the temperature in the tank continues to rise for a period of time, then starts to drop. The EONV diagnostic relies on this temperature change and the corresponding pressure change in a sealed system, 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 system is sealed, a finite amount of pressure or vacuum will be observed. When a 0.51 mm (0.020 in) leak is present, often 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 solenoid valve ON, commanding the EVAP vent solenoid valve OFF, and monitoring the fuel tank pressure (FTP) sensor for an increase in vacuum. If the vacuum increases more than a calibrated value, DTC P0446 will set.

Purge Solenoid Valve Leak Test

If the evaporative emission (EVAP) purge solenoid 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 solenoid valve OFF and the vent solenoid valve ON, sealing the system, and monitors the fuel tank pressure (FTP) for an increase in vacuum. If the control module detects that the EVAP system vacuum increases above a calibrated value, DTC P0496 will set.