Engine Control System - 3.8l - Introduction (2 of 2) Buick LaCrosse I

Temperature vs Resistance

Temperature vs Resistance

Altitude vs Barometric Pressure

Altitude vs Barometric Pressure

Ignition System Specifications

Ignition System Specifications

Fastener Tightening Specifications

Fastener Tightening Specifications

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 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) Type(s)

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Engine Controls Schematic Icons

Engine Controls Schematic Icons Icon Icon Definition NOTE: The OBD II symbol is used on the circuit diagrams in order to alert the technician that the circuit is essential for proper OBD II emission control circuit operation. Any circuit which fails and causes the malfunction indicator lamp (MIL) to turn ON or causes emissions-related component damage, is identified as an OBD II circuit

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Powertrain Control Module (PCM) Connector End Views

Powertrain Control Module (PCM) C1 (NU3) Connector Part Information OEM: 15460473 Service: See Catalog 56-Way F Micro-Pack 64 Series (BU) Pin Wire Color Circuit No. Function 1-3 - - Not Used 4 GY 2700 5-Volt Reference 5 - - Not Used 6 BN/WH 419 MIL Control 7 BK 2751 Low Reference 8 BK 2759 Low Reference 9 - - Not Used 10 WH 1310 EVAP Canister Vent Solenoid Valve Control 11 - - Not Used 12 BK 476 Low Reference 13-14 - - Not Used 15 D-GN 1049 PCM Class 2 Serial Data 16-17 - - Not Used 18 BN 1141 Ignition 3 Voltage 19 PK 439 Ignition 1 Voltage 20 OG 540 Battery Positive Voltage 21 WH 121 Engine Speed Signal (JL9) 22 D-GN 389 Vehicle Speed Signal 23 YE/BK 625 Starter Enable Relay Control 24 BN 5069 Powertrain Relay Control 25 - - Not Used 26 D-GN 890 Fuel Tank Pressure Sensor Signal 27-30 - - Not Used 31 RD/BK 380 A/C Refrigerant Pressure Sensor Signal 32 WH 17 Stop Lamp Switch Signal 33 D-GN/WH 459 A/C Compressor Clutch Relay Control 34 BN 436 Air Pump Relay Control 35-36 - - Not Used 37 D-GN/WH 465 Fuel Pump Relay Control 38-42 - - Not Used 43 PU 1589 Fuel Level Sensor Signal 44 GY 1884 Cruise Control Set/Coast and Resume/Accelerate Switch Signal 45-47 - - Not Used 48 D-GN 335 Low Speed Cooling Fan Relay Control 49 - - Not Used 50 D-BU 473 High Speed Cooling Fan Relay Control 51-52 - - Not Used 53 GY 2709 5-Volt Reference 54-56 - - Not Used

Powertrain Control Module (PCM) C1 (W/O NU3) Connector Part Information OEM: 15418488 Service: See Catalog 56-Way F Micro-Pack 64 Series (BU) Pin Wire Color Circuit No. Function 1-3 - - Not Used 4 GY 2700 5-Volt Reference 5 - - Not Used 6 BN/WH 419 MIL Control 7 BK 2751 Low Reference 8 BK 2759 Low Reference 9 - - Not Used 10 WH 1310 EVAP Canister Vent Solenoid Valve Control 11-14 - - Not Used 15 D-GN 1049 PCM Class 2 Serial Data 16-17 - - Not Used 18 BN 1141 Ignition 3 Voltage 19 PK 439 Ignition 1 Voltage 20 OG 540 Battery Positive Voltage 21 WH 121 Engine Speed Signal (JL9) 22 D-GN 389 Vehicle Speed Signal 23 YE/BK 625 Starter Enable Relay Control 24 BN 5069 Powertrain Relay Control 25 - - Not Used 26 D-GN 890 Fuel Tank Pressure Sensor Signal 27-30 - - Not Used 31 RD/BK 380 A/C Refrigerant Pressure Sensor Signal 32 WH 17 Stop Lamp Switch Signal 33 D-GN/WH 459 A/C Compressor Clutch Relay Control 34-36 - - Not Used 37 D-GN/WH 465 Fuel Pump Relay Control 38-42 - - Not Used 43 PU 1589 Fuel Level Sensor Signal 44 GY 1884 Cruise Control Set/Coast and Resume/Accelerate Switch Signal 45-47 - - Not Used 48 D-GN 335 Low Speed Cooling Fan Relay Control 49 - - Not Used 50 D-BU 473 High Speed Cooling Fan Relay Control 51-52 - - Not Used 53 GY 2709 5-Volt Reference 54-56 - - Not Used

Powertrain Control Module (PCM) C2 (NU3) Connector Part Information OEM: 15460475 Service: See Catalog 73-Way F Micro-Pack 64 Series (BK) Pin Wire Color Circuit No. Function 1 BN 1456 EGR Valve Position Signal 2 OG/BK 1061 UART Serial Data Secondary 3 TN 800 UART Serial Data Primary 4 BK/WH 845 Fuel Injector 5 Control 5 BK 1744 Fuel Injector 1 Control 6 YE/BK 846 Fuel Injector 6 Control 7 PK/BK 1746 Fuel Injector 3 Control 8 BK 2753 Low Reference 9 L-GN/BK 1745 Fuel Injector 2 Control 10 L-BU/BK 844 Fuel Injector 4 Control 11 TN/BK 424 IC Timing Signal 12 BK/WH 3112 HO2S Heater Low Control Sensor 1 13 RD 1676 EGR Solenoid High Control 14-15 - - Not Used 16 GY 435 EGR Solenoid Low Control 17 - - Not Used 18 L-GN 432 MAP Sensor Signal 19-25 - - Not Used 26 BK 630 Camshaft Position Signal 27 PU/WH 430 Low Resolution Engine Speed Signal 28 L-BU/BK 647 Medium Resolution Engine Speed Signal 29 BK 2761 Low Reference 30 OG/BK 469 Low Reference 31 BN 1174 Oil Level Switch Signal 32 - - Not Used 33 GY 2702 5-Volt Reference 34 GY 2704 5-Volt Reference 35 GY 474 5 Volt Reference 36 - - Not Used 37 RD/BK 453 Low Reference 38-40 - - Not Used 41 D-GN/WH 428 EVAP Canister Purge Solenoid Valve Control 42-44 - - Not Used 45 GY 23 Generator Field Duty Cycle Signal 46 D-BU 496 Knock Sensor 1 Signal 47 TN/WH 3111 HO2S Low Signal 48 PU/WH 3110 HO2S High Signal 49-52 - - Not Used 53 RD 225 Generator Turn On Signal 54 - - Not Used 55 YE 410 ECT Sensor Signal 56 - - Not Used 57 TN/BK 231 Oil Pressure Switch Signal 58 L-BU 1876 Knock Sensor 2 Signal 59 PK/BK 429 Air Solenoid Control 60 - - Not Used 61 WH 423 IC Timing Control 62-72 - - Not Used 73 BK/WH 451 Ground

Powertrain Control Module (PCM) C2 (W/O NU3) Connector Part Information OEM: 15462060 Service: See Catalog 73-Way F Micro-Pack 64 Series (BK) Pin Wire Color Circuit No. Function 1 BN 1456 EGR Valve Position Signal 2 OG/BK 1061 UART Serial Data Secondary 3 TN 800 UART Serial Data Primary 4 BK/WH 845 Fuel Injector 5 Control 5 BK 1744 Fuel Injector 1 Control 6 YE/BK 846 Fuel Injector 6 Control 7 PK/BK 1746 Fuel Injector 3 Control 8 BK 2753 Low Reference 9 L-GN/BK 1745 Fuel Injector 2 Control 10 L-BU/BK 844 Fuel Injector 4 Control 11 TN/BK 424 IC Timing Signal 12 BK/WH 3112 HO2S Heater Low Control Sensor 1 13 RD 1676 EGR Solenoid High Control 14-15 - - Not Used 16 GY 435 EGR Solenoid Low Control 17 - - Not Used 18 L-GN 432 MAP Sensor Signal 19-25 - - Not Used 26 BK 630 Camshaft Position Signal 27 PU/WH 430 Low Resolution Engine Speed Signal 28 L-BU/BK 647 Medium Resolution Engine Speed Signal 29 BK 2761 Low Reference 30 OG/BK 469 Low Reference 31 BN 1174 Oil Level Switch Signal 32 - - Not Used 33 GY 2702 5-Volt Reference 34 GY 2704 5-Volt Reference 35-36 - - Not Used 37 RD/BK 453 Low Reference 38-40 - - Not Used 41 D-GN/WH 428 EVAP Canister Purge Solenoid Valve Control 42-44 - - Not Used 45 GY 23 Generator Field Duty Cycle Signal 46 D-BU 496 Knock Sensor 1 Signal 47 TN/WH 3111 HO2S Low Signal 48 PU/WH 3110 HO2S High Signal 49-52 - - Not Used 53 RD 225 Generator Turn On Signal 54 - - Not Used 55 YE 410 ECT Sensor Signal 56 - - Not Used 57 TN/BK 231 Oil Pressure Switch Signal 58 L-BU 1876 Knock Sensor 2 Signal 59-60 - - Not Used 61 WH 423 IC Timing Control 62-72 - - Not Used 73 BK/WH 451 Ground

Powertrain Control Module (PCM) C3 (NU3) Connector Part Information OEM: 15460474 Service: See Catalog 56-Way F Micro-Pack 64 Series (GY) Pin Wire Color Circuit No. Function 1-3 - - Not Used 4 TN/WH 3121 HO2S Low Signal 5 YE/BK 1227 TFT Sensor Signal 6 YE 492 MAF Sensor Signal 7 - - Not Used 8 BK/WH 3122 HO2S Heater Low Control - Sensor 2 9-10 - - Not Used 11 RD/BK 1230 AT ISS High Signal 12 YE 400 VSS High Signal 13-14 - - Not Used 15 GY 773 Transmission Range Switch Signal C 16-18 - - Not Used 19 PU 3120 HO2S High Signal 20-21 - - Not Used 22 YE 772 Transmission Range Switch Signal B 23 WH 776 Transmission Range Switch Signal P 24 WH 1804 TCC Release Switch Signal 25 - - Not Used 26 TN 472 IAT Sensor Signal 27-30 - - Not Used 31 WH 5268 Air Pressure Sensor 32 - - Not Used 33 L-GN 1222 1-2 Shift Solenoid Valve Control 34 BK/WH 771 Transmission Range Switch Signal A 35-38 - - Not Used 39 TN/BK 422 TCC Solenoid Valve Control 40-43 - - Not Used 44 PU 401 VSS Low Signal 45 - - Not Used 46 YE/BK 1223 2-3 Shift Solenoid Valve Control 47 RD/BK 1228 PC Solenoid Valve High Control (Sol. A) 48 BK 452 Low Reference 49 D-BU/WH 1231 AT ISS Low Signal 50 BK 2760 Low Reference 51 L-BU/WH 1229 PC Solenoid Valve Low Control (Sol. A) 52-56 - - Not Used

Powertrain Control Module (PCM) C3 (W/O NU3) Connector Part Information OEM: 15418487 Service: See Catalog 56-Way F Micro-Pack 64 Series (GY) Pin Wire Color Circuit No. Function 1-3 - - Not Used 4 TN/WH 3121 HO2S Low Signal 5 YE/BK 1227 TFT Sensor Signal 6 YE 492 MAF Sensor Signal 7 - - Not Used 8 BK/WH 3122 HO2S Heater Low Control - Sensor 2 9-10 - - Not Used 11 RD/BK 1230 AT ISS High Signal 12 YE 400 VSS High Signal 13-14 - - Not Used 15 GY 773 Transmission Range Switch Signal C 16-18 - - Not Used 19 PU 3120 HO2S High Signal 20-21 - - Not Used 22 YE 772 Transmission Range Switch Signal B 23 WH 776 Transmission Range Switch Signal P 24 WH 1804 TCC Release Switch Signal 25 - - Not Used 26 TN 472 IAT Sensor Signal 27-32 - - Not Used 33 L-GN 1222 1-2 Shift Solenoid Valve Control 34 BK/WH 771 Transmission Range Switch Signal A 35-38 - - Not Used 39 TN/BK 422 TCC Solenoid Valve Control 40-43 - - Not Used 44 PU 401 VSS Low Signal 45 - - Not Used 46 YE/BK 1223 2-3 Shift Solenoid Valve Control 47 RD/BK 1228 PC Solenoid Valve High Control (Sol. A) 48 BK 452 Low Reference 49 D-BU/WH 1231 AT ISS Low Signal 50 BK 2760 Low Reference 51 L-BU/WH 1229 PC Solenoid Valve Low Control (Sol. A) 52-56 - - Not Used

Engine Controls Connector End Views

Accelerator Pedal Position (APP) Sensor Connector Part Information OEM: 15326829 Service: 88953153 6-Way F 150 Series Sealed (BK) Pin Wire Color Circuit No. Function A PU 1272 Low Reference B L-BU 1162 APP Sensor 2 Signal C TN 1274 5-Volt Reference D BN 1271 Low Reference E D-BU 1161 APP Sensor 1 Signal F WH/BK 1164 5-Volt Reference

Camshaft Position (CMP) Sensor Connector Part Information OEM: Assembly 12162279 Connector 12162272 Cable Seal 12092862 Connector Seal 12047908 Service: 12126476 3-Way F Metri-Pack 150.2 Series, Pull To Seat (GY) Pin Wire Color Circuit No. Function A BN/WH 633 CMP Sensor Signal B BK/WH 836 Low Reference C WH/BK 644 12-Volt Reference

Crankshaft Position (CKP) Sensor Connector Part Information OEM: Assembly 12162834 Connector 12162724 Connector Seal 12040756 Cable Seal 12078081 Service: See Catalog 4-Way F Metri-Pack 150.2 Series, Sealed, Pull-To-Seat Pin Wire Color Circuit No. Function A L-BU/WH 1800 CKP Sensor 2 Signal B YE 573 CKP Sensor 1 Signal C BK/WH 836 Low Reference D WH/BK 644 12-Volt Reference

Engine Coolant Temperature (ECT) Sensor Connector Part Information OEM: 12162193 Service: 88987183 2-Way F Metri-Pack 150.2 Pull To Seat Series Sealed (BK) Pin Wire Color Circuit No. Function A BK 2761 Low Reference B YE 410 ECT Sensor Signal

Evaporative Emission (EVAP) Canister Purge Solenoid Valve Connector Part Information OEM: 12052643 Service: 12101858 2-Way F Metri-Pack 150 Series Sealed (RD) Pin Wire Color Circuit No. Function A PK 339 Ignition 1 Voltage B D-GN/WH 428 EVAP Canister Purge Solenoid Valve Control

Evaporative Emission (EVAP) Canister Vent Solenoid Connector Part Information OEM: 12052643 Service: 12101858 2-Way F Metri-Pack 150 Series Sealed (RD) Pin Wire Color Circuit No. Function A OG 2840 Battery Positive Voltage B WH 1310 EVAP Canister Vent Solenoid Valve Control

Exhaust Gas Recirculation (EGR) Valve Connector Part Information OEM: 12186056 Service: 12126477 5-Way F Metri-Pack 150.2 Pull To Seat Series Sealed (BK) Pin Wire Color Circuit No. Function A GY 435 EGR Solenoid Low Control B BK 2753 Low Reference C BN 1456 EGR Valve Position Signal D GY 2702 5-Volt Reference E RD 1676 EGR Solenoid High Control

Fuel Injector 1 Connector Part Information OEM: 15421930 Service: See Catalog 2-Way F Metri-Pack 150 Series Sealed (BK) Pin Wire Color Circuit No. Function A PK 639 Ignition 1 Voltage B BK 1744 Fuel Injector 1 Control

Fuel Injector 2 Connector Part Information OEM: 15421930 Service: See Catalog 2-Way F Metri-Pack 150 Series Sealed (BK) Pin Wire Color Circuit No. Function A PK 639 Ignition 1 Voltage B L-GN/BK 1745 Fuel Injector 2 Control

Fuel Injector 3 Connector Part Information OEM: 15421930 Service: See Catalog 2-Way F Metri-Pack 150 Series Sealed (BK) Pin Wire Color Circuit No. Function A PK 639 Ignition 1 Voltage B PK/BK 1746 Fuel Injector 3 Control

Fuel Injector 4 Connector Part Information OEM: 15421930 Service: See Catalog 2-Way F Metri-Pack 150 Series Sealed (BK) Pin Wire Color Circuit No. Function A PK 639 Ignition 1 Voltage B L-BU/BK 844 Fuel Injector 4 Control

Fuel Injector 5 Connector Part Information OEM: 15421930 Service: See Catalog 2-Way F Metri-Pack 150 Series Sealed (BK) Pin Wire Color Circuit No. Function A PK 639 Ignition 1 Voltage B BK/WH 845 Fuel Injector 5 Control

Fuel Injector 6 Connector Part Information OEM: 15421930 Service: See Catalog 2-Way F Metri-Pack 150 Series Sealed (BK) Pin Wire Color Circuit No. Function A PK 639 Ignition 1 Voltage B YE/BK 846 Fuel Injector 6 Control

Fuel Pump and Sender Assembly Connector Part Information OEM: 15326631 Service: 15306360 4-Way F GT 280 Series Sealed (BK) Pin Wire Color Circuit No. Function A BK 150 Ground B PU 30 Fuel Level Sensor Signal C BK/WH 651 Ground D GY 120 Fuel Pump Supply Voltage

Fuel Tank Pressure Sensor Connector Part Information OEM: 12059595 Service: 88986451 3-Way F Metri-Pack 150 Series, Sealed (BK) Pin Wire Color Circuit No. Function A OG/BK 469 Low Reference B D-GN 890 Fuel Tank Pressure Sensor Signal C GY/BK 416 5-Volt Reference

Heated Oxygen Sensor (HO2S) 1 (W/O NU3) Connector Part Information OEM: 12160482 Service: See Catalog 4-Way F Metri-Pack 150 Series Sealed (BK) Pin Wire Color Circuit No. Function A TN/WH 3111 HO2S Low Signal B PU/WH 3110 HO2S High Signal C BK/WH 3112 HO2S Heater Low Control Sensor 1 D PK 839 Ignition 1 Voltage

Heated Oxygen Sensor (HO2S) 1 (NU3) Connector Part Information OEM: 12176896 Service: See Catalog 4-Way F Metri-Pack 150 Series Sealed (GY) Pin Wire Color Circuit No. Function A TN/WH 3111 HO2S Low Signal B PU/WH 3110 HO2S High Signal C BK/WH 3112 HO2S Heater Low Control Sensor 1 D PK 839 Ignition 1 Voltage

Heated Oxygen Sensor (HO2S) 2 Connector Part Information OEM: 15326423 Service: 15306319 4-Way M Metri-Pack 150 Series Sealed (GY) Pin Wire Color Circuit No. Function A TN/WH 3121 HO2S Low Signal B PU 3120 HO2S High Signal C BK/WH 3122 HO2S Heater Low Control Sensor 2 D PK 839 Ignition 1 Voltage

Ignition Control Module (ICM) Connector Part Information OEM: 12124379 Service: 12167123 14-Way F Metri-Pack 150 Pull To Seat Series Sealed (BK) Pin Wire Color Circuit No. Function A WH 423 IC Timing Control B TN/BK 424 IC Timing Signal C L-BU/BK 647 Medium Resolution Engine Speed Signal D PU/WH 430 Low Resolution Engine Speed Signal E - - Not Used F BK 630 Camshaft Position Signal G YE 573 CKP Sensor 1 Signal H L-BU/WH 1800 CKP Sensor 2 Signal J BN/WH 633 CMP Sensor Signal K BK/WH 51 Ground L RD/BK 453 Low Reference M BK/WH 836 Low Reference N WH/BK 644 12-Volt Reference P PK 239 Ignition 1 Voltage

Knock Sensor (KS) 1 Connector Part Information OEM: 12176800 Service: 15306070 1-Way F Metri-Pack 150 Series Sealed (GY) Pin Wire Color Circuit No. Function 1 D-BU 496 Knock Sensor 1 Signal

Knock Sensor (KS) 2 Connector Part Information OEM: 12176800 Service: 15306070 1-Way F Metri-Pack 150 Series Sealed (GY) Pin Wire Color Circuit No. Function 1 L-BU 1876 Knock Sensor 2 Signal

Manifold Absolute Pressure (MAP) Sensor Connector Part Information OEM: 12129946 Service: 12129946 3-Way F Metri-Pack 150 Series Sealed (GY) Pin Wire Color Circuit No. Function A OG/BK 469 Low Reference B L-GN 432 MAP Sensor Signal C GY 2704 5-Volt Reference

Mass Airflow (MAF)/Intake Air Temperature (IAT) Sensor Connector Part Information OEM: 15326822 Service: 15326822 5-Way F GT 150 Series Sealed (BK) Pin Wire Color Circuit No. Function A YE 492 MAF Sensor Signal B PK 339 Ignition 1 Voltage C BK/WH 451 Ground D TN 472 IAT Sensor Signal E BK 2760 Low Reference

Secondary Air Injection (AIR) Control Solenoid Valve/Pressure Sensor, Bank 2 (NU3) Connector Part Information OEM: 15460171 Service: See Catalog 6-Way F GT 150 Series Sealed (BK) Pin Wire Color Circuit No. Function 1 BK 476 Low Reference 2 WH 5268 Air Pressure Sensor Signal 3 GY 474 5-Volt Reference 4 BK/WH 451 Ground 5 - - Not Used 6 PU 421 Air Injection Reaction Solenoid Relay Coil Control

Secondary Air Injection (AIR) Pump (NU3) Connector Part Information OEM: 15326677 Service: 88953351 2-Way F GT 280 Series Sealed (BK) Pin Wire Color Circuit No. Function A RD 78 Air Pump Supply Voltage B BK 1050 Ground

Secondary Air Injection (AIR) Pump Relay (NU3) Connector Part Information OEM: 15336745 Service: 15306331 4-Way F GR 280 Series, Metri-Pack 800 Series, Sealed (GY) Pin Wire Color Circuit No. Function 30 OG 1540 Battery Positive Voltage 85 PK 339 Ignition 1 Voltage 86 BN/WH 436 Air Pump Relay Control 87 RD 78 Air Pump Supply Voltage

Secondary Air Injection (AIR) Solenoid Relay (NU3) Connector Part Information OEM: 12129716 Service: 15306045 4-Way F Metri-Pack 280 Series, Flexlock (GY) Pin Wire Color Circuit No. Function 30 PK 339 Ignition 1 Voltage 85 PK 339 Ignition 1 Voltage 86 PK/BK 429 Air Injection Reaction Solenoid Relay Coil Control 87 PU 421 Air Injection Reaction Solenoid Control

Throttle Actuator Control (TAC) Module Connector Part Information OEM: 15355368 Service: 15355368 20-Way F GT 150 Series Sealed (GY) Pin Wire Color Circuit No. Function 1 TN 1274 5-Volt Reference 2 PU 1272 Low Reference 3 L-BU 1162 APP Sensor 2 Signal 4 D-GN 389 Vehicle Speed Signal 5 - - Not Used 6 WH 17 Stop Lamp Switch Signal 7 OG/BK 1061 UART Serial Data Secondary 8 TN/WH 551 Ground 9-10 - - Not Used 11 D-BU 1161 APP Sensor 1 Signal 12 BN 1271 Low Reference 13 WH/BK 1164 5-Volt Reference 14-15 - - Not Used 16 TN 800 UART Serial Data Primary 17 TN/WH 551 Ground 18 PK 39 Ignition 1 Voltage 19-20 - - Not Used

DIAGNOSTIC CODE INDEX

DIAGNOSTIC CODE INDEX

Powertrain Control Module (PCM) Replacement

Service of the powertrain control module (PCM) should normally consist of either replacement of the PCM or electrically erasable programmable read only memory (EEPROM) programming. If the diagnostic procedures call for PCM replacement, inspect the PCM first to see if the replacement is the correct part. If the PCM is faulty, remove the PCM and install the new service PCM.

The new service PCM will not be programmed. You must program the new PCM. DTC P0602 indicates the EEPROM is not programmed or has malfunctioned.

Note. Do not touch the connector pins or soldered components on the circuit board in order to prevent possible electrostatic discharge (ESD) damage to the PCM.

Note. Turn the ignition OFF when installing or removing the PCM connectors and disconnecting or reconnecting the power to the PCM (battery cable, PCM pigtail, PCM fuse, jumper cables, etc.) in order to prevent internal PCM damage.

Removal Procedure

1. Using a scan tool, retrieve the percentage of remaining engine oil. Record the remaining engine oil life.
2. Disconnect the negative battery cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure (L26)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) or «Battery Negative Cable Disconnect/Connect Procedure (LY7)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.
3. Remove the left front inner fender brace. Refer to «Brace Replacement - Front Fender Upper Diagonal»(/buick/lacrosse/i-2004-2009/remont/exterior-body-panels/#body-front-end) in Body Front End.
4. Remove the air cleaner intake duct. Refer to «Air Cleaner Intake Duct Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
5. Remove the air cleaner housing cover screws (2).
6. Remove the air cleaner housing cover (1).
7. Without disconnecting the PCM electrical connectors, remove the PCM and the wiring harness from the air cleaner housing assembly (3).
8. Disconnect the PCM electrical connectors and remove the PCM (4).

Installation Procedure

1. Install the PCM to the PCM electrical connectors (4). Tighten: Tighten the connectors to 8 N.m (71 lb in).
2. Install the PCM and the wiring harness to the air cleaner housing assembly (3).
3. Install the air cleaner housing cover (1).
4. Install the air cleaner housing cover screws (2). Tighten: Tighten the screws to 4 N.m (35 lb in).
5. Install the air cleaner intake duct. Refer to «Air Cleaner Intake Duct Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
6. Install the left front inner fender brace. Refer to «Brace Replacement - Front Fender Upper Diagonal»(/buick/lacrosse/i-2004-2009/remont/exterior-body-panels/#body-front-end) in Body Front End.
7. Connect the negative battery cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure (L26)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) or «Battery Negative Cable Disconnect/Connect Procedure (LY7)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.
8. The new PCM must be programmed. Refer to «Control Module References»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#computerintegrating-systems__control-module-references) in Computer/Integrating Systems.

CKP System Variation Learn Procedure

1. Install a scan tool.
2. Monitor the PCM for DTCs with a scan tool. If other DTCs are set, except DTC P0315, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/lacrosse/i-2004-2009/remont/oem-general-information/#vehicle-dtc-information__diagnostic-trouble-code-dtc-list) for the applicable DTC.
3. With a scan tool, select the CKP variation learn procedure and perform the following: Observe fuel cut-off for applicable engine. Block drive wheels. Set parking brake. DO NOT apply brake pedal. Cycle ignition from OFF to ON. Apply and hold brake pedal for the duration of the procedure. Start and idle engine. Turn the air conditioning (A/C) OFF. The vehicle must remain in Park or Neutral. IMPORTANT: The engine should not accelerate beyond the calibrated fuel cut-off RPM value noted in step 3.1. Release the throttle immediately if the value is exceeded. 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 wide open throttle (WOT).
4. 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»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-dtc-p0220-to-dtc-p0449) . If any other DTCs set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/lacrosse/i-2004-2009/remont/oem-general-information/#vehicle-dtc-information__diagnostic-trouble-code-dtc-list) for the applicable DTC.
5. Turn OFF the ignition for 30 seconds after the learn procedure is completed successfully in order to store the CKP system variation values in the PCM memory.

Note. Use care when handling the coolant sensor. Damage to the coolant sensor will affect the operation of the fuel control system.

1. Partially drain the cooling system. Refer to «Draining and Filling Cooling System (L26 Static Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) , «Draining and Filling Cooling System (LY7 Static Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) or «Draining and Filling Cooling System (L26, LY7, GE 47716 Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) in Engine Cooling.
2. Disconnect the engine coolant temperature (ECT) sensor electrical connector.
3. Remove the ECT sensor.

Note. Use care when handling the coolant sensor. Damage to the coolant sensor will affect the operation of the fuel control system.

1. Coat the threads with sealer GM P/N 12346004 (Canadian P/N 10953480) or equivalent.
2. Install the ECT sensor. Tighten: Tighten the ECT sensor to 25 N.m (18 lb ft).
3. Connect the ECT sensor electrical connector.
4. Fill the cooling system. Refer to «Draining and Filling Cooling System (L26 Static Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) , «Draining and Filling Cooling System (LY7 Static Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) or «Draining and Filling Cooling System (L26, LY7, GE 47716 Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) in Engine Cooling.

1. Remove the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.
2. Disconnect the MAF/IAT sensor electrical connector (2).
3. Loosen the air cleaner intake duct clamps.
4. Remove the air cleaner intake duct from the air cleaner housing cover and the throttle body assembly.
5. Remove the MAF/IAT sensor from the air cleaner intake duct.

1. Install the MAF/IAT sensor to the air cleaner intake duct.
2. Install the air cleaner intake duct to the air cleaner housing cover and the throttle body assembly.
3. Tighten the air cleaner intake duct clamp screws. Tighten: Tighten the duct clamps to 3 N.m (27 lb in).
4. Connect the MAF/IAT sensor electrical connector.
5. Install the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.

Manifold Absolute Pressure (MAP) Sensor Replacement

On the L26, the manifold absolute pressure (MAP) sensor is mounted to the positive crankcase ventilation (PCV) valve cover.

1. Remove the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.
2. Disconnect the MAP sensor electrical connector.
3. Carefully release the locking tabs holding the MAP (1) sensor to the PCV valve cover (2) just enough to remove the MAP sensor.
4. Pull the MAP sensor straight out of PCV valve cover.

1. Ensure that the seal is installed on the MAP sensor and that the seal is not damaged.
2. Position and install the MAP sensor (1) to the PCV valve cover (2). Ensure that the locking tabs engage to hold the MAP sensor to the PCV valve cover.
3. Connect the MAP sensor electrical connector.
4. Install the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.

1. Remove the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.
2. Disconnect the barometric pressure (BARO) sensor electrical connector.
3. Remove the BARO sensor retainer.
4. Remove the BARO sensor.

1. Install the BARO sensor.
2. Install the BARO sensor retainer.
3. Connect the BARO sensor electrical connector.
4. Install the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.

Tools Required

J 39194 Oxygen Sensor Wrench. See Special Tools .

Note. The Heated Oxygen Sensor (HO2S) and the Oxygen Sensor use a permanently attached pigtail and connector. Do not remove this pigtail from the Heated Oxygen Sensor. Damage or the removal of the pigtail or the connector could affect the proper operation of the sensor. Take care when handling the HO2S and the O2S. Keep the in-line electrical connector and the louvered end free of grease, dirt or other contaminants. Also avoid using cleaning solvents of any type. Do not drop the HO2S or the O2S. Do not roughly handle the HO2S or the O2S.

1. Remove the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.
2. Remove the heated oxygen sensor (HO2S) retaining clip.
3. Disconnect the HO2S electrical connector (1).
4. Remove the HO2S electrical connector (1) from the fuel injector sight shield bracket.
5. Use the J 39194 to remove the HO2S (2) from the right exhaust manifold. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__special-tools) .

1. Install the HO2S (2) to the right exhaust manifold. Tighten: Use the J 39194 to tighten the HO2S to 42 N. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__special-tools) .m (31 lb ft).
2. Install the HO2S electrical connector (1) to the fuel injector sight shield bracket.
3. Connect the HO2S electrical connector (1).
4. Install the HO2S retaining clip.
5. Install the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.

J 39194 Oxygen Sensor Wrench. See Special Tools .

Note. The Heated Oxygen Sensor (HO2S) and the Oxygen Sensor use a permanently attached pigtail and connector. Do not remove this pigtail from the Heated Oxygen Sensor. Damage or the removal of the pigtail or the connector could affect the proper operation of the sensor. Take care when handling the HO2S and the O2S. Keep the in-line electrical connector and the louvered end free of grease, dirt or other contaminants. Also avoid using cleaning solvents of any type. Do not drop the HO2S or the O2S. Do not roughly handle the HO2S or the O2S.

Note. The oxygen sensor may be difficult to remove when the engine temperature is below 48°C (120°F). Excessive force may damage threads in the exhaust manifold or the exhaust pipe.

1. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/buick/lacrosse/i-2004-2009/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.
2. Remove the heated oxygen sensor (HO2S) electrical connector retaining clip from the HO2S electrical harness connector.
3. Disconnect the HO2S electrical connector from the HO2S electrical harness connector.
4. Use the J 39194 to remove the O2S from the exhaust pipe. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__special-tools) .

1. Install the O2S to the exhaust pipe. Tighten: Use the J 39194 to tighten the O2S to 42 N. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__special-tools) .m (31 lb ft).
2. Connect the HO2S electrical connector to the HO2S electrical harness connector.
3. Install the HO2S electrical connector retaining clip to the HO2S electrical harness connector.
4. Lower the vehicle.

1. Remove the left instrument panel (I/P) sound insulator. Refer to «Closeout/Insulator Panel Replacement - Left»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) .
2. Disconnect the accelerator pedal position (APP) sensor electrical connector.
3. Remove the accelerated pedal bolts (2).
4. Remove the accelerator pedal (1) from the vehicle.

1. Position the accelerator pedal (1) to the vehicle.
2. Install the accelerator pedal bolts (2). Tighten: Tighten the bolts to 5 N.m (44 lb in).
3. Connect APP sensor electrical connector.
4. Install the left I/P sound insulator. Refer to «Closeout/Insulator Panel Replacement - Left»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) .

1. Partially drain the cooling system. Refer to «Draining and Filling Cooling System (L26 Static Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) , «Draining and Filling Cooling System (LY7 Static Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) or «Draining and Filling Cooling System (L26, LY7, GE 47716 Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) in Engine Cooling.
2. Remove the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.
3. Remove the air cleaner intake duct. Refer to «Air Cleaner Intake Duct Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction-2-of-2) .
4. Disconnect the throttle body electrical connector.
5. Remove the throttle body nuts (4) and the bolts (5).
6. Remove the throttle body assembly (1).
7. Clean the throttle body gasket mating surfaces.

1. Install the new gasket.
2. Install the throttle body assembly (1).
3. Install the throttle body bolts (5) and the nuts (4). Tighten: Tighten the bolts and the nuts to 10 N.m (89 lb in).
4. Connect the throttle body electrical connector.
5. Install the air cleaner intake duct. Refer to «Air Cleaner Intake Duct Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction-2-of-2) .
6. Install the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.
7. Fill the cooling system. Refer to «Draining and Filling Cooling System (L26 Static Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) , «Draining and Filling Cooling System (LY7 Static Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) or «Draining and Filling Cooling System (L26, LY7, GE 47716 Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) in Engine Cooling.

1. Disconnect the air intake ducts from the throttle body.
2. Inspect the throttle body bore and the throttle valve plate for any deposits. It is necessary to open the throttle valve in order to inspect all of the surfaces.
3. Clean the throttle body bore and the throttle valve plate by using a clean shop towel with Top Engine Cleaner, GM P/N 1052626 (Canadian P/N 993026) or AC-Delco Carburetor Tune-Up Conditioner, P/N X66-P or an equivalent product.

1. Connect the air intake ducts to the throttle body.
2. Inspect for air leaks.

J 34730-1A Fuel Pressure Gage

Fuel Pressure Relief Procedure

1. Disconnect the negative battery cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure (L26)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) or «Battery Negative Cable Disconnect/Connect Procedure (LY7)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.
2. Remove the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.
3. Loosen the fuel filler cap to relieve tank vapor pressure.
4. Connect the J 34730-1A to the fuel pressure connection. Wrap a shop towel around the fuel pressure connection while connecting the fuel pressure gauge in order to avoid spillage.
5. Install the bleed hose into an approved container and open the valve to bleed the system pressure. The fuel connection is now safe for servicing.
6. Drain any fuel remaining in the fuel pressure gage into an approved container.

J 34730-1A Fuel Pressure Gage

1. Remove the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.
2. Install the J 34730-1A to the fuel pressure service connection, located on the fuel rail.
3. Turn ON the ignition.
4. Place the bleed hose of the fuel pressure gage into an approved gasoline container.
5. Open the bleed valve on the fuel pressure gage in order to bleed the air from the fuel pressure gage.
6. Command the fuel pump ON with a scan tool.
7. Close the bleed valve on the fuel pressure gage.
8. Inspect for fuel leaks.

1. Place the fuel pressure gage bleed hose into an approved container. Open the bleed valve in order to bleed the fuel system pressure.
2. Place a shop towel under the fuel pressure gage in order to catch any remaining fuel spillage.
3. Remove the fuel pressure gage from the fuel pressure connection.
4. Drain any fuel remaining in the fuel pressure gage into an approved container.
5. Inspect for leaks using the following procedure: Turn ON the ignition, with the engine OFF for 2 seconds. Turn OFF the ignition for 10 seconds. Turn ON the ignition, with the engine OFF. Inspect for fuel leaks.
6. Install the cap on the fuel pressure connection.
7. Install the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.

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

Note. Refer to COVER AND PLUG OPENINGS NOTICE in Cautions and Notices.

1. Relieve the fuel system pressure. Refer to «Fuel Pressure Relief Procedure»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__fuel-pressure-relief-procedure) .
2. Lift and remove the fuel line quick connect fitting retainer.
3. Grasp both sides of the fitting. Twist the female connector 1/4 turn in each direction to loosen any dirt within the fitting.
4. Blow dirt out of the fitting using compressed air.
5. Insert the J 37088-A into the female connector (1), then push inward to release the locking tabs. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__special-tools) .
6. Pull the connection apart.
7. Using a clean shop towel, wipe off the male pipe end.
8. Inspect both ends of the fitting for dirt and burrs. Clean or replace the components as required.

1. Apply a few drops of clean engine oil to the male pipe end.
2. Push the female connector (1) onto the fuel rail pipe.
3. Once installed, pull on both sides of the fitting to ensure that the connection is secure.
4. Install the fuel line quick connect fitting retainer.
5. Tighten the fuel filler cap.
6. Connect the negative battery cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure (L26)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) or «Battery Negative Cable Disconnect/Connect Procedure (LY7)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.
7. Inspect for leaks. Turn ON the ignition for 2 seconds. Turn OFF the ignition for 10 seconds. Turn ON the ignition. Inspect for fuel leaks.

Note. Refer to COVER AND PLUG OPENINGS NOTICE in Cautions and Notices.

1. Relieve the fuel system pressure. Refer to «Fuel Pressure Relief Procedure»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__fuel-pressure-relief-procedure) .
2. Grasp both sides of the quick-connect fitting. Twist quick-connect fitting 1/4 turn in each direction to loosen any dirt within fitting.
3. Use compressed air to blow out dirt from the quick-connect fittings at both ends.
4. Squeeze plastic tabs of male end connector.
5. Pull the connection apart. Repeat the step for the other fitting.
6. Wipe off the male pipe end using a clean shop towel.
7. Clean or replace the components/assemblies, as required.

1. Apply a few drops of clean oil to the male pipe end.
2. Push both sides of the quick-connect fitting together in order to cause the retaining tabs/fingers to snap into place.
3. Pull on both sides of the quick connect fitting in order to ensure that the connection is secure.
4. Tighten the fuel filler cap.
5. Connect negative battery cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure (L26)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) or «Battery Negative Cable Disconnect/Connect Procedure (LY7)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.
6. Inspect for fuel leaks. Turn ON the ignition for 2 seconds. Turn OFF the ignition for 10 seconds. Turn ON the ignition. Inspect for fuel leaks.

Fuel Tank Draining Procedure

Note. Do not drain fuel through the fuel tank filler pipe in order to prevent damage to the fuel tank filler pipe check-ball.

1. Relieve the fuel system fuel pressure. Refer to «Fuel Pressure Relief Procedure»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__fuel-pressure-relief-procedure) .
2. Remove the fuel sender assembly. Refer to «Fuel Sender Assembly Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
3. Use a hand operated fuel pump device in order to drain the fuel through the fuel sender access panel.
4. Install the fuel sender assembly. Refer to «Fuel Sender Assembly Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
5. Remove the fuel fill cap.
6. Add fuel and install the fuel fill cap.
7. Connect the negative battery cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure (L26)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) or «Battery Negative Cable Disconnect/Connect Procedure (LY7)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.
8. Inspect for leaks. Turn ON the ignition for 2 seconds. Turn OFF the ignition for 10 seconds. Turn ON the ignition. Inspect for fuel leaks.
9. Install fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.

1. Relieve the fuel system fuel pressure. Refer to «Fuel Pressure Relief Procedure»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__fuel-pressure-relief-procedure) .
2. Drain the fuel tank. Refer to «Fuel Tank Draining Procedure»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__fuel-tank-draining-procedure) .
3. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/buick/lacrosse/i-2004-2009/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.
4. Loosen the fuel filler hose clamp (1) at the fuel tank (3).
5. Remove the fuel tank filler hose from the fuel tank.
6. Disconnect the fuel feed, the fuel return and the evaporative emission (EVAP) pipes at the fuel filter area. Refer to «Quick Connect Fitting(s) Service (Plastic Collar)»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
7. Support the exhaust system.
8. Remove the rubber exhaust pipe hangers in order to allow the exhaust system to drop slightly.
9. Separate the 2 halves of the EVAP fresh air hose at the splice.
10. Remove the fuel tank shield push pins (2).
11. Remove the fuel tank shield (3).
12. Support the fuel tank with a suitable jack.
13. Remove the fuel tank strap bolts (2).
14. Remove the fuel tank from the vehicle.
15. Place the fuel tank in a suitable work area.
16. Remove the fuel feed, the fuel return and the EVAP pipe assemblies and the insulator clips from the fuel tank.
17. Remove the EVAP canister from the fuel tank.
18. Remove the insulator pads from the fuel tank. Note the location of the insulator pads for installation.

1. Install the insulator pads to the fuel tank.
2. Install the EVAP canister to the fuel tank.
3. Install the fuel feed, the fuel return and the EVAP pipe assemblies and the insulator clips.
4. Install the fuel tank to a suitable jack.
5. Raise the fuel tank (1) to the original position.
6. Install the fuel tank retaining strap bolts (2). Tighten: Tighten the bolts to 48 N.m (35 lb ft).
7. Remove the jack from the fuel tank.
8. Position the fuel tank shield (3) to the fuel tank (1).
9. Install the push pins (2).
10. Install the 2 parts of the EVAP fresh air hose at the splice.
11. Connect the EVAP pipe, the fuel feed and the fuel return pipes at the front of the fuel tank. Refer to «Quick Connect Fitting(s) Service (Plastic Collar)»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
12. Install the fuel tank filler hose to the fuel tank.
13. Fully seat the filler hose (4) on the fuel tank port (2).
14. Ensure that the fuel tank filler pipe hose clamp (1) is properly located on the tank port between the bead (5) and the tank (3). Tighten: Tighten the hose clamp to 2.5 N.m (22 lb in).
15. Raise the exhaust system to the original position.
16. Install the exhaust system to the exhaust pipe hangers.
17. Lower the vehicle.
18. Install the fuel sender assembly. Refer to «Fuel Sender Assembly Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
19. Add fuel and install the fuel fill cap.
20. Connect the negative battery cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure (L26)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) or «Battery Negative Cable Disconnect/Connect Procedure (LY7)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.
21. Inspect the fuel system for leaks by performing the following steps: Turn ON the ignition for 2 seconds. Turn OFF the ignition for 10 seconds. Turn ON the ignition. Inspect for fuel leaks.
22. Install fuel injection sight shield. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.

1. Disconnect the negative battery cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure (L26)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) or «Battery Negative Cable Disconnect/Connect Procedure (LY7)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) .
2. Remove the fuel tank assembly. Refer to «Fuel Tank Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
3. Disconnect the fuel tank pressure sensor electrical connector.
4. Remove the fuel tank pressure sensor (7) from the fuel sender assembly (1).

1. Install the new fuel tank pressure sensor (7) to the fuel sender assembly (1).
2. Connect the fuel tank pressure sensor electrical connector.
3. Install the fuel sender access panel.
4. Install the fuel sender access panel nuts. Tighten: Tighten the nuts to 10 N.m (89 lb in).
5. Install the fuel tank. Refer to in «Fuel Tank Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
6. Connect the negative battery cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure (L26)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) or «Battery Negative Cable Disconnect/Connect Procedure (LY7)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) .

1. Remove the fuel sender assembly. Refer to «Fuel Sender Assembly Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
2. Disconnect the fuel level sensor electrical connector.
3. Remove the fuel level sensor (5) from the fuel sender assembly.

1. Install the fuel level sensor (5) to the fuel sender assembly.
2. Connect the fuel level sensor electrical connector.
3. Install the fuel sender assembly. Refer to «Fuel Sender Assembly Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .

1. Remove the fuel sender assembly. Refer to «Fuel Sender Assembly Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
2. Note the strainer (3) position for future reference.
3. Support the reservoir with one hand. Grasp the strainer with the other hand.
4. Use a screwdriver to pry the strainer ferrule off the reservoir.
5. Discard the strainer.

1. Install the new strainer (4) to the reservoir.
2. Support the reservoir with one hand. Grasp the strainer with the other hand. Twist the strainer into position.
3. Install the fuel sender assembly. Refer to «Fuel Sender Assembly Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .

Note. Cap the fittings and plug the holes when servicing the fuel system in order to prevent dirt and other contaminants from entering the open pipes and passages.

1. Drain the fuel tank. Refer to «Fuel Tank Draining Procedure»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__fuel-tank-draining-procedure) .
2. Remove the fuel filler cap.
3. Remove the fuel filler pipe screws from the fuel filler pocket.
4. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/buick/lacrosse/i-2004-2009/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.
5. Loosen the fuel filler hose clamp (1) at the fuel filler pipe (2).
6. Remove the fuel filler pipe screw from the under body.
7. Remove the fuel filler pipe.

1. Install the fuel filler pipe.
2. Install the fuel tank filler pipe screw to the under body. Tighten: Tighten the screw to 13 N.m (115 lb in).
3. Install the filler hose (4) to the fuel fill pipe (2). Inspect and ensure the filler hose (4) is fully seated on the fuel tank port and the fuel filler pipe (2).
4. Ensure the clamp (1) is properly located on the tank port between the bead (5) and the pipe (3). Tighten: Tighten the fuel tank filler pipe hose clamp to 2.5 N.m (22 lb in).
5. Lower the vehicle.
6. Install the fuel filler pipe screws to the fuel filler pipe access panel. Tighten: Tighten the screws to 2.5 N.m (22 lb in).
7. Add fuel and install the fuel fill cap.

J 45722 Fuel Sender Lock Ring Wrench

1. Remove the fuel tank. Refer to «Fuel Tank Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
2. Disconnect the fuel sender module electrical connectors.
3. Disconnect the fuel pipes from the fuel sender. Refer to «Quick Connect Fitting(s) Service (Plastic Collar)»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
4. Use the J 45722 and a long breaker-bar in order to unlock the fuel sender lock ring. Turn the fuel sender lock ring in a counterclockwise direction.
5. Remove the fuel sender lock ring (1) and the fuel sender (2) from the fuel tank.
6. Remove and discard the fuel sender seal (3).
7. Remove the fuel level sensor from the fuel sender module. Refer to «Fuel Tank Pressure Sensor Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
8. Place the lock ring on a flat surface. Measure the clearance between to lock ring and the flat surface using a feeler gage at 7 points.
9. If the warpage is less than 0.41 mm (0.016 in), the lock ring does not require replacement.
10. If the warpage is greater than 0.41 mm (0.016 in), the lock ring must be replaced.

1. Install the fuel level sensor to the fuel sender module. Refer to «Fuel Tank Pressure Sensor Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
2. Clean the fuel sender sealing flange.
3. Install the NEW fuel sender seal (3) to the fuel tank seal groove.
4. Install the fuel sender (2) and the fuel sender lock ring (1).
5. Use the J 45722 in order to install the fuel sender lock ring. Turn the fuel sender lock ring in a clockwise direction.
6. Install the fuel pipes to the fuel sender. Refer to «Quick Connect Fitting(s) Service (Plastic Collar)»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
7. Install the fuel sender sensor electrical connectors.
8. Install the fuel tank. Refer to «Fuel Tank Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .

Note. Refer to COVER AND PLUG OPENINGS NOTICE in Cautions and Notices.

1. Remove the fuel tank. Refer to «Fuel Tank Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
2. Note the position of the fuel, the evaporative emission (EVAP) pipes and the attaching hardware for installation.
3. Disconnect the fuel feed (2), the fuel return (2) and the EVAP pipe quick-connect fittings at the fuel sender assembly. Refer to «Quick Connect Fitting(s) Service (Plastic Collar)»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
4. Cap the fuel sender fuel pipes and the in-pipe fuel filter pipes as needed to stop any fuel leakage.
5. Remove the fuel feed, the fuel return and the EVAP pipe attaching hardware.
6. Remove the fuel feed (2), the fuel return (2) and the EVAP pipes from the fuel tank.

Note. Refer to FUEL SYSTEM GROUND NOTICE in Cautions and Notices.

Note. Secure the fuel pipes to the frame in order to prevent chafing. Maintain a minimum of 13 mm (1/2 inch) clearance around a pipe in order to prevent contact and chafing. Maintain a minimum of 19 mm (3/4 inch) around any moving part. Do not allow the fuel pipes to come into contact with the fuel tank or underbody.

1. Install the new fuel feed (2), the fuel return (2) and the EVAP pipes to the fuel tank.
2. Install the fuel feed, the fuel return and the EVAP pipe attaching hardware.
3. Remove the caps from the in-pipe fuel filter pipes and the fuel sender fuel pipes.
4. Connect the fuel feed (2), the fuel return (2) and the EVAP pipe quick-connect fittings at the fuel sender assembly. Refer to «Quick Connect Fitting(s) Service (Plastic Collar)»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
5. Ensure that all of the fuel pipe bundle clips and fasteners are properly installed.
6. Install the fuel tank. Refer to «Fuel Tank Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .

Fuel System Cleaning

Note. Refer to COVER AND PLUG OPENINGS NOTICE in Cautions and Notices.

1. Remove the fuel tank. Refer to «Fuel Tank Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
2. Inspect the fuel pump inlet for dirt and debris. If dirt and debris are found, replace the fuel pump.
3. Flush fuel tank with hot water.
4. Pour the water out of the fuel sender assembly opening in the fuel tank. Rock the fuel tank in order to ensure that the removal of the water from the fuel tank is complete.
5. Allow tank to dry completely before reassembly.
6. Install the fuel sender assembly. Refer to «Fuel Sender Assembly Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
7. Install the fuel tank. Refer to «Fuel Tank Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .

Note. Refer to FUEL RAIL NOTICE in Cautions and Notices.

Note. Refer to COVER AND PLUG OPENINGS NOTICE in Cautions and Notices.

1. Relieve the fuel pressure from the fuel system. Refer to «Fuel Pressure Relief Procedure»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__fuel-pressure-relief-procedure) .
2. Clean the fuel rail assembly and the fuel feed pipe.
3. Disconnect the fuel feed pipe (1) from the fuel rail. Refer to «Quick Connect Fitting(s) Service (Metal Collar)»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
4. Remove the spark plug wires from the fuel rail.
5. Disconnect and reposition the spark plug wires from the ignition control module.
6. Disconnect the fuel injector electrical connectors.
7. Remove the fuel rail hold-down nuts (2).
8. Remove the fuel rail (1) with the fuel injectors (3) with equal force on both sides of the fuel rail.

Note. Refer to FUEL RAIL NOTICE in Cautions and Notices.

1. The O-rings must be replaced on all components that are serviced.
2. Lightly oil the fuel injector O-rings with clean engine oil.
3. Place the fuel rail (1) with the fuel injectors (3) on the intake manifold.
4. Seat the fuel injectors (3) by HAND.
5. Install the fuel rail hold-down nuts (2). Tighten: Tighten the nuts to 10 N.m (89 lb in).
6. Connect the fuel injector electrical connectors.
7. Reposition the spark plug wires to the fuel rail.
8. Connect the spark plug wires to the ignition control module.
9. Connect the fuel feed pipe (1) to the fuel rail. Refer to «Quick Connect Fitting(s) Service (Metal Collar)»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
10. Tighten the fuel fill cap.
11. Connect the negative battery cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure (L26)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) or «Battery Negative Cable Disconnect/Connect Procedure (LY7)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.
12. Inspect for leaks. Turn ON the ignition for 2 seconds. Turn OFF the ignition for 10 seconds. Turn ON the ignition. Inspect for fuel leaks.
13. Install the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.

1. Relieve the fuel pressure. Refer to «Fuel Pressure Relief Procedure»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__fuel-pressure-relief-procedure) .
2. Clean any dirt from the fuel pressure regulator retaining ring.
3. Remove the vacuum line from the pressure regulator.
4. Remove the snap ring (7).
5. Using a shop towel to catch any spilled fuel, lift and twist the fuel pressure regulator in order to remove the fuel pressure regulator (6) from the fuel pressure regulator housing (1).
6. Remove the regulator O-ring small (2).
7. Remove the regulator O-ring large (4).
8. Remove the regulator O-ring back up (5).
9. Cover the fuel pressure regulator housing (1) to prevent contamination from entering the fuel system.

Note. Do not use compressed air in order to test or clean a fuel pressure regulator as damage to the fuel pressure regulator may result. Clean the fuel pressure regulator filter screen with gasoline if necessary. Do not immerse the fuel pressure regulator in a solvent bath in order to prevent damage to the fuel pressure regulator.

1. Install the new O-rings on the fuel pressure regulator (6), if a new fuel pressure regulator is not being installed. Lubricate the O-rings lightly with clean engine oil.
2. Install the regulator back up O-ring (5).
3. Install the regulator O-ring large (4).
4. Install the regulator O-ring small (2).
5. Install the fuel pressure regulator (6) in the fuel pressure regulator housing (1).
6. Install the snap ring (7).
7. Connect the vacuum line to the fuel pressure regulator.
8. Tighten the fuel fill cap.
9. Connect the negative battery cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure (L26)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) or «Battery Negative Cable Disconnect/Connect Procedure (LY7)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.
10. Inspect for leaks. Turn ON the ignition for 2 seconds. Turn OFF the ignition for 10 seconds. Turn ON the ignition. Inspect for fuel leaks.
11. Install the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.

1. J 37287 Fuel Line Shut-Off Adapters
2. J 35800-A Fuel Injector Cleaner. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__special-tools) .
3. J 42873-1 3/8 Fuel Line Shut-Off Valve. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__special-tools) .
4. J 42873-2 5/16 Return Pipe Shut-Off Valve. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__special-tools) .
5. J 42964-1 3/8 Fuel Pipe Shut-Off Valve. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__special-tools) .
6. J 42964-2 5/16 Fuel Pipe Shut-Off Valve. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__special-tools) .

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.

Cleaning Procedure

1. Obtain J 35800-A (2). See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__special-tools) .
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 . See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__special-tools) .
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 . See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__special-tools) .
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»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__special-tools) .
8. Connect the J 35800-A to the vehicle fuel rail. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__special-tools) .
9. Pressurize the J 35800-A to 510 kPa (75 psi). See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__special-tools) .
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. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__special-tools) .
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 , J 42873-2 and reconnect the vehicle fuel feed and return lines. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__special-tools) .
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.

Note. Use care in removing the fuel injectors in order to prevent damage to the fuel injector electrical connector pins or the fuel injector nozzles. Do not immerse the fuel injector in any type of cleaner. The fuel injector is an electrical component and may be damaged by this cleaning method.

1. Remove the fuel rail. Refer to «Fuel Rail Assembly Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
2. Remove the fuel injector retaining clip (1).
3. Remove the fuel injector (3).
4. Remove the fuel injector upper O-ring (2).
5. Remove the fuel injector lower O-ring (4).

Scheme 84

The fuel injector assembly (1) is stamped with a part number identification (2), a manufacturing date (3), a week code (1) and a production plant number (4).

1. Coat all new O-rings with clean engine oil before installing
2. Install the fuel injector lower O-ring (4).
3. Install the fuel injector upper O-ring (2).
4. Install the fuel injector (3) to the fuel rail.
5. Install the fuel injector retaining clip (1).
6. Install the fuel rail. Refer to «Fuel Rail Assembly Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .

1. Remove the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.
2. Disconnect the EVAP canister purge valve purge pipe (2).
3. Disconnect the EVAP canister purge valve electrical connector.
4. Remove the EVAP purge valve bolt (2).
5. Remove the EVAP purge valve (3).

1. Install the EVAP purge valve (3).
2. Install the EVAP purge valve bolt (2). Tighten: Tighten the bolt to 12 N.m (106 lb in).
3. Connect the EVAP canister purge valve electrical connector.
4. Connect the EVAP canister purge valve purge pipe (2).
5. Install the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.

1. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/buick/lacrosse/i-2004-2009/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.
2. Disconnect the evaporative emission (EVAP) vent valve electrical connector (1).
3. Remove the EVAP vent valve bracket bolt.
4. Remove the vent hose (4) from the EVAP vent valve.
5. Remove the EVAP vent valve from the bracket (2).

1. Install the EVAP vent valve to the bracket (2).
2. Install the vent hose (4) to the EVAP vent valve.
3. Install the EVAP vent valve and the bracket.
4. Install the EVAP vent valve bracket bolt. Tighten: Tighten the bolt to 10 N.m (89 lb in).
5. Connect the EVAP vent valve electrical connector (1).
6. Lower the vehicle.

1. Remove the fuel tank. Refer to «Fuel Tank Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
2. Disconnect the evaporative emission (EVAP) vapor pipe (7) from the EVAP canister (1), the fill limiter vent valve and the fuel sender assembly.
3. Remove the EVAP vapor pipe.

1. Position the EVAP vapor pipe on the fuel tank.
2. Connect the EVAP vapor pipe (7) to the EVAP canister (1), the fill limiter vent valve and the fuel sender assembly.
3. Install the fuel tank. Refer to «Fuel Tank Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .

1. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/buick/lacrosse/i-2004-2009/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.
2. Disconnect the evaporative emission (EVAP) purge pipe connector at the fuel filter area. Refer to «Quick Connect Fitting(s) Service (Plastic Collar)»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
3. Disconnect the EVAP purge pipe (8) from the EVAP canister (1). Refer to «Quick Connect Fitting(s) Service (Plastic Collar)»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
4. Remove the EVAP purge pipe (8).

1. Connect the EVAP purge pipe (8) to the EVAP canister. Refer to «Quick Connect Fitting(s) Service (Plastic Collar)»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
2. Connect the EVAP purge pipe at the fuel filter area. Refer to «Quick Connect Fitting(s) Service (Plastic Collar)»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
3. Lower the vehicle.

1. Remove the fuel hose/pipe bundle. Refer to «Evaporative Emission (EVAP) Hoses/Pipes Replacement - Engine/Chassis»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
2. Remove the evaporative emission (EVAP) purge pipe from the fuel bundle.

1. Install the EVAP purge pipe into the fuel bundle.
2. Install the fuel hose/pipe bundle. Refer to «Evaporative Emission (EVAP) Hoses/Pipes Replacement - Engine/Chassis»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .

1. Remove the fuel tank. Refer to «Fuel Tank Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
2. Disconnect the EVAP vent hose (6), the EVAP purge pipe (8) and the EVAP vapor pipe (7) from the EVAP canister (1). Refer to «Quick Connect Fitting(s) Service (Plastic Collar)»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
3. Release the EVAP canister retaining strap.
4. Remove the EVAP canister (1) from the fuel tank.

1. Position the EVAP canister (1) on the fuel tank.
2. Install the new EVAP canister retaining strap.
3. Connect the EVAP vent hose (6), the EVAP purge pipe (8) and the EVAP vapor pipe (7) to the EVAP canister (1). Refer to «Quick Connect Fitting(s) Service (Plastic Collar)»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
4. Install the fuel tank. Refer to «Fuel Tank Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .

1. Disconnect the negative battery cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure (L26)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) or «Battery Negative Cable Disconnect/Connect Procedure (LY7)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.
2. Disconnect the spark plug wires from the ignition coil.
3. Remove the ignition coil screws (1).
4. Remove the ignition coil (2).

1. Install the ignition coil (2).
2. Install the ignition coil screws (1). Tighten: Tighten the screws to 4.5 N.m (40 lb in).
3. Connect the spark plug wires.
4. Connect the negative battery cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure (L26)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) or «Battery Negative Cable Disconnect/Connect Procedure (LY7)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.

1. Disconnect the negative battery cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure (L26)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) or «Battery Negative Cable Disconnect/Connect Procedure (LY7)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.
2. Remove the 14-way electrical connector from the ignition control module (ICM).
3. Disconnect the spark plug wires from the coil assemblies. Before removing the wires, note the position of the wires.
4. Remove the ICM nuts (2).
5. Remove the ICM (1) from the bracket.
6. Remove the ignition coil screws (1).
7. Remove the ignition coils (2) from the ICM (3).

1. Install the ignition coils (2) to the ICM (3).
2. Install the ignition coil screws (1). Tighten: Tighten the screws to 4.5 N.m (40 lb in).
3. Install the ICM (1) to the bracket.
4. Install the ICM nuts (2). Tighten: Tighten the nuts to 10 N.m (89 lb in).
5. Connect the spark plug wires to the ignition coils.
6. Install the 14-way electrical connector to the ICM. Tighten: Tighten the screw to 2.1 N.m (19 lb in).
7. Connect the negative battery cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure (L26)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) or «Battery Negative Cable Disconnect/Connect Procedure (LY7)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.

Spark Plug Wire Inspection

Spark plug wire integrity is vital for proper engine operation. A thorough inspection will be necessary to accurately identify conditions that may affect engine operation. Refer to the list below for items to be inspected.

1. Inspect for correct routing of the spark plug wires. Improper routing may cause cross-firing.
2. Inspect each wire for any signs of cracks or splits in the wire.
3. Inspect each boot for the following conditions: Tearing Piercing Arcing Carbon tracking Corroded terminal

If corrosion, carbon tracking or arcing are indicated on a spark plug wire boot or terminal both the wire and the component connected to the wire should be replaced.

J 38491 Spark Plug Boot Removal Tool. See Special Tools .

1. Remove the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.
2. Remove the spark plug wires (2, 4, 6) from the spark plugs at the rear of the engine using the following steps: Note the position of the spark plug wires before removing the wires. Twist the spark plug boot 1/2 turn before removing the boot. Gently pry the heat shield up from spark plugs using the J 38491 . See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__special-tools) . Remove the spark plug wire from the spark plugs at rear of the engine.
3. Remove the spark plug wires (1, 3, 5) from the spark plugs at the front of the engine using the following steps: Note the position of the spark plug wires before removing the wires. Twist the spark plug boot 1/2 turn before removing the boot. Gently pry the heat shield up from spark plugs using the J 38491 . See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__special-tools) . Remove the spark plug wires form the spark plugs at the front of the engine.
4. Remove the spark plug wires from the ignition coils.
5. Remove the spark plug wire retaining clips from the rear, front and top of the engine.
6. Remove the spark plug wires from the engine.
7. When replacing the spark plug wires transfer any of the following: Boot heat shields Spark plug wire conduit Spark plug wire retaining clips

1. Position the spark plug wires to the engine.
2. Install the spark plug wire retaining clips from the rear, front and top of the engine.
3. Install the spark plug wires to the ignition coil in the proper position.
4. Install the spark plug wires (1, 3, 5) to the spark plugs in the proper position at the front of the engine.
5. Install the spark plug wires (2, 4, 6) to the spark plugs in the proper position at the rear of the engine.
6. Install the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.

Spark Plug Usage

1. Ensure that the correct spark plug is installed. An incorrect spark plug causes driveability conditions. Refer to the appropriate parts catalog 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 «Engine Mechanical Specifications»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l__engine-mechanical-specifications) in Engine Mechanical - 3.8L. An excessively wide electrode gap can prevent correct spark plug operation. Inspect for the correct spark plug torque. Refer to «Fastener Tightening Specifications»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__fastener-tightening-specifications) . 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.

1. Remove the spark plug wires from the spark plugs. Refer to «Spark Plug Wire Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
2. Remove the spark plugs from the engine.

1. Measure the spark plug gap on the spark plugs to be installed. Compare the measurement to the gap specifications. Refer to «Ignition System Specifications»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__ignition-system-specifications) . Correct as necessary.
2. Install the spark plugs to the engine. Tighten: If installing the spark plugs to a new cylinder head tighten the plugs to 27 N.m (20 lb ft). If installing the spark plugs to an existing cylinder head tighten the plugs to 15 N.m (11 lb ft).
3. Connect the spark plug wires to the spark plugs. Refer to «Spark Plug Wire Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .

1. Disconnect the negative battery cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure (L26)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) or «Battery Negative Cable Disconnect/Connect Procedure (LY7)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.
2. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/buick/lacrosse/i-2004-2009/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.
3. Remove the crankshaft harmonic balancer. Refer to «Crankshaft Balancer Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.
4. Disconnect the crankshaft position (CKP) sensor electrical connector.
5. Remove the CKP sensor shield (1). DO NOT use a pry bar.
6. Remove the CKP sensor studs.
7. Remove the CKP sensor.

1. Install the CKP sensor.
2. Install the CKP sensor studs. Tighten: Tighten the studs to 30 N.m (22 lb ft).
3. Install the CKP sensor shield (1).
4. Connect the CKP sensor electrical connector.
5. Install the crankshaft harmonic balancer. Refer to «Crankshaft Balancer Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.
6. Lower the vehicle.
7. Connect the negative battery cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure (L26)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) or «Battery Negative Cable Disconnect/Connect Procedure (LY7)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.
8. Perform the crankshaft position system variation learn procedure. Refer to «CKP System Variation Learn Procedure»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2__ckp-system-variation-learn-procedure) .

1. Remove the coolant recovery reservoir. Refer to «Coolant Recovery Reservoir Replacement»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) in Engine Cooling.
2. Remove the drive belt. Refer to «Drive Belt Replacement (L26)»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.
3. Disconnect the electrical connector (2) from the camshaft position sensor (1).
4. Remove the camshaft position sensor bolt.
5. Remove the camshaft position sensor from the engine front cover.

1. Install the camshaft position sensor to the engine front cover.
2. Install the camshaft position sensor bolt. Tighten: Tighten the bolt to 10 N.m (89 lb in).
3. Connect the electrical connector (2) to the camshaft position sensor (1).
4. Install the drive belt. Refer to «Drive Belt Replacement (L26)»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.
5. Install the coolant recovery reservoir. Refer to «Coolant Recovery Reservoir Replacement»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) in Engine Cooling.

1. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/buick/lacrosse/i-2004-2009/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.
2. Drain the cooling system. Refer to «Draining and Filling Cooling System (L26 Static Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) , «Draining and Filling Cooling System (LY7 Static Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) or «Draining and Filling Cooling System (L26, LY7, GE 47716 Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) in Engine Cooling.
3. Disconnect the knock sensor electrical connector (2).
4. Remove the knock sensor (1).

1. Install the knock sensor (1). Tighten: Tighten the knock sensor to 19 N.m (14 lb ft).
2. Connect the knock sensor electrical connector (2).
3. Lower the vehicle.
4. Fill the cooling system. Refer to «Draining and Filling Cooling System (L26 Static Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) , «Draining and Filling Cooling System (LY7 Static Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) or «Draining and Filling Cooling System (L26, LY7, GE 47716 Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) in Engine Cooling.

1. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/buick/lacrosse/i-2004-2009/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) .
2. Drain the cooling system. Refer to «Draining and Filling Cooling System (L26 Static Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) , «Draining and Filling Cooling System (LY7 Static Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) or «Draining and Filling Cooling System (L26, LY7, GE 47716 Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) .
3. Disconnect the knock sensor electrical connector (3) from the knock sensor.
4. Remove the knock sensor (4).

Note. Refer to Fastener Notice .

1. Install the knock sensor (4). Tighten: Tighten the knock sensor to 19 N.m (14 lb ft).
2. Connect the knock sensor electrical connector.
3. Lower the vehicle.
4. Fill the cooling system. Refer to «Draining and Filling Cooling System (L26 Static Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) , «Draining and Filling Cooling System (LY7 Static Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) or «Draining and Filling Cooling System (L26, LY7, GE 47716 Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) .

1. Loosen and lower the secondary air injection (AIR) outlet hose pinch clamp.
2. Remove the AIR inlet hose from the AIR pump (2).
3. Disconnect the AIR pump electrical connector.
4. Remove the AIR pump (2).

1. Install the lower AIR pump bolts/nuts.
2. Install the upper AIR pump. Tighten: Tighten the upper and lower AIR pump to cradle bolts to 9 N.m (80 lb in).
3. Reconnect the AIR pump electrical connector.
4. Install the AIR outlet hose and pinch clamp to the AIR pump (2).
5. Install the AIR inlet hose to the AIR pump (2).

1. Remove the secondary air injection (AIR) shut-off valve outlet pipe/hose and shut-off valve assembly. Refer to «Secondary Air Injection (AIR) Shut-Off Valve Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
2. Remove the outlet pipe from the shut-off valve.

1. Install the outlet pipe to the shut-off valve.
2. Install the AIR shut-off valve outlet pipe/hose and shut-off valve assembly. Refer to «Secondary Air Injection (AIR) Shut-Off Valve Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .

1. Reposition the pinch clamp (1) from the valve end of the hose.
2. Disconnect the electrical connector from the shut-off valve.
3. Remove the secondary air injection (AIR) pipe fasteners (3).
4. Remove the fastener (2) that secures the valve (1) to the bracket (5).
5. Remove the valve and pipe assembly (1) from the vehicle.

1. Install the valve and pipe assembly to the AIR hose.
2. Install the fastener (2) that retains the valve (1) to the bracket (5). Tighten: Tighten the mounting bolt to 9 N.m (80 lb in).
3. Install the AIR pipe fasteners. Tighten: Tighten the mounting bolts to 9 N.m (80 lb in).
4. Install the pinch clamp (1) back into position.
5. Connect the electrical connector to the shut-off valve.

1. Disconnect the exhaust gas recirculation (EGR) valve electrical connector.
2. Remove the EGR valve nuts (1).
3. Remove the EGR valve (2).
4. Remove the gasket (3) from the EGR valve adapter.
5. Clean the EGR valve gasket mating surfaces.

1. Install a new EGR valve gasket (3).
2. Install the EGR valve (2).
3. Install the EGR valve nuts (1). Tighten: Tighten the nuts to 25 N.m (18 lb ft).
4. Connect the EGR valve electrical connector.

1. Remove the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.
2. Remove the heated oxygen sensor (HO2S). Refer to «Heated Oxygen Sensor Replacement - Position 1»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
3. Remove the exhaust manifold heat shield bolts (2).
4. Remove the exhaust manifold heat shield.
5. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/buick/lacrosse/i-2004-2009/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.
6. Remove the exhaust gas recirculation (EGR) valve inlet adapter pipe mounting bolt from the exhaust manifold.
7. Lower the vehicle.
8. Remove the EGR valve. Refer to «Exhaust Gas Recirculation (EGR) Valve Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
9. Remove the EGR valve outlet pipe. Refer to «Exhaust Gas Recirculation (EGR) Outlet Pipe Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
10. Remove the EGR valve inlet adapter pipe bolts (2).
11. Remove the EGR valve inlet adapter pipe (1).

1. Install the EGR valve inlet adapter pipe (1).
2. Install the EGR valve inlet adapter pipe bolts (2). Tighten: Tighten the bolts to 50 N.m (37 lb ft).
3. Raise the vehicle.
4. Install the EGR valve inlet adapter pipe bolt to the exhaust manifold. Tighten: Tighten the bolt to 25 N.m (18 lb ft).
5. Lower the vehicle.
6. Install the EGR valve outlet pipe. Refer to «Exhaust Gas Recirculation (EGR) Outlet Pipe Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
7. Install the EGR valve. Refer to «Exhaust Gas Recirculation (EGR) Valve Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
8. Install the exhaust manifold heat shield.
9. Install the exhaust manifold heat shield bolts (2). Tighten: Tighten the bolts to 10 N.m (89 lb in).
10. Install the HO2S. Refer to «Heated Oxygen Sensor Replacement - Position 1»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
11. Install the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.

1. Remove the air cleaner intake duct. Refer to «Air Cleaner Intake Duct Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
2. Remove the exhaust gas recirculation (EGR) outlet pipe bolt (2) from the intake manifold.
3. Remove the EGR outlet pipe nut (3) from the EGR valve inlet adapter pipe (1).
4. Remove the EGR valve outlet pipe (1).

1. Install the EGR valve outlet pipe (1).
2. Install the EGR outlet pipe bolt (2) to the intake manifold. Tighten: Tighten the bolt to 25 N.m (18 lb ft).
3. Install the EGR outlet pipe nut (3) to the EGR valve inlet adapter pipe. Tighten: Tighten the nut to 25 N.m (18 lb ft).
4. Install the air cleaner intake duct. Refer to «Air Cleaner Intake Duct Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .

Exhaust Gas Recirculation (EGR) System Cleaning

1. Remove the exhaust gas recirculation (EGR) valve (2). Refer to «Exhaust Gas Recirculation (EGR) Valve Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
2. Depress the pintle several times using a pencil eraser or other suitable soft instrument. The pintle should move in and out smoothly. Replace the valve if the valve exhibits tendencies to stick.
3. Try to rotate the EGR valve electrical connector housing. Repeat for the coil housing. Replace the valve if the valve exhibits any looseness.
4. Inspect the EGR valve pintle and seat for deposits. Use a cloth or other suitable soft device to remove the deposits. Remove all loose particles. Replace the valve if the deposits are such that the pintle to base interface cannot be cleaned adequately to allow the pintle to seal against the seat. Damage to the powdered metal EGR valve base occurs if cleaned with solvents, sharp tools, wire brush or wheel or sand blasting. Cleaning by these methods is not recommended.
5. Remove the EGR pipes. Refer to «Exhaust Gas Recirculation (EGR) Inlet Pipe Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) and «Exhaust Gas Recirculation (EGR) Outlet Pipe Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
6. Clean the passages with a wire brush. Remove all loose particles.
7. Install the EGR pipes. Refer to «Exhaust Gas Recirculation (EGR) Inlet Pipe Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) and «Exhaust Gas Recirculation (EGR) Outlet Pipe Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
8. Install the EGR valve. Refer to «Exhaust Gas Recirculation (EGR) Valve Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .

1. Remove the air cleaner intake duct. Refer to «Air Cleaner Intake Duct Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
2. Unclip the retaining fasteners (4) on the air cleaner cover.
3. Remove the air cleaner cover.
4. Remove the air cleaner element (1) from the air cleaner housing (2).

1. Install the air cleaner element (1) to the air cleaner housing (2).
2. Install the air cleaner cover and clip the cover retaining fasteners (4).
3. Install the air cleaner intake duct. Refer to «Air Cleaner Intake Duct Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .

1. Remove the left inner fender brace. Refer to «Brace Replacement - Front Fender Upper Diagonal»(/buick/lacrosse/i-2004-2009/remont/exterior-body-panels/#body-front-end) in Body Front End.
2. Remove the air cleaner intake duct. Refer to «Air Cleaner Intake Duct Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
3. Remove the air cleaner housing screws (2).
4. Remove the air cleaner housing cover (1) from the air cleaner housing.
5. Without disconnecting the powertrain control module (PCM) connectors, remove the PCM and the harness from the air cleaner housing.
6. Remove the air cleaner housing (1) by pulling the housing from the 2 rubber grommets (2) in the engine compartment.
7. Inspect the air cleaner housing assembly for signs of damage and replace if necessary.

1. Install the air cleaner housing by pushing the housing (1) into the 2 rubber grommets (2) in the engine compartment.
2. Install the PCM and the harness into the air cleaner housing (3).
3. Install the air cleaner housing cover assembly (1).
4. Install the air cleaner housing screws (2). Tighten: Tighten the screws to 3 N.m (27 lb in).
5. Install the air cleaner intake duct. Refer to «Air Cleaner Intake Duct Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) .
6. Install the left inner fender brace. Refer to «Brace Replacement - Front Fender Upper Diagonal»(/buick/lacrosse/i-2004-2009/remont/exterior-body-panels/#body-front-end) in Body Front End.

1. Remove the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.
2. Disconnect the MAF/IAT sensor electrical connector (2).
3. Disconnect the PCV tube.
4. Loosen the air cleaner intake duct clamps at the throttle body and the air cleaner housing cover.
5. Remove the air cleaner intake duct from the air cleaner cover.
6. Remove the air cleaner intake duct from the throttle body.
7. Remove the MAF/IAT sensor from the air cleaner intake duct.
8. If replacing the air cleaner intake duct, remove the clamps.

1. If removed, install the clamps to the air cleaner intake duct.
2. Install the MAF/IAT sensor to the air cleaner intake duct.
3. Install the air cleaner intake duct to the throttle body and the air cleaner cover. Tighten: Tighten the duct clamps to 3 N.m (27 lb in).
4. Connect the PCV tube.
5. Connect the MAF/IAT sensor electrical connector (2).
6. Install the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.

Powertrain Control Module (PCM) Description

The powertrain control module (PCM) interacts with many emission related components and systems and monitors emission related components and systems for deterioration. OBD II diagnostics monitor the system performance and a diagnostic trouble code (DTC) sets if the system performance degrades.

The malfunction indicator lamp (MIL) operation and the DTC storage are dictated by the DTC type. A DTC is ranked as a Type A or Type B if the DTC is emissions related. Type C is a non-emissions related DTC.

The PCM is in the engine compartment. The PCM is the control center of the engine controls system. The PCM controls the following components

1. The fuel injection system
2. The ignition system
3. The emission control systems
4. The on-board diagnostics
5. The A/C and fan systems

The PCM constantly monitors the information from various sensors and other inputs and controls the systems that affect the vehicle performance and the 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 MIL. When the PCM detects a malfunction, it stores a DTC. The condition is identified by the particular DTC that is set. This aids the technician in making repairs.

PCM Function

The powertrain control module (PCM) can supply 5 volts or 12 volts to the various sensors or switches. This is done through pull-up resistors to the regulated power supplies within the control module. In some cases, even an ordinary shop voltmeter will not give an accurate reading because the resistance is too low. Therefore, a DMM with at least 10 megaohms input impedance is required in order to ensure accurate voltage readings.

The PCM controls the output circuits by controlling the ground or the power feed circuit through the transistors or a device called an output driver module.

EEPROM

The electronically erasable programmable read only memory (EEPROM) is a permanent memory that is physically part of the control module. The EEPROM contains program and calibration information that the powertrain control module (PCM) needs in order to control the powertrain operation.

Special equipment, as well as the correct program and calibration for the vehicle, are required in order to reprogram the control module.

Data Link Connector (DLC)

The data link connector (DLC) is a 16-pin connector that provides the technician a means of accessing communication data for aid in the diagnosis. This connector allows the technician to use a scan tool in order to monitor the various parameters and display the DTC information. The DLC is located inside of the drivers compartment, underneath the dash.

Malfunction Indicator Lamp (MIL) Operation

The malfunction indicator lamp (MIL) is located in the instrument panel cluster. The MIL will display as either SERVICE ENGINE SOON or one of the following symbols when commanded ON

Scheme 85

Scheme 86

The MIL indicates that an emissions related fault has occurred and vehicle service is required. The following is a list of the modes of operation for the MIL

1. The MIL illuminates when the ignition is turned ON, with the engine OFF. This is a bulb test to ensure that the MIL is able to illuminate.
2. The MIL turns OFF after the engine is started if a diagnostic fault is not present.
3. The MIL remains illuminated after the engine is started if the control module detects a fault. A DTC is stored any time the control module illuminates the MIL due to an emissions related fault. The MIL turns OFF after 3 consecutive ignition cycles in which a Test Passed has been reported for the diagnostic test that originally caused the MIL to illuminate.
4. The MIL flashes if the control module detects a misfire condition which could damage the catalytic converter.
5. When the MIL is illuminated and the engine stalls, the MIL will remain illuminated as long as the ignition is ON.
6. When the MIL is not illuminated and the engine stalls, the MIL will not illuminate until the ignition is cycled OFF and then ON.

PCM Service Precautions

The powertrain control module (PCM), by design, can withstand the normal current draws that are associated with the vehicle operations. However, care must be used in order to avoid overloading any of these circuits. When testing for opens or shorts, do not ground or apply voltage to any of the PCM circuits unless the diagnostic procedure instructs you to do so. These circuits should only be tested with a DMM.

Emissions Diagnosis For State I/M Programs

This OBD II equipped vehicle is designed to diagnose any conditions that could lead to excessive levels of the following emissions

1. Hydrocarbons (HC)
2. Carbon monoxide (CO)
3. Oxides of nitrogen (NOx)
4. Evaporative emission (EVAP) system losses

Should this vehicles on-board diagnostic system, powertrain control module (PCM), detect a condition that could result in excessive emissions, the PCM turns ON the malfunction indicator lamp (MIL) and stores a DTC that is associated with the condition.

Aftermarket (Add-On) Electrical And Vacuum Equipment

Note. Do not attach add-on vacuum operated equipment to this vehicle. The use of add-on vacuum equipment may result in damage to vehicle components or systems.

Note. Connect any add-on electrically operated equipment to the vehicle's electrical system at the battery (power and ground) in order to prevent damage to the vehicle.

Aftermarket, add-on, electrical and vacuum equipment is defined as any equipment installed on a vehicle after leaving the factory that connects to the vehicles electrical or vacuum systems. No allowances have been made in the vehicle design for this type of equipment.

Add-on electrical equipment, even when installed to these strict guidelines, may still cause the powertrain system to malfunction. This may also include equipment not connected to the vehicle electrical system, such as portable telephones and radios. Therefore, the first step in diagnosing any powertrain condition is to eliminate all of the aftermarket electrical equipment from the vehicle. After this is done, if the problem still exists, the problem may be diagnosed in the normal manner.

Electrostatic Discharge (ESD) Damage

The electronic components that are used in the control systems are often designed to carry very low voltage. The electronic components are susceptible to damage caused by electrostatic discharge. Less than 100 volts of static electricity can cause damage to some electronic components. By comparison, it takes as much as 4,000 volts for a person to even feel the effect of a static discharge.

There are several ways for a person to become statically charged. The most common methods of charging are by friction and by induction. An example of charging by friction is a person sliding across a car seat.

Charging by induction occurs when a person with well insulated shoes stands near a highly charged object and momentarily touches ground. Charges of the same polarity are drained off leaving the person highly charged with the opposite polarity. Static charges can cause damage, therefore, it is important to use care when handling and testing electronic components.

Emissions Control Information Label

The underhood Vehicle Emissions Control Information Label contains important emission specifications and setting procedures. In the upper left corner is the exhaust emission information. This identifies the year, the manufacturing division of the engine, the displacement of the engine in liters, the class of the vehicle and type of fuel metering system. There is also an illustrated emission components and vacuum hose schematic.

This label is located in the engine compartment of every General Motors vehicle. If the label has been removed, it can be ordered from GM service parts operations (GMSPO).

Underhood Inspection

Perform a careful underhood inspection when performing any diagnostic procedure or diagnosing the cause of an emission test failure. This can often lead to repairing a condition without further steps. Use the following guidelines when performing an inspection

1. Inspect all of the vacuum hoses for correct routing, pinches, cuts or disconnects.
2. Inspect any hoses that are difficult to see.
3. Inspect all of the wires in the engine compartment for the following conditions: Burned or chafed spots Pinched wires Contact with sharp edges Contact with hot exhaust manifolds

Basic Knowledge Required

Note. Lack of basic knowledge of this powertrain when performing diagnostic procedures could result in incorrect diagnostic performance or damage to powertrain components. Do not attempt to diagnose a powertrain problem without this basic knowledge.

A basic understanding of hand tools is necessary in order to effectively use this information.

You must be familiar with some of the basics of engine operation and electrical diagnosis in order to use this service information.

1. Basic electrical circuits-You should have an understanding of basic electricity and know the meaning of voltage (volts), current (amps) and resistance (ohms). You should understand what happens in a circuit with an open or a shorted wire and you should be able to identify a shorted or open circuit by using a DMM. You should be able to read and understand a wiring diagram.
2. Use of digital multimeter-You should be familiar with the DMM, particularly the essential tool. You should be able to use the meter in order to measure the voltage (volts), the resistance (ohms), the current (amps), intermittents (min/max) and frequency (Hertz).
3. Use of circuit testing tools-You should not use a test lamp to diagnose the engine controls system unless you are specifically instructed to do so. You should know how to the use jumper wires in order to test the components and allow the DMM readings without damaging the terminals. You should know how to use the J 35616 connector test adapter kit and use the kit whenever the diagnostic procedures call for front probing any connector.

Purpose

The throttle actuator control (TAC) system delivers improved throttle response and greater reliability and eliminates the need for mechanical cable. The TAC system performs the following functions

1. Accelerator pedal position (APP) sensing
2. Throttle positioning to meet driver and engine demands
3. Throttle position sensing
4. Internal diagnostics
5. Cruise control functions
6. Manage TAC electrical power consumption

The TAC system includes the following components

1. The APP sensors
2. The throttle body assembly
3. The powertrain control module (PCM)

Accelerator Pedal Position (APP) Sensor

The accelerator pedal contains 2 individual accelerator pedal position (APP) sensors within the assembly. The APP sensors 1 and 2 are potentiometer type sensors each with 3 circuits

1. A 5-volt reference circuit
2. A low reference circuit
3. A signal circuit

The APP sensors are used to determine the pedal angle. The powertrain control module (PCM) provides each APP sensor with a 5-volt reference circuit and a low reference circuit. The APP sensors provide the PCM with signal voltage proportional to the pedal movement. Both APP sensor signal voltages are low at rest position and increase as the pedal is applied.

Throttle Body Assembly

The throttle assembly contains the following components

1. The throttle blade
2. The throttle actuator motor
3. The throttle position (TP) sensor 1 and 2
4. The throttle actuator control (TAC) module

The throttle body functions similar to a conventional throttle body with the following exceptions

1. There is no longer an idle air control (IAC) motor and associated air passages.
2. An electric motor opens and closes the throttle valve.
3. The TAC module is located within the throttle body assembly.
4. The throttle blade is spring loaded in both directions and the default position is slightly open.
5. There are 2 individual TP sensors within the throttle body assembly.

The TP sensors are used to determine the throttle plate angle. The TP sensors provide the powertrain control module (PCM) with a signal voltage proportional to throttle plate movement. Both TP sensor signal voltages are low at closed throttle and increase as the throttle opens.

Throttle Actuator Control Module

The throttle actuator control (TAC) module is the control center for the TAC system. The TAC system uses electronically erasable programmable read only memory (EEPROM) and is self-diagnosing. The TAC module provides diagnostic information to the powertrain control module (PCM) through a dedicated serial data line. The TAC achieves throttle positioning by providing a pulse width modulated (PWM) voltage to the TAC motor as directed by the PCM. The TAC module is not serviced and should be replaced with the throttle body assembly.

Powertrain Control Module

The powertrain control module (PCM) determines the drivers intent and then calculates the appropriate throttle response. This information is sent to the throttle actuator control (TAC) module through a dedicated serial data line.

Normal Mode

During the operation of the throttle actuator control (TAC) system, several modes or functions are considered normal. The following modes may be entered during normal operation

1. Minimum pedal value-At key-up, the powertrain control module (PCM) updates the learned minimum pedal value.
2. Minimum throttle position (TP) values-At key-up, the PCM updates the learned minimum throttle position value. In order to learn the minimum throttle position value, the throttle blade is moved to the closed position.
3. Ice break mode-If the throttle is not able to reach a predetermined minimum throttle position, the ice break mode is entered. During the ice break mode, the PCM commands the maximum pulse width several times to the throttle actuator motor in the closing direction.
4. Battery saver mode-After a predetermined time without engine RPM, the PCM commands the battery saver mode. During the battery saver mode, the TAC module removes the voltage from the motor control circuits, which removes the current draw used to maintain the idle position and allows the throttle to return to the spring loaded default position.

Reduced Engine Power Mode

When the PCM detects a condition with the TAC system, the PCM may enter a reduced engine power mode. Reduced engine power may cause one or more of the following conditions

1. Acceleration limiting-The PCM will continue to use the accelerator pedal for throttle control, however the vehicle acceleration is limited.
2. Limited throttle mode-The PCM will continue to use the accelerator pedal for throttle control however the maximum throttle opening is limited.
3. Throttle default mode-The PCM will turn off the throttle actuator motor and the throttle will return to the spring loaded default position.
4. Forced idle mode-The PCM will perform the following actions: Limit engine speed to idle by positioning the throttle or by controlling the fuel and spark if the throttle is turned off. Ignore the accelerator pedal input.
5. Engine shutdown mode-The PCM will disable fuel and de-energize the throttle actuator.

Fuel System Overview

The fuel tank stores the fuel supply. An electric fuel pump, located in the fuel tank with the fuel sender assembly, pumps fuel through an in-tank fuel filter to the fuel rail assembly. The pump provides fuel at a pressure that is more than is needed by the injectors. The fuel pressure regulator, part of the fuel rail assembly, keeps fuel available to the injectors at a regulated pressure.

Scheme 87

The fuel tank stores the fuel supply. The fuel tank is located in the rear 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.

Scheme 88

The fuel fill pipe (2) has a built-in restrictor and a deflector in order to prevent refueling with leaded fuel.

Scheme 89

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 quarter-turn type 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.

Scheme 90

The fuel sender assembly consists of the following major components

1. The fuel tank pressure (FTP) sensor (1)
2. The post not used (2)
3. The fuel feed (3)
4. The canister vent (4)
5. The fuel limiting vent valve (FLVV) (5)
6. The fuel level sensor (6)
7. The fuel pump and reservoir assembly (7)

Scheme 91

The fuel level sensor consists of a float, a wire float arm and a ceramic resistor card. The position of the float arm indicates the fuel level. The fuel level sensor contains a variable resistor which changes resistance in correspondence with the amount of fuel in the fuel tank. The powertrain control module (PCM) sends the fuel level information via the class 2 circuit to the instrument panel cluster (IPC). This information is used for the IPC fuel gage and the low fuel warning indicator, if applicable. The PCM also monitors the fuel level input for various diagnostics.

Scheme 92

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 rail 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 powertrain control module (PCM) 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.

Scheme 93

The fuel strainer attaches to the lower end of the fuel sender. The fuel strainer is made of woven plastic. The functions of the fuel strainer are to filter contaminants and to wick fuel. The fuel strainer is self-cleaning and normally requires no maintenance. Fuel stoppage at this point indicates that the fuel tank contains an abnormal amount of sediment or water.

Fuel Feed Pipe

The fuel feed pipe carries fuel from the fuel tank to the fuel rail assembly. The fuel pipes consist of 2 sections

1. The rear fuel pipe assembly is located from the top of the fuel tank to the chassis fuel pipe. The rear fuel pipes are constructed of nylon.
2. The chassis fuel pipe is located under the vehicle connects the rear fuel pipe to the fuel rail pipe. The chassis fuel pipe is constructed of steel.

Nylon Fuel Pipe

Nylon pipes are constructed to withstand maximum fuel system pressure, exposure to fuel additives and changes in temperature. There are 3 sizes of nylon pipes used

1. 9.53 mm (3/8 inch) ID for the fuel feed
2. 7.94 mm (5/16 inch) ID for the fuel return
3. 12.7 mm (1/2 inch) 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.

Fuel Pipe O-Rings

O-rings seal the threaded connections in the fuel system. Fuel system O-ring seals are made of special material. Service the O-ring seals with the correct service part.

Scheme 94

The fuel rail assembly attaches to the engine intake manifold. The fuel rail assembly performs the following functions

1. Positions the injectors in the intake manifold
2. Distributes fuel evenly to the injectors

Scheme 95

The fuel injector assembly is a solenoid operated device, controlled by the powertrain control module (PCM), that meters pressurized fuel to a single engine cylinder. The PCM 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. An injector stuck partly open can cause a loss of pressure after engine shutdown. Consequently, long cranking times would be noticed on some engines.

Scheme 96

The fuel pressure regulator attaches to the fuel module 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 manifold absolute pressure (MAP) sensor. The fuel pressure regulator is a serviceable part.

Fuel Metering Modes of Operation

The powertrain control module (PCM) monitors voltages from several sensors in order to determine how much fuel to give the engine. The PCM controls the amount of fuel delivered to the engine by changing the fuel injector pulse width. The fuel is delivered under one of several modes.

Starting Mode

When the ignition is first turned ON, the powertrain control module (PCM) energizes the fuel pump relay for 2 seconds. This allows the fuel pump to build pressure in the fuel system. The PCM calculates the air/fuel ratio based on inputs from the engine coolant temperature (ECT), mass air flow (MAF), 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 throttle position (TP) sensor is at wide open throttle (WOT), the powertrain control module (PCM) reduces the fuel injector pulse width in order to increase the air to fuel ratio. The PCM 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 PCM returns to the starting mode.

Run Mode

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

1. The HO2S has varying voltage output, showing that it 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 CL operation after reaching these values. In CL, the PCM 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 powertrain control module (PCM) increases the pulse width to the injectors to provide extra fuel during acceleration. This is also known as power enrichment. The PCM determines the amount of fuel required based upon the throttle position (TP), the engine coolant temperature (ECT), the manifold absolute pressure (MAP), the mass air flow (MAF) and the engine speed.

Deceleration Mode

When the driver releases the accelerator pedal, air flow into the engine is reduced. The powertrain control module (PCM) monitors the corresponding changes in throttle position (TP), manifold absolute pressure (MAP) and mass air flow (MAF). The PCM 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 powertrain control module (PCM) 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 powertrain control module (PCM) 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 the red line.
4. The vehicle speed is too high above the 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 3-way catalytic (TWC) converters

Fuel Trim

The powertrain control module (PCM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy and emission control. The PCM monitors the heated oxygen sensor (HO2S) signal voltage while in Closed Loop (CL) and regulates the fuel delivery by adjusting the pulse width of the injectors based on this signal. The ideal fuel trim (FT) values are around 0 percent for both short and long term FT. A positive FT value indicates the PCM is adding fuel in order to compensate for a lean condition by increasing the pulse width. A negative FT value indicates that the PCM 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 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 course 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 and long term FT values. The long term FT diagnostic is based on an average of several of the long term speed load learn cells. The PCM selects the cells based on the engine speed and engine load. If the PCM detects an excessively lean or rich condition, the PCM will set a FT diagnostic trouble code (DTC).

EVAP System Operation

The evaporative emission (EVAP) control system limits fuel vapors from escaping into the atmosphere. Fuel tank vapors are allowed to move from the fuel tank, due to pressure in the tank, through the vapor pipe, into the EVAP canister. Carbon in the canister absorbs and stores the fuel vapors. Excess pressure is vented through the vent line and EVAP canister vent solenoid valve to atmosphere. The EVAP canister stores the fuel vapors until the engine is able to use them. At an appropriate time, the control module will command the EVAP canister purge solenoid valve ON, open, allowing engine vacuum to be applied to the EVAP canister. With the EVAP canister vent solenoid valve OFF, open, fresh air will be drawn through the solenoid valve and vent line to the EVAP canister. Fresh air is drawn through the canister, pulling fuel vapors from the carbon. The air/fuel vapor mixture continues through the EVAP purge pipe and EVAP canister purge solenoid valve into the intake manifold to be consumed during normal combustion. The control module uses several tests to determine if the EVAP system is leaking.

Large Leak Test

This tests for large leaks and blockages in the evaporative emission (EVAP) system. The control module will command the EVAP canister vent solenoid valve ON, closed and command the EVAP canister purge solenoid 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 solenoid 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, a DTC P0455 will set.

Small Leak Test

If the large leak test passes, the control module will test for small leaks by continuing to monitor the fuel tank pressure (FTP) sensor for a change in voltage over a period of time. If the decay rate is more than a calibrated value, the control module will rerun the test. If the test fails again, a 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 canister purge solenoid valve ON, open; and commanding the EVAP canister vent solenoid 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 will set.

EVAP Purge Solenoid Valve Leak Test

If the evaporative emission (EVAP) canister 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 canister purge solenoid valve OFF, closed; and EVAP canister vent solenoid 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 will set.

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.

Electronic Ignition (EI) System Description

The electronic ignition (EI) system produces controls a high energy secondary spark. This spark is used to ignite the compressed air/fuel mixture at precisely the correct time. This provides optimal performance, fuel economy and control of exhaust emissions. This ignition system uses one coil for each pair of cylinders. Companion cylinders are a pair of cylinders that are at top dead center (TDC) at the same time. The cylinder that is at TDC of the compression stroke is called the event cylinder. The cylinder that is at TDC of the cylinder exhaust stroke is called the waste cylinder. When the coil is triggered both companion cylinder spark plugs fire at the same time, completing a series circuit. Because the lower pressure inside the waste cylinder offers very little resistance, the event cylinder uses most of the available voltage to produce a very high energy spark. This is known as waste spark ignition. The EI system consists of the following components

Crankshaft Position (CKP) Sensors

The crankshaft position (CKP) sensor has a 4-wire harness connector that plugs into the CKP sensor and connects to the ignition control module (ICM). The CKP sensor contains 2 hall-effect switches in 1 housing and shares a magnet between the switches. The magnet and each hall-effect switch are separated by an air gap. A hall-effect switch is a solid state switching device that produces a digital ON/OFF pulse when a rotating element passes the sensor pick-up and interrupts the magnetic field of the sensor. The rotating element is called an interrupter ring or blade. There are two interrupter rings built into the crankshaft balancer. The outer ring and the outer switch provide the ICM with 18X signals or 18 identical pulses per crankshaft revolution. The inner ring and the inner switch provide the ICM with 3 pulses per revolution, each 1 of different duration. This is called the sync pulse. Each sync pulse represents a pair of companion cylinders. The ICM supplies a 12-volt and a low reference circuit to the CKP sensor, which is also shared by the camshaft position (CMP) sensor. The 18X reference pulses are passed from the CKP sensor to the ICM on the CKP sensor 1 signal circuit. The sync pulses are passed from the CKP sensor to the ICM on the CKP sensor 2 signal circuit. The ICM uses the 18X and sync pulses to determine the crankshaft position by counting how many ON-OFF 18X pulses occur during a sync pulse. With this dual interrupter ring arrangement the ICM can identify the correct pair of cylinders to fire within as little as 120 degrees of crankshaft rotation.

Crankshaft Balance Interrupter Ring

Each interrupter ring has blades and windows that either block the magnetic field or allow it to close one of the hall-effect switches. The outer hall-effect switch sends a pulse called the 18X reference signal. The outer interrupter ring has 18 evenly spaced blades and windows. The 18X reference signal produces 18 ON-OFF pulses per crankshaft revolution. The inner hall-effect switch sends a pulse called the sync signal. The inner interrupter ring has 3 unevenly spaced blades and windows of different widths. The sync signal produces 3 different length ON-OFF pulses per crankshaft revolution. When the sync interrupter ring window is between the magnet and the inner switch, the magnetic field will cause the sync hall-effect switch to ground the supplied voltage from the ICM. The 18X interrupter ring and the hall-effect switch react similarly.

Camshaft Position (CMP) Sensor

The camshaft position (CMP) sensor signal is a digital ON/OFF pulse, output once per revolution of the camshaft. The CMP sensor does not directly affect the operation of the ignition system. The CMP sensor information is used by the powertrain control module (PCM) to determine the position of the valve train relative to the CKP. By monitoring the CMP and CKP signals the PCM can accurately time the operation of the fuel injectors. The CMP sensor shares 12-volt and low reference circuits with the CKP sensor. The CMP signal circuit is input to the ICM.

Knock Sensor (KS)

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.

The KS system uses one or two flat response two-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 the 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.

Ignition Control Module (ICM) and Ignition Coils

Three dual tower ignition coils are mounted to the ICM and are serviced individually. The ICM performs the following functions

1. The ICM supplies a power and low reference circuit to the CMP and CKP sensors.
2. The ICM determines the correct direction of the crankshaft rotation and cuts spark and fuel delivery to prevent damage from backfiring if reverse rotation is detected.
3. The ICM determines the correct coil triggering sequence, based on how many 18 X ON-OFF pulses occur during a sync pulse. This coil sequencing occurs at start-up and is remembered by the ICM. After the engine is running, the ICM will continue to trigger the coils without the CKP sync pulse.
4. The ICM inputs 18 X and 3 X reference signals to the PCM.
5. The 3 X reference signal is also known as the low resolution engine speed signal. This signal is generated by the ICM using an internal divide-by-six circuit. This circuit divides the 18 X signal pulses by 6. This divider circuit will not begin operation without a sync pulse present at start-up and without 18 X and 3 X reference signals no fuel injection will occur.

Powertrain Control Module (PCM)

The PCM maintains proper spark and fuel injection timing for all driving conditions. Ignition control (IC) spark timing is the method the PCM uses to control spark advance. To provide optimum driveability and emissions, the PCM monitors input signals from the following components to calculate ignition spark timing

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

The following describes the PCM to ICM circuits

1. Low resolution engine speed signal-3 X reference-PCM input-from the ICM. The 3X reference signal is produced by the ICM. The PCM uses this signal to calculate engine RPM and crankshaft position above 1,200 RPM. The PCM also uses the pulses on this circuit to initiate fuel injector operation. The PCM compares the number of 3X pulses to the number of 18X and cam pulses. If the number of 3X pulses are incorrect while the engine is cranking or running, the PCM will set a DTC. The engine will continue to start and run normally using the 18X reference signal.
2. Medium resolution engine speed signal-18 X reference-PCM input-from the ICM. The 18 X reference signal is used to accurately control spark timing at low RPM and allow ignition control (IC) operation during cranking. The ICM calculates the 18X reference signal by filtering the CKP sensor 18X pulses when the engine is running and the CKP sync pulses are being received. Below 1,200 RPM, the PCM is monitoring the 18X reference signal and using the 18X signal as the reference for ignition timing advance. The PCM compares the number of 18X pulses to the number of 3X and cam pulses. If the number of 18X pulses are incorrect while the engine is cranking or running, the PCM will set a DTC. The engine will continue to start and run normally using the 3X reference signal.
3. Camshaft position-PCM input-from the ICM. The PCM uses this signal to determine the position of the cylinder #1 piston during the pistons power stroke. This signal is used by the PCM to calculate true sequential fuel injection (SFI) mode of operation. The PCM compares the number of CAM pulses to the number of 18 X and 3 X reference pulses. If the number of 18 X and 3 X reference pulses occurring between CAM pulses is incorrect or if no CAM pulses are received while the engine is running, the PCM will set a DTC. If the CAM signal is lost while the engine is running the fuel injection system will shift to a calculated sequential fuel injection mode based on the last CAM pulse and the engine will continue to run. The engine can be re-started and will run in the calculated sequential mode as long as the condition is present with a 1 in 6 chance of being correct.
4. Low reference-PCM input-this is a ground circuit for the digital RPM counter inside the PCM, but the wire is connected to engine ground only through the ICM. This circuit assures there is no ground drop between the PCM and ICM.
5. IC timing signal-PCM output-to the ICM. The ICM controls spark timing while the engine is cranking, this is called bypass mode. Once the PCM receives 3 X reference signals from the ICM, the PCM applies 5 volts to the IC timing signal circuit allowing the ICM to switch spark advance to PCM control.
6. IC timing control-PCM output-to the ICM. The IC output circuitry of the PCM sends out timing signals to the ICM on this circuit. When in the Bypass Mode, the ICM grounds these signals. When in the IC Mode, the signals are sent to the ICM to control spark timing.

Modes of Operation

The PCM has 2 modes of operation. One is the Bypass mode during which the PCM does not apply 5 volts to the IC timing signal circuit, allowing the ICM to control the triggering of each coil for proper spark timing. The Bypass mode is used during each of the following conditions

1. Crank
2. Engine running below a desired RPM
3. Default mode due to a system failure

The other mode is the IC mode during which the PCM is receiving the 18X and the 3X reference pulses from the CKP sensor and is supplying 5 volts to the IC timing signal circuit. This allow the PCM to accurately control spark timing for all driving conditions.

Secondary Air Injection (AIR) System Description

The Secondary Air Injection (AIR) System aids in the reduction of hydrocarbon exhaust emissions during a cold start-up. This occurs when the start-up engine coolant temperature (ECT) is between 5-50°C (41-122°F) and the intake air temperature (IAT) is between 5-60°C (41-140°F). The AIR pump operates 5-60 seconds after start-up.

The powertrain control module (PCM) activates the AIR system by simultaneously supplying grounds to the AIR pump and the AIR valve relays. This action closes the relays' internal contacts. The AIR pump and the AIR control solenoid valve/pressure sensor assembly are in turn energized, the pump runs and the control/shut-off valve opens.

The AIR pump sends pressurized fresh air into the pipes/hoses through the open control/shut-off valve and into the bank 2 exhaust manifold. The extra air accelerates the catalyst operation, helping it to reach operating temperature faster. The AIR pump remains ON for a short period of time after the control/shut-off valve is commanded OFF. When the AIR pump is commanded OFF it will not run or be activated until the next vehicle start. When the AIR system is inactive, the closed AIR control/shut-off valve prevents air/exhaust flow in either direction.

The AIR system pressure sensor is used to monitor pressure at the AIR control solenoid valve/pressure sensor assembly inlet, during the commanded ON/OFF states.

The AIR system includes the following components

1. The AIR pump-The electric AIR pump supplies pressurized, filtered air to the AIR control/shut-off valve. The AIR pump is a turbine type pump that is permanently lubricated and requires no periodic maintenance.
2. The AIR solenoid-The AIR solenoids opens the AIR control/shut-off valve when the solenoid is energized by the AIR solenoid relay.
3. The AIR control solenoid valve/pressure sensor assembly-The AIR control solenoid valve/pressure sensor assembly has a solenoid mounted valve. When the valve is open by the solenoid, pressurized air from the AIR pump flows through the control solenoid valve/pressure sensor assembly and is directed into the bank 2 exhaust manifold through an outlet pipe.
4. The AIR pressure sensor-The AIR pressure sensor is a part of the AIR control solenoid valve/pressure sensor assembly. The sensor is a 3-wire sensor that measures the AIR system pressure at the AIR control solenoid valve/pressure sensor assembly inlet.
5. The AIR pump relay-The AIR pump relay supplies high current and battery voltage to the AIR pump. The PCM commands the relay ON by supplying a ground to the relay control circuit.
6. The AIR valve relay-The AIR valve relay supplies high current and battery voltage to the AIR solenoid. the PCM commands the relay ON by supplying a ground to the relay control circuit.
7. The pipes and hoses-The AIR system hose carries filtered air from the engine air cleaner to the AIR pump inlet. The pipe/hoses carry the air from the AIR pump to the AIR control solenoid valve/pressure sensor assembly and on to the exhaust manifold.
8. The inlet filter-The AIR system does not have a separate inlet air filter. Filtered air is drawn from the engine air cleaner assembly.

Results of Incorrect Operation

The powertrain control module (PCM) monitors the Secondary air injection (AIR) System for faults during cold start-up operation. When the system's pressure or relay circuits operations vary too far from the predicted values, a DTC will set. Diagnostics detect the following conditions

1. A partially blocked or leaking AIR system
2. A malfunctioning AIR pump
3. A malfunctioning AIR control solenoid valve/pressure sensor assembly
4. A malfunctioning AIR pressure sensor
5. A restricted exhaust system, forward of the catalytic converter
6. A malfunctioning AIR pump and AIR valve relay

The following DTCs set when an AIR system fault is detected

1. DTC P0411-An AIR system insufficient airflow fault condition has been detected.
2. DTC P0412-An AIR valve relay coil circuit fault condition has been detected.
3. DTC P0418-An AIR pump relay coil circuit fault condition has been detected.
4. DTC P2430-An AIR pressure sensor stuck in range fault condition has been detected.
5. DTC P2431-An AIR pressure sensor range/performance fault condition has been detected.
6. DTC P2432-An AIR pressure sensor signal voltage below the minimum range of the sensor fault condition has been detected.
7. DTC P2433-An AIR pressure sensor signal voltage is above the maximum range of the sensor fault condition has been detected.
8. DTC P2440-An AIR system airflow leak fault condition has been detected.
9. DTC P2444-An AIR pump stuck ON fault condition has been detected.

Exhaust Gas Recirculation (EGR) System

The exhaust gas recirculation (EGR) system is used to reduce the amount of nitrogen oxide (NOx) emission levels caused by combustion temperatures exceeding 816°C (1,500°F). It does this by introducing small amounts of exhaust gas back into the combustion chamber. The exhaust gas absorbs a portion of the thermal energy produced by the combustion process and thus decreases combustion temperature. The EGR system will only operate under specific temperature, barometric pressure (BARO) and engine load conditions in order to prevent driveability concerns and to increase engine performance.

Scheme 97

The linear exhaust gas recirculation (EGR) valve consists of the following

1. The EGR valve position sensor
2. The EGR valve position sensor cap
3. The bobbin and coil assembly
4. The valve pintle
5. The primary pole piece
6. The armature sleeve
7. The armature and base assembly
8. The exhaust gas inlet port
9. The exhaust gas outlet port

Linear EGR Control

The linear exhaust gas recirculation (EGR) valve is controlled by a high side driver within the powertrain control module (PCM). This high side driver uses a 12-volt pulse width modulated (PWM) signal. The ground path for the EGR valve is completed by turning in a separate driver within the PCM. The PCM calculates the amount of EGR needed based on the following inputs

1. The engine coolant temperature (ECT) sensor
2. The intake air temperature (IAT) sensor
3. The barometric pressure (BARO)
4. The manifold absolute pressure (MAP) sensor
5. The throttle position (TP) sensor
6. The mass air flow (MAF) sensor

EGR Diagnostics

The powertrain control module (PCM) tests the exhaust gas recirculation (EGR) flow during deceleration by momentarily commanding the EGR valve to open while monitoring the signal of the manifold absolute pressure (MAP) sensor. When the EGR valve is opened, the PCM will expect to see a predetermined increase in MAP. If the expected increase in MAP is not detected, the PCM records the amount of MAP difference that was detected and adjusts a calibrated fail counter towards a calibrated fail threshold level. When the fail counter exceeds the fail threshold level, the PCM will set a DTC.

Normally, the PCM will only allow one EGR Flow Test Count during an ignition cycle. To aid in verifying a repair, the PCM allows 18 EGR Flow Test Counts during the first ignition cycle following a code clear or a battery disconnect. Between 9-18 EGR Flow Test Counts should be sufficient for the PCM to determine adequate EGR flow and pass the EGR flow test. If the PCM detects an EGR flow error, a DTC will set.

The PCM monitors the position of the EGR valve pintle via the EGR position sensor. If the PCM detects a calibrated variance between the Desired EGR Position parameter and the EGR Position Sensor parameter, actual position, for a calibrated amount of time a DTC will set.

The PCM also monitors the EGR solenoid high control circuit and the EGR solenoid low control circuit for electrical faults. If an EGR control circuit fault is detected for a calibrated amount of time a DTC will set.

Special Tools

Special Tools Illustration Tool Number/Description GE 41415-50 Fuel Tank Cap Adapter J 26792 Spark Tester J 34730-1A Fuel Pressure Gage J 34730-405 Injector Test Lamp J 35616 GM-Approved Terminal Test Kit J 35800-A Fuel Injector Cleaner J 36169-A Fused Jumper Wire J 37088-A Fuel Line Disconnect Tool Set J 37287 Fuel Line Shut-Off Adapters J 38491 Spark Plug Boot Removal Tool J 39021 Fuel Injector Coil & Balance Tester J 39021-380 Injector Tester Adapter J 39194 Oxygen Sensor Wrench J 41413-200 Evaporative Emission System Tester (EEST) J 41413-SPT High Intensity White Light J 41413-VLV EVAP Service Port Vent Fitting J 41415-40 Fuel Tank Cap Adaptor J 42873-1 3/8 Fuel Line Shut-Off Valve J 42873-2 5/16 Return Pipe Shut-Off Valve J 42964-1 3/8 Fuel Pipe Shut-Off Valve J 42964-2 5/16 Fuel Pipe Shut-Off Valve J 43244 Relay Puller Pliers J 44175 Fuel Composition Tester J 45722 Fuel Sender Lock Ring Wrench

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See also:
• DTC P0016
• DTC P0220
• DTC P0451
• DTC P2125
• Battery Negative Cable Disconnect/Connect Procedure (L26)
• Brace Replacement - Front Fender Upper Diagonal
• Fastener Notice
• Control Module References
• Diagnostic Trouble Code (DTC) List - Vehicle
• Draining and Filling Cooling System (L26 Static Fill)
• Fuel Injector Sight Shield Replacement
• Heated Oxygen Sensor (HO2S) Resistance Learn Reset Notice
• Lifting and Jacking the Vehicle
• Closeout/Insulator Panel Replacement - Left
• Air Cleaner Intake Duct Replacement
• COVER AND PLUG OPENINGS NOTICE
• FUEL SYSTEM GROUND NOTICE
• FUEL RAIL NOTICE
• Engine Mechanical Specifications
• Air Cleaner Intake Duct Replacement
• Special Tools
• Fuel Pressure Relief Procedure
• Fuel Tank Draining Procedure
• Fastener Tightening Specifications
• Ignition System Specifications
• CKP System Variation Learn Procedure