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

Testing & Diagnostics 1 illustration ~855 words

Disassembly Procedure

  1. Remove the fuel feed pipe from the fuel module and retaining clip.
  2. Remove the EVAP solenoid pipe (3) from the vent solenoid valve and the EVAP canister. Refer to «Quick Connect Fitting(s) Service (Plastic Collar)»(ref-200373-S38404922092005102000000) .
  3. Remove the EVAP pipe assembly (2) from the fuel tank vent valves, the fuel module, and the EVAP canister. Refer to «Quick Connect Fitting(s) Service (Plastic Collar)»(ref-200373-S38404922092005102000000) .
  4. Remove the EVAP canister purge pipe (1) from the EVAP canister and retaining clip. Refer to «Quick Connect Fitting(s) Service (Plastic Collar)»(ref-200373-S38404922092005102000000) .
  5. Remove the EVAP vent valve (9). Refer to «Evaporative Emission (EVAP) Canister Vent Solenoid Valve Replacement»(ref-200373-S30695037232005102000000) .
  6. Remove the fuel sender assembly (3) from the fuel tank. Refer to «Fuel Sender Assembly Replacement»(ref-200372-S24643162872005102000000) .
  7. Remove the EVAP canister (2). Refer to «Evaporative Emission (EVAP) Canister Replacement (TrailBlazer, Envoy, Rainier)»(ref-200372-S40072272842005102000000) «Evaporative Emission (EVAP) Canister Replacement (TrailBlazer EXT, Envoy XL, Envoy XUV)»(ref-200373-S19833679882005102000000) .

Assembly Procedure

  1. Install the EVAP canister (2). Refer to «Evaporative Emission (EVAP) Canister Replacement (TrailBlazer, Envoy, Rainier)»(ref-200372-S40072272842005102000000) «Evaporative Emission (EVAP) Canister Replacement (TrailBlazer EXT, Envoy XL, Envoy XUV)»(ref-200373-S19833679882005102000000) .
  2. Install the fuel sender assembly (3) to the fuel tank. Refer to «Fuel Sender Assembly Replacement»(ref-200372-S24643162872005102000000) .
  3. Install the EVAP vent valve (9). Refer to «Evaporative Emission (EVAP) Canister Vent Solenoid Valve Replacement»(ref-200373-S30695037232005102000000) .
  4. Install the EVAP canister purge pipe (1) to the EVAP canister and retaining clip. Refer to «Quick Connect Fitting(s) Service (Plastic Collar)»(ref-200373-S38404922092005102000000) .
  5. Install the EVAP pipe assembly (2) to the fuel tank vent valves, the fuel module, and the EVAP canister. Refer to «Quick Connect Fitting(s) Service (Plastic Collar)»(ref-200373-S38404922092005102000000) .
  6. Install the EVAP solenoid pipe (3) to the vent solenoid valve and the EVAP canister. Refer to «Quick Connect Fitting(s) Service (Plastic Collar)»(ref-200373-S38404922092005102000000) .
  7. Install the fuel feed pipe to the fuel module and retaining clip.
  1. Cut and remove the tie (2) securing the fuel feed pipe and EVAP canister purge pipe together.
  2. Remove the fuel feed pipe (1) from the fuel sender module (4) and retaining clip (3). Refer to «Quick Connect Fitting(s) Service (Plastic Collar)»(ref-200372-S03438683812005102000000) .
  3. Cut and remove the tie (1) securing the EVAP pipes together.
  4. Disconnect the EVAP pipe assembly (3) from the tank vent valves and fuel sender. Refer to «Quick Connect Fitting(s) Service (Plastic Collar)»(ref-200372-S03438683812005102000000) .
  5. Remove the EVAP pipe assembly (3) from the tank.
  6. Remove the EVAP canister purge pipe (2) from the fuel tank.
  7. Remove the EVAP vent valve (8). Refer to «Evaporative Emission (EVAP) Canister Vent Solenoid Valve Replacement»(ref-200372-S24136167682005102000000) .
  8. Remove the fuel sender assembly (4) from the fuel tank. Refer to «Fuel Sender Assembly Replacement»(ref-200372-S24643162872005102000000) .
  1. Install the fuel sender assembly (4) to the fuel tank. Refer to «Fuel Sender Assembly Replacement»(ref-200372-S24643162872005102000000) .
  2. Install the EVAP vent valve (8). Refer to «Evaporative Emission (EVAP) Canister Vent Solenoid Valve Replacement»(ref-200372-S24136167682005102000000) .
  3. Install the EVAP canister purge pipe (2) to the fuel tank.
  4. Install the EVAP pipe assembly (3) to the fuel tank.
  5. Connect the EVAP pipe assembly (3) to the tank vent valves and fuel sender. Refer to «Quick Connect Fitting(s) Service (Plastic Collar)»(ref-200372-S03438683812005102000000) .
  6. Install a new tie (1) to secure the EVAP pipes together.
  7. Install the fuel feed pipe (1) to the fuel sender module (4) and retaining clip (3). Refer to «Quick Connect Fitting(s) Service (Plastic Collar)»(ref-200372-S03438683812005102000000) .
  8. Install a new tie (2) securing the fuel feed pipe and EVAP canister purge pipe together.
  1. Remove the fuel injector wire harness (2) from the fuel rail (1).
  2. Remove the fuel injectors (4) from the fuel rail (4). Refer to «Fuel Injector Replacement»(ref-200372-S17152680902005102000000) .
  1. Install the fuel injector harness (2) to the fuel rail (1).
  2. Install the fuel injectors (3) to the fuel rail. Refer to «Fuel Injector Replacement»(ref-200372-S17152680902005102000000) .

Throttle Body Assembly

The throttle body for the TAC system is similar to a conventional throttle body with several exceptions. One exception being the use of a motor to control the throttle position instead of a mechanical cable. Another exception is the throttle position (TP) sensor. The TP sensor is mounted in the throttle body assembly. The TP sensor is 2 individual TP sensors within the throttle body assembly. Two separate signal, low reference, and 5-volt reference circuits are used to connect the TP sensors and the PCM. TP sensor 2 signal voltage increases as the throttle opens. TP sensor 1 signal voltage decreases as the throttle opens.

Fuel Sender Assembly

The fuel sender assembly consists of the following major components

  1. The fuel pump
  2. The fuel level sensor
  3. The fuel filter
  4. The fuel pressure regulator

Scheme 24

Scheme 24: Fuel Level Sensor
Scheme 24: Fuel Level Sensor

The fuel level sensor (1) 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 position of the float arm. The control module 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 control module also monitors the fuel level input for various diagnostics.

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