Monday, March 7, 2011

how to test Chevy accelerator pedal sensor and other parts?

The accelerator pedal or lever position sensor sends a signal to the ECM when the operator pushes on the accelerator pedal or lever. The accelerator position circuit consists of the accelerator pedal or lever position sensor, the ECM, accelerator pedal/lever position +5 volt, accelerator pedal/lever position signal, and accelerator pedal/lever position return wires.

Then monitor the accelerator position sensor for proper operation. If not, follow the troubleshooting procedures in this section. Disconnect the 3-pin connector from the accelerator position sensor.
Connect the test connector.

Connect the multimeter positive (+) test lead to the accelerator pedal/lever position +5 volt supply test connector wire. Connect the negative (-) multimeter test probe to the accelerator pedal/lever position return test connector wire. Measure the resistance. The multimeter
must show between 2000 and 3000 ohms when the accelerator pedal is released (idle position) or depressed (full -fuel position). If the resistance is not within the specification, the accelerator position sensor has failed. Replace the accelerator position sensor.

Remove the multimeter probe from the accelerator pedal/lever position +5 volt supply test connector wire and connect it to the accelerator pedal/lever position signal test connector wire.
When the accelerator pedal is in the released (idle) position, measure the resistance. The multimeter must show between 1500 and 3000 ohms.

Depress the accelerator pedal assembly (full-fuel position) and measure the resistance. The multimeter must show between 250 and 1500 ohms. This resistance value must be at least 1000 ohms lower than the resistance value of 1500 to 3000 ohms measured in the above check. If the resistance values in the two previous steps are not within the specification, the accelerator position sensor has failed. Replace the accelerator position sensor according to the vehicle manufacturer's procedures.


NOW TO CONFIRM ITS FAULTY WIRING OR FAULTY APS.
Check short circuits for ground wiring and connections:----
Connect the multimeter positive (+) probe to the accelerator pedal/lever position return test connector wire. Touch the negative (-) multimeter probe to the chassis ground and measure the resistance. The multimeter must show an open circuit (100k ohms or more).

Remove the multimeter positive (+) probe from accelerator pedal/lever position return test connector wire and connect it to the accelerator pedal/lever position signal test connector wire. Measure the resistance. The multimeter must show an open circuit (100k ohms or more).


Remove the multimeter positive (+) probe from the accelerator pedal/lever position signal test connector wire and connect it to the accelerator pedal/lever position +5 volt supply test connector wire. Measure the resistance. The multimeter must show an open circuit (100k ohms or more). If the resistance values are not within the specifications in the previous check, the
accelerator position sensor has failed. Replace the accelerator position sensor according to the vehicle manufacturer's procedures.


To replace the accelerator pedal sensor follow this procedure as follows:------

Accelerator Pedal Position Sensor Replacement
REMOVAL PROCEDURE:---


Notice: Handle the electronic throttle control components carefully. Use cleanliness in order to prevent damage. Do not drop the electronic throttle control components. Do not roughly handle the electronic throttle control components. Do not immerse the electronic throttle control components in cleaning solvents of any type.


  1. Right click on the image and select option "open image in new web" if the image is not seen full or its very small to see.-----------


  2. Remove the connector position assurance (CPA) retainer.
  3. Disconnect the accelerator pedal position (APP) sensor electrical connector.
  4. Reposition the carpet to access the lower nut.

    Right click on the image and select option "open image in new web" if the image is not seen full or its very small to see.-----------


  5. Remove the accelerator pedal nuts.
  6. Remove the accelerator pedal assembly.
INSTALLATION PROCEDURE:----
  1. Install the accelerator pedal assembly. Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

  2. Install the accelerator pedal nuts. Tighten
    Tighten the nuts to 20 N·m (15 lb ft).
  3. Connect the APP sensor electrical connector.
  4. Reposition the carpet.
  5. Connect a scan tool in order to test for proper throttle-opening and throttle-closing range.
  6. Operate the accelerator pedal and monitor the throttle angles. The accelerator pedal should operate freely, without binding, between a closed throttle, and a wide open throttle (WOT).
  7. Verify that the vehicle meets the following conditions:
    The vehicle is not in a reduced engine power mode.
    The ignition is ON.
    The engine is OFF.
  8. Inspect the carpet fit under the accelerator pedal


  9. ----------------------
  10. For checking tachometer:----
  11. In vehicles equipped with this connector, a tachometer may be connected between terminals 6 and G.
    A tachometer connection is incorporated in the wiring connector on the side .

  12. Never connect a wire directly between the Tach terminal of the connector and ground as this will damage the electronic circuitry of the module. When using a timing light to adjust ignition timing, the connection should be made at the No. 1 spark plug. Forcing foreign objects through the boot at the No. 1 spark plug terminal will damage the boot and cause engine misfire.

  13. To find a tachometer wire with a multi-meter:
    1. Set meter to AC voltage.
    2. Attach the (-) probe of the meter to chassis ground.
    3. Start and run the vehicle
    4. Probe the wire suspected of being the tachometer wire with the other prob
    5. If this is the correct wire, the meter will read between 1V and 6V. This wire will increase in voltage as the RPMs are increased.----------------------------------
  14. Connect the tachometer tester probe to terminal IG of the Data Link Connector . Connect terminals TE1 and E1 of the DLC1 with a jumper connector.Inspect the tachometer's timing. It should be between 8 and 12 degrees Before Top Dead Center. Set the timing as necessary.Tighten the hold-down bolt and make sure the ignition timing advances.



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