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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 69 (Automatic Transmission Diagnosis - 4L80-E (Diesel)) >> Diagnostic Tests >> DTC P0717: ISS Sensor Circuit - Low Input >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2002 GMC Cab & Chassis Sierra and 2002 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the diagnostic system check? If so, go to next step. If not, see DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM.
  2. Install a scan tool. Turn ignition on, engine off. Before clearing the DTC, use the scan tool to record the freeze frame and failure records for reference. The CLEAR INFO function will erase the data. Record the DTC freeze frame and failure records. Clear the DTC. Raise and support the rear axle assembly. Start the engine. Place the gearshift lever in the "D3" position. With the drive wheels rotating, slowly accelerate to 2000 engine RPM and hold. Is the scan tool ISS more than 800 RPM? If so, see DIAGNOSTIC AIDS  . If not, go to next step.
  3. Turn ignition off. Disconnect wire harness connector from the ISS. Remove the ISS from the transmission. Using a DVOM and Connector Test Adapter Kit (J-35616-A), measure the resistance of the ISS. Does the sensor resistance measure 1042-2088 ohms? If so, go to next step. If not, go to step  11 .
  4. Test the ISS high signal circuit (1230) for an open or short to ground between the PCM connector C1 terminal D11 and ISS connector terminal No. 1. Did you find and correct the condition? If so, go to step  13 . If not, go to next step.
  5. Test the ISS low signal circuit (1231) for an open between the PCM connector C1 terminal D1 and ISS connector terminal No. 2. Did you find and correct the condition? If so, go to step  13 . If not, go to next step.
  6. Turn ignition on, engine off. Measure the voltage from ISS connector terminal No. 1 to a good ground. Does the voltage measure 4.0-5.1 volts? If so, go to next step. If not, go to step  8 .
  7. Turn ignition on, engine off. Measure the voltage at ISS connector terminal No. 2. Does the voltage measure less than 0.2 volt? If so, go to step  10 . If not, go to step  9 .
  8. Is the voltage reading in step  6 greater than 5.1 volts? If so, go to next step. If not, go to step  12 .
  9. Test the ISS high signal circuit (1230) and the ISS low signal circuit (1231) for a short to voltage or shorted together between the PCM connector C1 and the ISS harness connector. Did you find and correct the condition? If so, go to step  13 .
  10. Install the ISS in the transmission. Connect the ISS harness connector to the sensor. Disconnect the PCM connector C1. Additional DTCs may set. Using DVOM set to AC scale, probe across PCM connector C1 terminals D1 and D11. Remove the fuel pump relay. With the vehicle in Park, crank the engine. Does the voltage measure above 0.5 volt? If so, go to step  12 .
  11. Replace the ISS. See SPEED SENSORS  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step  13 .
  12. Replace the PCM. See POWERTRAIN CONTROL MODULE  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to next step.
  13. Perform the following procedure to verify the repair:
    • Select DTC.
    • Select CLEAR INFO.
    • Operate the vehicle at a speed greater than 12 MPH.
    • The PCM must see an input speed greater than 500 RPM for one second.
    • Select SPECIFIC DTC.
    • Enter DTC P0717.

    Has the test run and passed? If so, system is okay. If not, go to step  1 .

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