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Home >> Chevrolet >> 2001 >> Venture Base, Van Passenger >> Repair and Diagnosis >> External Pages >> Different car >> Section 26 (Engine Controls Self-Diagnostics - 5.0L & 5.7L) >> Diagnostic Tests >> DTC P0503: Vehicle Speed Sensor Erratic >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2001 GMC Savana, 2001 Chevrolet RV Cutaway, 2001 Chevrolet Cutaway, and 2001 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
    2. NOTE: Before clearing DTC, use scan tool to record FREEZE FRAME/FAILURE RECORDS. Using CLEAR INFO function erases FREEZE FRAME/FAILURE RECORDS from PCM.
  2. Install scan tool. Turn ignition on, engine off. Record DTC FREEZE FRAME/FAILURE RECORDS. Clear DTC. Raise and support rear axle assembly. Start engine. Place transmission in D3 range. With drive wheels rotating, slowly accelerate to 2000 engine RPM and hold. (Road test vehicle if necessary.) If scan tool TRANSMISSION OSS drop or fluctuates more than 1300 RPM, go to next step. If scan tool TRANSMISSION OSS does not drop or fluctuates more than 1300 RPM, seeINTERMITTENT TROUBLE CODE DETERMINATION  under ON-BOARD DIAGNOSTICS under SELF-DIAGNOSTIC SYSTEM.
  3. Turn ignition off. Disconnect PCM Red connector C2. Using DVOM and Connector Test Adapter Kit (J 35616-A), measure resistance between PCM Red connector C2 terminals No. 20 (Light Green/White wire) and No. 21 (Purple/White wire). See Figure. If resistance is 1377-3355 ohms, go to next step. If resistance is not 1377-3355 ohms, go to step  7.
  4. Place transmission in Neutral. Select AC volts. Prevent one rear wheel from turning. Rotate the other rear wheel by hand, ensuring driveshaft is turning. If voltage is more than 0.5 volt, go to next step. If voltage is not more than 0.5 volt, go to step  12.
  5. Measure resistance between PCM Red connector C2 terminal No. 21 (Purple/White wire) and ground. If resistance is more than 50 k/ohms, go to next step. If resistance is not more than 50 k/ohms, go to step  9.
  6. Reconnect PCM Red connector C2. Disconnect engine wiring harness from VSS. VSS is located on transmission tail housing. Turn ignition on, engine off. Check Purple/White wire between PCM and VSS for short to power. If problem was found, repair as necessary. After repairs, go to step  15. If problem was not found, go to step  14.
  7. Disconnect engine wiring harness from VSS. Measure resistance between VSS sensor connector terminals (sensor side). If resistance is 1377-3355 ohms, go to next step. If resistance is not 1377-3355 ohms, go to step  13.
  8. If resistance measured in step  3 was greater than 3355 ohms, go to step  10. If resistance measured in step  3 was not greater than 3355 ohms , go to step  11.
  9. Repair short to ground in Light Green/Black wire or Purple/White wire between PCM and VSS. After repairs, go to step  15.
  10. Repair open in Light Green/Black wire or Purple/White wire between PCM and VSS, or repair open in Light Green/Black wire between PCM and VSS. After repairs, go to step  15.
  11. Repair short between Light Green/Black wire and Purple/White wire between PCM and VSS. After repairs, go to step  15.
  12. Remove VSS assembly. Inspect output shaft speed sensor rotor for damage or misalignment. Inspect case extension bushing for wear. If problem was found, repair as necessary. After repairs, go to step  15. If problem was not found, go to next step.
  13. Replace VSS assembly. After repairs, go to step  15.
  14. Replace PCM. Program PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  15. Using scan tool, clear DTC. Operate vehicle, ensuring transmission output speed drop is less than 500 RPM for 2 seconds and output speed is more than 500 RPM for 2 seconds. Using scan tool, check DTC. If DTC has run and passed, system is okay. If DTC has not run and passed, go to step  1.
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