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Home >> Saturn >> 2000 >> LS Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0502: VSS Circuit - Low Input (A/T) >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
  2. Start engine. Using scan tool, monitor TOSS. Drive vehicle at greater than 3 MPH. If a signal is displayed on scan tool, problem is intermittent. See DIAGNOSTIC AIDS . If no signal is displayed on scan tool, go to next step.
  3. Turn ignition off. Disconnect PCM harness connectors J1 and J2. Using a DVOM, check resistance between PCM harness connector J1 terminal No. 64 (Yellow wire) and harness connector J2 terminal No. 61 (Purple wire). If resistance reading is 1500-1870 ohms, go to next step. If resistance reading is less than 1500 ohms, go to step  6. If resistance reading is greater than 1870 ohms, go to step  7.
  4. Disconnect transaxle output shaft speed sensor harness connector. Check for continuity between ground and transaxle output shaft speed sensor harness connector terminal "B" (Yellow wire). If continuity exists, repair short to ground in Yellow wire circuit. If continuity does not exist, go to next step.
  5. Reconnect transaxle output speed sensor. Set DVOM to AC scale. Connect DVOM to PCM harness connector J1 terminal No. 64 (Yellow wire) and harness connector J2 terminal No. 61 (Purple wire). Rotate drive wheel by hand at greater than 3 MPH. If voltage reading is greater than 500 mV, check for terminal tightness at connectors. Repair as necessary. If terminals are okay, replace PCM. If voltage reading is not greater than 500 mV, check sensor for correct torque. If torque is okay, replace transaxle output speed sensor.
  6. Disconnect transaxle output shaft speed sensor harness connector. Check for continuity between transaxle output shaft speed sensor harness connector terminals "A" (Purple wire) and B" (Yellow wire). If continuity exists, repair short between Yellow and Black wire circuits. If continuity does not exist, replace sensor.
  7. Disconnect transaxle output shaft speed sensor harness connector. Check for open in output shaft speed sensor harness connector terminal "A" (Purple wire ) and "B" (Yellow wire) circuits. If continuity exists in both circuits, check for terminal tightness in connectors. Repair as necessary. If terminals are okay, replace sensor. If continuity does not exist in both circuits, repair open in Purple or Yellow wire circuits.
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