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Home >> Saturn >> 2000 >> LS1 Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0502: VSS Circuit - Low Input (M/T Without Abs) >> 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. Drive vehicle. Using scan tool, monitor vehicle speed. If vehicle speed is displayed, problem is intermittent. See DIAGNOSTIC AIDS . If vehicle speed is not displayed, go to next step.
  3. Turn ignition off. Disconnect vehicle speed signal conditioner module harness connector located above hood release handle. Turn ignition on, with engine off. Using a DVOM, check voltage between ground and conditioner module harness connector terminal No. 5 (Brown wire). If battery voltage is present, go to next step. If battery voltage is not present, check for open or short in circuit. See WIRING DIAGRAMS article. Repair as necessary.
  4. Measure voltage between vehicle speed signal conditioner module harness connector terminals No. 1 (Black wire) and No. 5 (Brown wire). If battery voltage is present, go to next step. If battery voltage is not present, repair open in Black wire circuit.
  5. Connect a jumper wire to vehicle speed signal conditioner module harness connector terminal No. 4 (White wire) and quickly touch other end of jumper wire to ground. Observe vehicle speed reading scan tool. If vehicle speed changes, go to step  7. If vehicle speed does not change, go to next step.
  6. Using DVOM, check voltage between ground and harness connector terminal No. 4 (White wire). If voltage reading is 0-4 volts, check for terminal tightness or open or short in White wire circuit. Repair as necessary. If circuit or terminals are okay, replace PCM. If voltage reading is 4-6 volts, replace PCM. If voltage reading is greater than 6 volts, check for short to voltage in White wire circuit. Repair as necessary. If circuit is okay, replace PCM.
  7. Turn ignition off. Using DVOM, check resistance between vehicle speed signal conditioner module harness connector terminals No. 2 (Dark Green wire) and No. 3 (Tan wire). If resistance is 1000-2000 ohms, go to next step. If resistance is not 1000-2000 ohms, check for open in circuits or for terminal tightness. Repair as necessary. If circuits or terminals are okay, replace right front wheel speed sensor.
  8. Raise and support right front wheel. Using DVOM, check AC voltage between vehicle speed signal conditioner module harness connector terminals No. 2 (Dark Green wire) and No. 3 (Tan wire), while manually spinning wheels. If AC voltage does not increase when wheels are spun, go to next step. If AC voltage increases when wheels are spun, check for terminal tightness at connectors. Repair as necessary. If terminals are okay, replace vehicle speed signal conditioner module.
  9. Check gap between sensor and reluctor wheel. Check for missing or damaged reluctor wheel or wheel speed sensor. Repair or replace as necessary.
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