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HOMESERVICE MANUALSOLDSMOBILE1998ACHIEVA 3.1 M, 4T40E/MN4REPAIR AND DIAGNOSIS (SINGLE PAGE)TRANSMISSIONAUTOMATIC TRANSAUTOMATIC TRANSAXLE DIAGNOSIS - 4T60-EDIAGNOSTIC TESTSDTC P0502: VEHICLE SPEED SENSOR CIRCUIT (LOW INPUT)DIAGNOSTIC PROCEDURE
1998 Oldsmobile Achieva 3.1 M, 4T40E/MN4

Diagnostic Procedure

1998 Oldsmobile Achieva 3.1 M, 4T40E/MN4SECTION Diagnostic Procedure
  1. Connect scan tool to DLC. Turn ignition switch to ON position. DO NOT start engine. Using scan tool, record freeze frame and failure records for reference. Data will be lost when DTCs are cleared later in this test. Raise and support vehicle.
    CAUTION: To prevent damage to drive axles, support lower control arms in normal horizontal position.
  2. Start engine and let idle. Shift gear selector to "D" position. Select "Output Speed" on scan tool. With drive wheels rotating, if transaxle output speed does not increase when wheel speed increases, go to next step. If transaxle output speed increases when wheel speed increases, cause is intermittent. See DIAGNOSTIC AIDS.
  3. Use scan tool to check for most current PCM calibration I.D. number. Refer to TECHNICAL SERVICE BULLETINS section if necessary. If I.D. number matches, go to next step. If I.D number does not match, update PCM with latest calibration, then go to step 9).
  4. Turn ignition off. On models with 2.4L engine, disconnect both PCM 80-pin connectors. On all other models, disconnect Blue PCM 80-pin connector C1. See Figure and Figure. PCM is located at right side of instrument panel, behind glove box.
  5. On models with 2.4L engine, connect voltmeter between VSS terminals at PCM Blue and Black connector (C1 and C2). See Figure. See WIRING DIAGRAMS . On 3.1L models, connect voltmeter between VSS terminals at PCM Blue connector (C1). See Figure and Figure. See WIRING DIAGRAMS . Select AC volts on voltmeter. On all models, rotate drive wheels and observe voltmeter display. If voltage is more than .5 volt, replace PCM, then go to step 9). If voltage is less than .5 volt, go to next step.
  6. Connect ohmmeter to appropriate VSS terminals at PCM connector(s). See WIRING DIAGRAMS . If resistance is more than 1864 ohms, check for open in VSS wires between PCM connector and VSS. Repair wires as necessary, then go to step 9). If wires are okay, go to next step. If resistance is less than 981 ohms, go to step 8).
  7. Remove VSS from transaxle. Connect ohmmeter between VSS terminals. If resistance is 981-1864 ohms, inspect sensor ring on final drive carrier assembly for damage and misalignment. Repair as necessary, then go to step 9). If resistance is not 981-1864 ohms, replace VSS, then go to step 9).
  8. Check for VSS wires shorted together. Repair wires as necessary, then go to next step. If resistance is more than 941 ohms, check for short to ground in circuits between VSS and PCM. Repair circuits as necessary, then go to next step.
  9. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Select "Specific DTC" and enter DTC "P0502". Test drive vehicle at output speed more than 250 RPM for 3 seconds. If DTC P0502 is not present, repair is complete. If DTC P0502 is still present, repeat test.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.