LEMON Manuals: Even more car manuals for everyone
Home >> Chevrolet >> 1998 >> Monte Carlo LS >> Repair and Diagnosis >> Accessories & Equipment >> Gauges & Instrument Panels >> Symptom Tests >> SEO VF Digital Speedometer &/Or Odometer Inoperative Or Inaccurate

SEO VF Digital Speedometer &/Or Odometer Inoperative Or Inaccurate

  1. If vehicle has been checked for Diagnostic Trouble Codes (DTCs), go to next step. If vehicle has not been checked for DTCs, see appropriate TESTS W/CODES article in ENGINE PERFORMANCE section:
  2. Connect a scan tool to Data Link Connector (DLC). Drive vehicle and compare vehicle speed displayed on scan tool to instrument cluster speed display. If both speeds are similar, go to next step. If both speeds are not similar, go to step 6).
  3. If both speedometer and odometer are inaccurate, go to next step. If only speedometer or odometer is inaccurate, go to step 7).
  4. Check vehicle for correct tire size, PCM calibration and vehicle speed sensor application. If these component applications are okay, diagnose and repair DTC 24 (vehicle speed sensor). See appropriate TESTS W/CODES article in ENGINE PERFORMANCE section:

    If these component applications are not correct, go to next step.

  5. Replace tires or vehicle speed sensor, or recalibrate PCM as necessary. See TESTS W/CODES article in ENGINE PERFORMANCE section. Recheck system operation.
  6. If one or more speed-related feature besides instrument cluster (i.e., cruise control, ABS) is also malfunctioning, go to step 10). If other speed-related features are operating properly, go to next step.
  7. Check for excessive resistance, open or short (to ground or battery) in circuit No. 389 (Dark Green wire) between digital speedometer module and PCM Blue 80-pin connector C1, terminal No. 55. If circuit is not okay, go to next step. If circuit is okay, go to step 9).
  8. Repair excessive resistance, open or short (to ground or battery) in circuit No. 389 (Dark Green wire) between digital speedometer module and PCM connector C1. Recheck system operation.
  9. Check for poor connections at digital speedometer module. If connections are okay, replace digital speedometer module. Recheck system operation.
  10. Disconnect all speed-related components that are inoperative. Using DVOM, check voltage at circuit No. 389 (Dark Green wire) terminal of inoperative component and ground (if one or all components are inoperative, measure at any inoperative component's connector). Turn ignition switch to RUN position. Voltage should be 5 volts or more, but less than battery voltage. If voltage is as specified, go to step 12). If voltage is not as specified, go to next step.
  11. Check for excessive resistance, open or short (to ground or battery) in circuit No. 389 (Dark Green wire) between appropriate speed-related component and PCM. Repair as necessary and recheck system operation. If circuit is okay, check for internal shorts at vehicle speed input terminals. Repair as necessary and recheck system operation.
  12. Leave DVOM connected as specified in step 10). Ensure ignition switch is in RUN position. Rotate a drive wheel slowly by hand in forward direction. Voltage should vary between less than one volt and more than 2.5 volts. If voltage is as specified, go to next step. If voltage is not as specified, go to step 14).
  13. Check for poor connection at inoperative component. Repair as necessary and recheck system operation. If connection is okay, replace inoperative component. Recheck system operation.
  14. Reconnect all speed-related components. Disconnect PCM Blue 80-pin connector C1. Using DVOM, check voltage between PCM harness connector C1, terminal No. 55 (Dark Green wire) and ground. Turn ignition switch to RUN position. Voltage should be 5 volts or more, but less than battery voltage. If voltage is as specified, go to next step. If voltage is not as specified, go to step 16).
  15. Check for poor connection at PCM. Repair as necessary and recheck system operation. If connection is okay, diagnose and repair problem in PCM system. See appropriate TESTS W/CODES article in ENGINE PERFORMANCE section:
  16. Repair excessive resistance, open or short (to ground or battery) in circuit No. 389 (Dark Green wire) between inoperative component and PCM. Recheck system operation.
scientia non olet · About LEMON Manuals