LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Chevrolet >> 1990 >> APV >> Repair and Diagnosis >> Electrical >> Gauges >> Instrument Panel >> Testing >> Speedometer/Odometer Test >> Speedometer Is Inaccurate & ECM Code 24 Is Set
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Speedometer Is Inaccurate & ECM Code 24 Is Set

  1. Turn ignition on. Connect voltmeter between terminal "A" (Pink/White wire) of VSS buffer connector C1 and ground. If battery voltage is present, go to next step. If battery voltage is not present, repair open in Pink/White wire.
  2. Connect voltmeter between terminals "A" (Pink/White wire) and "B" (Black wire) of VSS buffer connector C1. If battery voltage is present, go to next step. If battery voltage is not present, repair open in Black wire.
  3. Turn ignition on. Place transaxle in Neutral. Raise drive wheels. Set voltmeter on AC scale. Measure voltage between terminals "A" (Purple wire) and "C" (Yellow wire) of VSS buffer connector C2 while rotating drive wheels by hand. If voltage varies between zero and one volt, check connectors C1 and C2. If connectors are okay, replace VSS buffer. If voltage remains at zero volt, check for open circuit in Yellow or Purple wire. If wire is okay, replace VSS.