1992 Isuzu Impulse RSFACTORY OEM SERVICE PROCEDURE

Code 24 (1.6L Turbo) - VSS Circuit: Notes

The ECM provides battery voltage to the Vehicle Speed Sensor (VSS), located in instrument panel. The VSS alternately grounds white wire, which toggles the voltage high and low. This pulsed signal is used by the ECM to determine vehicle speed.

NOTE: Test numbers refer to test numbers on diagnostic chart.
  1. Code 24 sets if vehicle speed equals 0 MPH when:
    • Engine speed is between 2400-4400 RPM.
    • TPS is at zero percent (closed throttle).
    • MAP reads low voltage with high vacuum (low load condition).
    • All conditions are met for 5 seconds.
  2. These conditions are met during a road load deceleration. Disregard Code 24 that sets when drive wheels are not operating.
Factory Service Tools

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.

When to See a Mechanic

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

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