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Home >> Isuzu >> 1989 >> I-Mark RS, 2D Hatchback >> Repair and Diagnosis >> Engine Performance >> System >> Tests W/Codes - EFI >> Diagnostic Circuit Check >> Code 24 - VSS Circuit >> Notes

Code 24 - VSS Circuit: Notes

NOTE: Test numbers refer to test numbers on diagnostic chart.
  1. Code No. 24 will be set when speed sensor indicates less than 5 MPH, engine speed is between 1500-4400 RPM, coolant temperature is greater than 185°F (85°C), MAP is less than 7 psi (.5 kg/cm2 ) and conditions exist for at least 3 seconds. This test uses "Scan" tester to verify VSS operation.
  2. This checks for the presence of ECM supplied 12-volt signal, which is monitored by ECM for pulses, indicating VSS operation.
  3. Circuit No. 439 is ignition feed that supplies operating power to VSS. If this circuit is open, circuit No. 437 will remain at 12 volts at all times.
  4. Circuit No. 450 supplies ground path for VSS operation. If circuit No. 450 is open, VSS cannot pulse circuit No. 437 to ground.
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