Diagnostic Procedures

2001 Chevrolet Chevy Express G2500, Van Cargo Extended, 5.7 R, L31/KL8SECTION Diagnostic Procedures
WARNING: This page is about a different car, the 2002 Saturn LW200, 2002 Saturn L200, and 2002 Saturn L100. However, it is still accessible from the selected car via links, so may be relevant.
  1. Start engine and let idle. Using scan tool, monitor KS NOISE while slowly accelerating engine between idle and wide open throttle. If voltage varies from around 0.2 volt to more than one volt when engine is accelerated, go to next step. If voltage does not vary from around 0.2 volt to more than one volt, go to step Β 3 .
  2. Let engine idle. Using scan tool, monitor KS NOISE. If voltage at idle ever jumps to more than 2 volts, repair short to voltage in Dark Blue wire between KS and PCM. If voltage does not jump to more than 2 volts, problem is intermittent. See DIAGNOSTIC AIDSΒ  .
  3. Turn ignition off. Disconnect knock sensor. Using DVOM, measure resistance between KS connector terminal "B" (Gray wire) and ground. If resistance is less than 2 ohms, go to next step. If resistance is not less than 2 ohms, repair open in Gray wire between KS and PCM or faulty PCM.
  4. Using DVOM, measure resistance between terminals at KS connector (PCM side). If resistance is 90-110 k/ohms, go to step Β 6 . If resistance is not 90-110 k/ohms, go to next step.
  5. Disconnect PCM connector J2. Measure resistance between PCM connector J2 terminal No. 64 (Dark Blue wire) and ground, then between terminals at KS connector. If continuity exists in either test, repair Dark Blue wire shorted to ground or shorted to Gray wire. If continuity does not exist in either test, repair open in Dark Blue wire between KS and PCM, or faulty PCM.
  6. Start engine and let idle. Using DVOM on AC volt scale, measure voltage at KS terminal "A" while accelerating from idle to wide open throttle. If AC voltage varies from a few millivolts at idle to more than 100 millivolts at wide open throttle, check connector at KS. If connector is okay, replace PCM. If AC voltage does not vary from a few millivolts at idle to more than 100 millivolts at wide open throttle, replace KS.
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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.