Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 85 (ENGINE CONTROLS - SELF-DIAGNOSTICS - 2.2L)DIAGNOSTIC TESTSDTC P0327: KNOCK SENSOR CIRCUITDIAGNOSTIC PROCEDURES
1999 GMC Forward Control 5.7 R, Automatic
Diagnostic Procedures
1999 GMC Forward Control 5.7 R, AutomaticSECTION Diagnostic Procedures
WARNING: This page is about a different car, the 2002 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
- 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 3 .
- 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 ECM. If voltage does not jump to more than 2 volts, problem is intermittent. See DIAGNOSTIC AIDS .
- 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, check for open in Gray wire between KS and ECM. If Gray wire is okay, replace ECM.
- Using DVOM, measure resistance between terminals at KS connector (ECM side). If resistance is 90-110 k/ohms, go to step 6 . If resistance is not 90-110 k/ohms, go to next step.
- Disconnect ECM connector J2. Measure resistance between ECM connector J2 terminal No. 18 (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 ECM, or faulty ECM.
- Start engine and let idle. Using DVOM on AC volt scale, measure voltage at KS terminal "B" 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 ECM. 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:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.