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 DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROL SYSTEM - TESTS W/CODES - DTC P0352-P0452DTC P0443DTC P0443: EVAP PURGE SOLENOID CONTROL CIRCUIT (4.8L, 5.3L & 6.0L "C" & "K" SERIES)DIAGNOSTIC PROCEDURES
1999 GMC Forward Control 5.7 R, Automatic
Diagnostic Procedures
1999 GMC Forward Control 5.7 R, AutomaticSECTION Diagnostic Procedures
- Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS INTRODUCTION article. After performing OBD system check, go to next step.
- Turn ignition on, with engine off. Using scan tool, command EVAP solenoid on and off. If solenoid turns on and off as commanded, go to next step. If solenoid does not turn on or off when commanded, go to step 5.
- Turn ignition off. Disconnect PCM harness connector C2. Connect a fused jumper wire to control circuit at PCM harness connector. Turn ignition on, with engine off. Using DVOM, set DVOM to 40-amp scale. Check current draw from solenoid control circuit in PCM harness connector to ground for 2 minutes. If current draw is less than 0.75 amp (but not zero), see DIAGNOSTIC AIDS . If current draw is not less than 0.75 amp, go to next step.
- Turn ignition off. Disconnect EVAP solenoid. Using DVOM, check resistance from solenoid control circuit in PCM harness connector and ground. If resistance is not infinite, go to step 12. If resistance is infinite, go to step 10.
- Turn ignition off. Disconnect EVAP solenoid. Connect test light between solenoid harness connector terminals. Warm engine to normal operating temperature. Operate engine at idle. Using scan tool, command solenoid on and off. If test light turns on and off with each command, go to step 8. If test light does not turn on and off with each command, go to next step.
- Connect test light ground and probe ignition feed circuit in solenoid harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 11.
- Turn ignition off. Reconnect EVAP solenoid. Disconnect PCM harness connector. Turn ignition on. Connect a fused jumper wire between ground and PCM harness connector, solenoid control circuit. If solenoid operates, go to step 9. If solenoid does not operate, go to step 10.
- Check connections at EVAP solenoid. Repair as necessary. After repairs, go to step 14. If connections are okay, go to step 12.
- Check connections at PCM. Repair as necessary. After repairs, go to step 14. If connections are okay, go to step 13.
- Repair faulty EVAP solenoid control circuit. After repairs, go to step 14.
- Repair faulty EVAP solenoid ignition feed circuit. After repairs, go to step 14.
- Replace EVAP solenoid. After replacing solenoid, go to step 14.
- Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
- Using scan tool, select DTC, CLEAR INFO function. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter this DTC. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2.
- Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, go to applicable DTC test.
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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.