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 P1273-P1536DTC P1441DTC P1441: EVAP SYSTEM FLOW DURING NON-PURGE (4.3L, 5.0L & 5.7L "C", "G" & "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.
- Connect EVAP Pressure/Purge Diagnostic Station (J-41413) to EVAP service port. Ensure vacuum gauges on diagnostic station is zeroed. Turn rotary switch on diagnostic station to PURGE position. Start engine. Monitor vacuum gauge on diagnostic station. If vacuum reading is -15 in. H2O, go to next step. If vacuum reading is not -15 in. H2O, see DIAGNOSTIC AIDS .
- Turn ignition off. Disconnect EVAP purge solenoid harness connector. Turn ignition on, engine off. Connect test light between battery voltage and EVAP purge solenoid connector terminal "B". If test light illuminates, go to next step. If test light does not illuminate, go to step 6.
- Turn ignition off. Disconnect VCM harness connector. Turn ignition on, engine off. Connect test light between battery voltage and EVAP purge solenoid connector terminal "B". If test light illuminates, go to next step. If test light does not illuminate, go to step 7.
- Repair short to ground in EVAP purge valve driver circuit. After repairs, go to step 8.
- Replace EVAP canister purge solenoid. After replacing solenoid, go to step 8.
- Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
- Using a scan tool, select DTC, CLEAR INFO. Perform SERVICE BAY TEST for EVAP system. After performing tests, go to next step.
- Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTCs are displayed, go to applicable DTC test. If no additional DTCs are set, system is okay.
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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.