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 MANUALSCHEVROLET1999CHEVY EXPRESS G1500, VAN CARGO, 5.7 RREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROL SYSTEM - TESTS W/CODES - DTC P1537-U1193DTC P1605DTC P1605: HVAC SERIAL DATA CIRCUIT (3.1L "W" BODY - CENTURY ONLY)DIAGNOSTIC PROCEDURES
1999 Chevrolet Chevy Express G1500, Van Cargo, 5.7 R
Diagnostic Procedures
1999 Chevrolet Chevy Express G1500, Van Cargo, 5.7 RSECTION 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.
- Using scan tool, attempt to select HVAC data. If HVAC data can be displayed, go to next step. If HVAC cannot be displayed, go to step 4.
- Turn ignition off. Disconnect HVAC controller and PCM harness connector. Check serial data circuit for open between HVAC controller and PCM. Repair as necessary. After repairs, go to step 6. If circuit is okay, go to next step.
- Check serial data circuit for poor connection at HVAC controller. Repair as necessary. After repairs, go to step 6. If circuit is okay, go to next step.
- Check serial data circuit for poor connection at PCM. Repair as necessary. After repairs, go to next step. If connection is okay, diagnose A/C-heater system. See appropriate A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.
- Review and record scan tool FAILURE RECORDS data. Clear DTC(s). Operate vehicle within the FAILURE RECORDS conditions. Using scan tool, monitor SPECIFIC DTC INFO for DTC P1605. If scan tool indicates that DTC P1605 failed, repeat step 2. If scan tool does not indicate that DTC P1605 failed, 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.