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 DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROL SYSTEM - TESTS W/CODES - INTRODUCTIONSELF-DIAGNOSTIC SYSTEMDLC DIAGNOSIS OR NO SCAN TOOL DATA4.0L
1999 Chevrolet Chevy Express G1500, Van Cargo, 5.7 R
DLC Diagnosis Or No Scan Tool Data: 4.0L
1999 Chevrolet Chevy Express G1500, Van Cargo, 5.7 RSECTION 4.0L
NOTE:
Perform On-Board Diagnostic (OBD) system check after completing any repairs. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK .
- Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . After performing OBD system check, go to next step.
- Check all PCM power and ground connections and circuits. Repair as necessary. If connections and circuits are okay, go to next step.
- Ensure battery is fully charged. Using DVOM, measure voltage between DLC battery feed circuit and DLC ground circuits. See appropriate wiring diagram in WIRING DIAGRAMS article. Voltage reading for both circuits should be 10 volts or greater. If voltage is as specified, go to step 7. If voltage is not as specified, go to next step.
- Using DVOM, measure voltage between ground and DLC battery feed circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. Voltage reading should be 10 volts or greater. If voltage is as specified, go to next step. If voltage is not as specified, go to step 6.
- Repair open in DLC ground circuit that had low or no voltage. After repairs, go to step 7.
- Repair open or short to ground in DLC battery feed circuit. Replace open fuse as necessary. After repairs, go to next step.
- Turn ignition on. If scan tool displays PCM data, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . If scan tool does not display PCM data, go to next step.
- Connect scan tool to another vehicle and check for proper operation. If scan tool operates properly, go to next step. If scan tool does not operate properly, go to step 13.
- Reconnect scan tool to original vehicle and enter fluid life information. Turn ignition off and wait 30 seconds. Disconnect PCM harness connector C1. Using DVOM, measure resistance of class 2 serial data circuit between PCM and DLC. See appropriate wiring diagram in WIRING DIAGRAMS article. If resistance is greater than 5 ohms, go to step 11. If resistance is not greater than 5 ohms, go to next step.
- Disconnect Remote Accessory Control (RAC) module harness connector. Using DVOM, measure resistance of DLC class 2 serial data circuit to ground. See appropriate wiring diagram in WIRING DIAGRAMS article. If resistance is less than 10,000 ohms, go to step 12. If resistance is 10,000 ohms or greater, go to step 14.
- Repair open in class 2 serial data circuit.
- Repair short to ground in class 2 serial data circuit.
- Replace faulty scan tool.
- Reconnect PCM harness connectors. Check for PCM data with RAC module disconnected. If scan tool displays PCM data, go to step 17. If scan tool does not display PCM data, go to next step.
- Check connections at PCM harness connector C1. Repair as necessary. If connections are okay, go to next step.
- Replace PCM. Perform PCM relearn procedures.
- Replace RAC module.
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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.