1. What is P0650?

P0650 is a Diagnostic Trouble Code indicating a Malfunction Indicator Lamp (MIL) Control Circuit Malfunction. The MIL (commonly called the Check Engine Light) is controlled by the PCM, which sends voltage signals to turn the lamp on/off when trouble codes are stored or cleared.

In Chevrolet Silverado 1500, P0650 triggers when the PCM detects an open, short, or irregular voltage in the MIL circuit. This means the Check Engine Light may not illuminate when it should—hiding critical engine or transmission issues from the driver.

2. Common Causes in Chevrolet Silverado 1500

• Burnt-Out MIL Bulb – Filament failure (common in 2014–2020 models with incandescent bulbs); LED bulbs rarely fail but may have driver circuit issues.
• Damaged MIL Wiring – Frayed or broken wires between the dashboard and PCM (often from dashboard removal or rodent damage).
• Corroded Electrical Connectors – Oxidation in the MIL connector (prevalent in Silverados used in humid or salty environments).
• Faulty PCM Output Driver – Internal PCM component failure preventing voltage delivery to the MIL (more common in 2019–2023 models).
• Blown Fuse – Burned-out fuse in the instrument cluster circuit (check fuse box label for "MIL" or "Instrument Cluster").
• Dashboard Module Malfunction – Failed instrument cluster control module disrupting MIL communication.

3. Key Symptoms

Silverado 1500 owners with P0650 often notice these symptoms, which can hide other issues:

• Check Engine Light (MIL) fails to illuminate when ignition is turned to "On" (should light for 2–3 seconds during bulb check).
• MIL does not turn on even when other trouble codes are present (confirmed via diagnostic scan).
• Intermittent MIL operation (flickers or turns off randomly).
• Instrument cluster warning lights (e.g., battery, oil pressure) working normally—only MIL is affected.
• PCM stores P0650 even after other codes are cleared.
• In rare cases: dim or overly bright MIL when it does illuminate.

4. Diagnostic Steps with UR800

The UR800 simplifies P0650 diagnosis by testing circuit integrity and isolating the fault source:

• 1. Bulb Check Test: Turn ignition to "On" (engine off) – UR800 will verify if MIL illuminates during the 2–3 second self-test. No light = bulb or circuit issue.
• 2. Code Scan & Verification: Scan for P0650 and related codes (P0651/P0652 for circuit high/low). Confirm if other codes exist but aren’t triggering the MIL.
• 3. Circuit Voltage Test: Use UR800’s multimeter to measure voltage at the MIL connector (should read 12V when PCM commands the light on; 0V when off).
• 4. Continuity Check: Test wiring between MIL and PCM – resistance should be <1Ω. Higher readings indicate damaged wires or corroded connectors.
• 5. PCM Output Test: Use UR800’s "Actuation Test" to command the PCM to turn the MIL on/off. No response = PCM or driver circuit failure.
• 6. Fuse Inspection: UR800’s electrical system scan can identify blown fuses; cross-verify with physical fuse box check.

Case Example: 2017 Silverado 5.3L with P0650 – UR800 showed 0V at MIL connector during actuation test. Continuity check revealed a broken wire under the dashboard (from previous stereo installation). Repairing the wire fixed the issue.

5. Fixes & Execution

Repair strategies for Silverado 1500 P0650 based on diagnostic findings:

• Replace MIL Bulb: - Remove dashboard trim panel (use plastic pry tools to avoid scratches). - Access instrument cluster; locate MIL bulb socket (check Silverado service manual for position). - Replace with OEM-spec bulb (incandescent: 194/7440; LED: compatible with Silverado’s voltage). - Reassemble and verify with UR800 bulb check.
• Repair Wiring/Connectors: - Identify damaged wires via UR800 continuity test; mark affected sections. - Cut damaged portions, strip 1/4" insulation, and splice with heat-shrink butt connectors. - Clean corroded connectors with electrical contact cleaner; apply dielectric grease to prevent future oxidation.
• Replace Blown Fuse: - Locate instrument cluster fuse box (driver’s side dash or under hood). - Identify "MIL" or "Instrument Cluster" fuse (typically 7.5A–10A). - Replace with fuse of identical amperage; test with UR800 voltage check.
• Address PCM Issues: - Use UR800 to check for PCM software updates (available for 2019+ models). - If output driver failure is confirmed, professional PCM repair/replacement is required. - Reprogram PCM after replacement using UR800’s coding function.
• Instrument Cluster Repair: - For faulty dashboard modules, remove cluster and inspect for burnt components. - Replace damaged solder joints or circuit board traces (professional repair recommended). - Reinstall and perform communication test with UR800.

6. Repair Costs

• DIY Diagnosis with UR800: $0 (avoids $80–$150 dealer diagnostic fee)
• MIL Bulb Replacement: $5–$20 (part) + $50–$100 (professional labor)
• Wiring/Connector Repair: $10–$30 (parts) + $70–$150 (labor)
• Fuse Replacement: $2–$10 (part) + $20–$50 (labor if professional)
• PCM Repair/Replacement: $200–$500 (part) + $150–$300 (labor/programming)
• Instrument Cluster Repair: $100–$300 (professional service)
• Total Professional Repair: $100–$800+ (varies by cause)

7. Preventive Maintenance

• Inspect MIL operation monthly during ignition start (should illuminate for 2–3 seconds).
• Use UR800 quarterly to scan for pending codes that might not trigger the MIL.
• Protect wiring harnesses during dashboard work (avoid pinching or cutting wires).
• Apply dielectric grease to electrical connectors annually (especially in humid climates).
• Check instrument cluster fuses during routine oil changes.
• Update PCM software every 2 years using UR800 to prevent compatibility issues.

8. Frequently Asked Questions

9. Summary

P0650 in Chevrolet Silverado 1500 indicates a Malfunction Indicator Lamp (MIL) control circuit issue, caused by faulty bulbs, wiring damage, blown fuses, or PCM problems. Symptoms include a non-functional Check Engine Light, which can hide other critical issues.

The UR800 diagnostic tool simplifies repairs by identifying root causes (bulb vs. wiring) and verifying fixes. Prompt resolution ensures you’re alerted to other engine issues, while regular maintenance (monthly MIL checks, connector care) prevents recurrence.