Electrical Diagnosis

Systematic electrical diagnosis procedure for the 2023 Chevrolet Bolt EUV using scan tools and multimeter testing to identify faults in the high-voltage and low-voltage electrical systems.

Warnings

Tools required

Parts

• 12V battery terminal protector spray × 1 — Use OEM specification

Preparation

1. Park vehicle on level surface and engage parking brake
2. Ensure vehicle is OFF (not in READY mode) and key fob is at least 15 feet away
3. Open hood and locate 12V battery in front compartment passenger side
4. Connect scan tool to OBD-II port under driver side dashboard
5. Document all customer concerns and symptoms in detail
6. Perform visual inspection of vehicle for obvious damage, modifications, or aftermarket accessories
7. Check for any pending service bulletins or recalls related to reported symptoms

Procedure

1. 1

   Initial Scan and Code Retrieval
   Power on scan tool and establish communication with vehicle. Select 2023 Chevrolet Bolt EUV from vehicle menu. Perform comprehensive scan of all modules including HPCM2 (High Voltage Battery Control Module), TPIM (Traction Power Inverter Module), BECM (Body Electronics Control Module), and all accessory modules. Document all DTCs with freeze frame data, occurrence counts, and current/history status. Note any communication failures or missing modules.
2. 2

   12V Battery System Test
   Using multimeter, measure 12V battery voltage at battery terminals. Should read 12.4-12.8V with vehicle off. Check for corrosion, loose connections, or damage at both terminals. Test battery load capability if voltage is borderline (below 12.4V). Inspect 12V battery cables for damage, particularly the ground cable to body and engine ground strap connections. The Bolt EUV uses the high-voltage system to charge the 12V battery, so low 12V voltage can indicate DC-DC converter issues.
3. 3

   Verify High-Voltage System Status
   Using scan tool, navigate to HPCM2 data display. Monitor high-voltage battery pack voltage (should be 300-400V depending on state of charge), battery temperature, cell voltage delta (should be less than 0.1V between highest and lowest cells), and isolation resistance. Check for any high-voltage interlocks open status. Review high-voltage contactor status - both main positive and negative contactors should show proper operation history. Do NOT disconnect 12V battery yet if high-voltage system diagnostics are needed.
   ⚠️Do not touch any orange high-voltage cables during this inspection. View data through scan tool only.
4. 4

   Disconnect 12V Battery
   If low-voltage circuit testing is required and high-voltage diagnostics are complete, disconnect negative terminal of 12V battery using 10mm wrench. Wait minimum 2 minutes for all modules to power down completely. This de-energizes the high-voltage system by opening contactors and allows safe testing of low-voltage circuits. Cover negative terminal to prevent accidental reconnection.
5. 5

   Verify High-Voltage De-Energization
   If diagnosis requires accessing high-voltage components, put on insulated high-voltage gloves. Using CAT III rated multimeter set to DC voltage (minimum 600V range), measure voltage at high-voltage service disconnect located in rear cargo area under access panel. Verify voltage is below 5V DC. Check that all orange service plugs are properly seated. Verify high-voltage interlock loop continuity if interlock fault codes are present.
   ⚠️Always verify zero voltage before touching any high-voltage component, even with service disconnect removed.
6. 6

   Low-Voltage Circuit Testing
   Based on DTCs and symptoms, identify specific circuits requiring testing. Using wiring diagrams, locate connectors and test points for suspected circuits. Perform voltage drop tests, continuity tests, and resistance measurements as directed by diagnostic flowcharts. Common circuits include: charging port communication lines, temperature sensors, cooling pump circuits, brake system pressure sensors, and body control circuits. Document all measurements and compare to specifications in service information.
7. 7

   Connector and Ground Inspection
   Inspect all connectors in circuit being diagnosed for corrosion, bent pins, moisture intrusion, or backing-out terminals. Pay special attention to connectors under vehicle exposed to road debris and moisture. Check ground points G100 (behind left headlamp), G101 (left front frame rail), and G201 (right front frame rail) for tightness and corrosion. The Bolt EUV is particularly sensitive to poor ground connections affecting CAN bus communication.
8. 8

   Module Power and Ground Verification
   For any module with communication faults or internal failures, verify module has proper power and ground. Reconnect 12V battery temporarily if needed for powered tests. Check for battery voltage at module power supply pins and less than 0.1V at ground pins with module connected and operating. Measure voltage drop during operation if module reports intermittent issues.
9. 9

   CAN Bus Network Testing
   If multiple module communication codes are present, test CAN bus network integrity. Measure CAN High and CAN Low voltage at DLC (Data Link Connector) - should show 2.5V each with key on, no communication. During active communication, should toggle between approximately 2.0-3.5V. Check for 60 ohm resistance between CAN High and CAN Low with all modules connected and scan tool disconnected. Resistance outside 55-65 ohm range indicates network fault.
10. 10

    Component-Specific Testing
    Based on diagnostic path identified from codes and circuit tests, perform component-specific testing. For sensors, verify resistance values and signal voltages match specifications. For actuators, command activation through scan tool bi-directional controls and verify operation. For switches, test continuity in both positions. Document all findings and compare to normal operating parameters in service information.
11. 11

    Thermal Event Recording Review
    Using scan tool, review HPCM2 thermal event history and battery pack performance data. Check for any high-temperature events, thermal limiting activation, or reduced power events. Review DC fast charging history for any incomplete sessions or faults. These records can reveal intermittent issues not present during static testing.
12. 12

    Final System Scan and Documentation
    Reconnect 12V battery if disconnected. Ensure all connectors and components disturbed during testing are properly secured and reinstalled. Clear all diagnostic codes if testing is complete and root cause identified. Perform final complete system scan to verify no new codes were introduced during diagnosis. Test drive vehicle if necessary to verify repair or reproduce intermittent symptom. Document all test results, measurements, and diagnostic conclusions in repair order.

Reassembly

1. Ensure all electrical connectors are fully seated with positive lock engagement
2. Verify all access covers and panels removed during diagnosis are reinstalled properly
3. Reconnect 12V battery negative terminal and apply terminal protector spray
4. If high-voltage service disconnect was removed, reinstall and verify positive engagement
5. Verify all tools and equipment are removed from vehicle

Verification

• Turn vehicle to ON position and verify all warning lights function normally during bulb check
• Activate vehicle to READY mode and confirm no warning lights remain illuminated
• Verify dash displays correct range and battery charge status
• Perform final scan with all systems - should show no active DTCs related to diagnosed issue
• Test all affected systems for proper operation (charging, climate control, drive functions, etc.)
• For intermittent issues, review diagnostic strategy with customer and recommend monitoring period
• Provide customer with detailed explanation of findings and any recommended repairs

Related trouble codes on this vehicle

Codes that commonly send this job to the bay — tap one for symptoms, causes, and diagnostic steps.

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