Code
B1438
HUMMER
B — Body
IPC High Voltage Output Overcurrent to IPM
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UK: 11
EN: 17
RU: 18
AI status
Completed
Completed
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Causes
- Short circuit in high-voltage output wiring (phase-to-phase or phase-to-ground)
- Failed or shorted IPM (internal transistor/IGBT failure)
- External load (motor, inverter, heater, compressor) drawing excessive current
- Damaged insulation on HV cables or connector corrosion
- Faulty current sensor or measurement circuit
- Blown or tripped HV fuse/circuit breaker
Symptoms
- Malfunction or loss of the high-voltage load controlled by the IPM (e.g., drive motor, traction inverter function reduced)
- Adaptive or limp mode, reduced vehicle performance
- Illuminated malfunction indicator lamp(s) or HV warning lamp
- HV system disables or trips repeatedly after restart
- Burning smell or heat at connectors (in severe cases)
What to check
- Retrieve DTC(s) and freeze frame data with a scan tool; record operating conditions when fault occurred
- Check for additional related codes (body, network, powertrain, HV subsystem)
- Visual inspection of HV wiring, connectors, and IPM for damage, melting, discoloration, or corrosion
- Verify HV service interlocks and fuses/circuit breakers status
- Confirm vehicle is in a safe, powered-down state before any HV work; use PPE and follow manufacturer HV isolation procedure
- Measure continuity/resistance of HV outputs to detect shorts to ground or between phases (only after HV is isolated)
Signal parameters
- Recorded overcurrent event flag from IPC/IPM (fault bit set)
- High-voltage output current: exceeds manufacturer maximum threshold (spec varies by vehicle; consult service data)
- Pack voltage: normal operating voltage present when fault recorded (e.g., hundreds of volts depending on model)
- IPM temperature and internal diagnostics (overtemp or internal fault codes)
- Duty cycle/PWM command from IPC to IPM: present but current draws exceed commanded values
Diagnostic algorithm
- Read and record all DTCs and freeze frame data with a capable scan tool. Note frequency and conditions of occurrence.
- Follow manufacturer high-voltage safety procedures: disable HV system, remove service disconnect, wear PPE. Do not probe live HV circuits without appropriate training/equipment.
- Perform a visual inspection of HV harnesses, connectors, and the IPM for signs of arcing, heat damage, or contamination.
- Check fuses and HV circuit breakers for open or tripped condition. Reset if allowed by manufacturer and monitor.
- With HV isolated, check continuity and insulation resistance of the IPM output harness to each phase and to chassis ground to detect shorts.
- Disconnect IPM output connectors and isolate external loads (motors/compressors). Restore HV per procedure and confirm whether overcurrent reoccurs to determine if IPM or external load is source.
- If overcurrent follows the IPM with loads disconnected, suspect internal IPM failure—verify with manufacturer bench test or replacement.
- If overcurrent disappears with the IPM isolated and reappears when a specific load is reconnected, inspect/bench-test that load.
- Inspect and if necessary test/replace current sensor or measurement circuitry if readings are inconsistent with measured current.
- Clear codes, perform controlled functional test/road test while monitoring HV current, voltage, and IPM status. If fault persists, follow manufacturer repair procedures (component replacement and reprogramming as required).
Likely causes
- Short or damage in the high-voltage harness between IPC and IPM
- Failed IPM with internal short
- External load (motor/compressor) has a short or mechanical seizure
Fault status
Status
High-voltage output overcurrent to the IPM detected. IPM output may be disabled and HV system performance limited. Service by qualified technicians required.
Repair difficulty: Hard
Diagnostic time: 2.0-5.0 hours
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