Code
B1422
HUMMER
B — Body
Device Power Moding Malfunction
AI status
Completed
Completed
100%
Causes
- Low or unstable battery voltage or poor battery connections
- Blown fuse or tripped relay on the device power circuit
- Open, shorted, corroded or damaged wiring harness or connectors
- Poor ground connection at device or control module
- Faulty controlled device (actuator/motor/module) drawing abnormal current
- Faulty body/control module or internal power stage failure
Symptoms
- Device fails to enter commanded power mode or remains in a limp/safe mode
- Intermittent or erratic device operation (stutters, surges, or won’t operate)
- One or more interior warning messages or indicator lamps related to the affected system
- Loss of functionality for the affected system (reduced performance)
- DTC stored in memory and possibly repeated on key cycles
What to check
- Read DTCs and freeze-frame data with a capable scan tool; record occurrence conditions
- Check battery voltage and state-of-charge with engine off and during cranking; verify battery terminals are clean and tight
- Inspect fuses and relays for the affected circuit; replace suspect fuses and retest
- Visually inspect wiring and connectors at the device and control module for corrosion, damage, water intrusion, or loose pins
- Back-probe power and ground pins at the device while operating and while commanded through modes; verify stable battery voltage and solid ground
- Measure current draw of the device (if safe/possible) to detect overcurrent or no current conditions
Signal parameters
- Battery supply voltage at device power pin: typically ~12.0–14.5 V (engine running)
- Ground resistance: less than 0.5 ohm preferred between device ground and chassis/battery negative
- Device control signal: PWM duty cycle, frequency or commanded state as specified in service data (verify with oscilloscope or lab scope)
- Device current draw: compare measured amperage to factory specification for that device
- CAN/LIN bus: error counters, message presence and frequency; expected CAN message IDs and periodicity per service manual
- Module supply/ignition sense voltages: present when ignition is in the commanded state
Diagnostic algorithm
- Capture DTC, freeze-frame and live data with a scan tool. Note when the fault set (operating conditions).
- Verify battery condition and terminal connections. Recharge or replace a weak battery before further testing.
- Inspect relevant fuses and relays; replace any blown or suspect items and attempt to re-create the fault.
- Visually inspect harnesses/connectors at the device and control module for corrosion, bent pins, water intrusion or physical damage.
- With connector connected, back-probe and measure power and ground at the device while commanding different power modes. Look for voltage drop, intermittent loss or excessive voltage variation.
- Measure device current draw during operation and compare to specification to identify a short or internal device failure.
- Check communications (CAN/LIN) for errors and verify the control module and device exchange expected messages. Repair bus faults if present.
- Wiggle-test wiring and connectors while observing live data and voltages to reproduce an intermittent fault.
- If wiring, supply and communication are OK, consult service information for module diagnostics — reprogram or reflASH software if a known calibration issue exists.
- If module-level testing indicates internal failure, replace the failed device or control module and clear codes. Retest system operation and confirm fault does not return.
- Note: Follow OEM safety precautions. For vehicles with high-voltage systems, isolate and follow high-voltage procedures per the service manual.
Likely causes
- Battery voltage below specified threshold during command (low battery or parasitic draw)
- Intermittent connector contact or corrosion at device power/ground pins
- Short to ground or short to battery on device power modulation circuit
- Internal failure of the device’s power-stage or MOSFET/transistor
- Control module detecting abnormal current or incorrect feedback from device
- Failed fuse or relay feeding the device power moding circuit
Fault status
Status
Control module detected invalid or out-of-range power mode behavior for the controlled device; commanded mode not achieved or abnormal current/voltage detected. DTC B1422 logged.
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
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Repair manuals
Manual library for HUMMER
138
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