Code
B1652
HUMMER
B — Body
Loss of Keep Alive Memory (KAM)
AI status
Completed
Completed
100%
Causes
- Battery disconnected or recently replaced without proper procedure
- Low battery voltage or repeated deep discharges
- Loose, corroded or damaged battery terminals or ground connections
- Blown fuse or open circuit on the KAM supply or ground
- Faulty body control module (BCM) or other module that maintains KAM
- Wiring harness damage or connector issues on the KAM power/ground circuits
Symptoms
- Loss of radio presets, clock, seat/mirror memory or other personalized settings
- Security/immobilizer warnings or unexpected behavior
- Stored convenience feature settings reset to defaults
- Possible multiple related DTCs or communication errors after power interruption
- No obvious drivability symptoms in many cases (but module functions may be affected)
What to check
- Check battery state of charge and cranking/resting voltage
- Inspect battery terminals, cable ends and chassis grounds for tightness and corrosion
- Verify relevant fuses (body/retention/KAM feed) are intact
- Scan for additional DTCs and any module communication errors (U-codes)
- Check service history for recent battery disconnection, module replacement or reflash
- Measure KAM supply and ground at the BCM connector with key off (see diagnostic steps)
Signal parameters
- KAM supply voltage: nominal battery voltage (~12.6 V rested); should remain present with ignition off
- Retention current: typically very low (microamp to low milliamp range) with ignition off
- Voltage threshold: memory may be lost if battery falls well below normal (varies by module, often < 9–10 V)
- No pulses or intermittent voltage on KAM feed when vehicle is parked and key off
- Related CAN/serial messages present and stable when ignition on
Diagnostic algorithm
- Retrieve freeze frame and scan all modules; note any related DTCs (U-codes or other B-codes).
- Ask customer about recent battery service or accessories installed. If battery was disconnected, confirm proper procedure used.
- Check battery resting voltage. If low, charge or replace battery and clear code. Recheck after normal service voltage is restored.
- Visually inspect and clean battery terminals, cable ends and primary grounds. Tighten to spec and recheck.
- Verify fuses for the BCM/KAM supply. Replace any blown fuses and re-check for memory loss.
- With ignition off, backprobe the KAM power/retain pin at the BCM (refer to vehicle wiring diagram) and verify a steady battery voltage is present. Check for excessive current draw if voltage drops.
- Wiggle test harnesses and connectors at BCM while monitoring KAM supply for intermittent opens/shorts.
- Perform a parasitic draw test if memory loss is intermittent to identify aftermarket loads or faults.
- If wiring and power are good, check for software updates and re-flash/repair BCM per factory service instructions.
- If module fails to retain memory after verified good power and updated software, consider BCM replacement and follow immobilizer/programming procedures as required.
- After repairs, clear codes, verify retained settings after a key cycle and road test as needed.
Likely causes
- Battery was disconnected during service or replacement
- Battery voltage dropped below retention threshold (e.g., during cranking or due to a weak battery)
- Poor battery/ground connections causing intermittent KAM supply
- Blown fuse for memory/retain circuit
- Internal BCM fault or failed non-volatile memory
Fault status
Status
Loss of Keep Alive Memory detected — module reports KAM cleared or not retained. May occur after battery disconnect, low voltage, or module/wiring fault. Investigate battery, fuses, connections, and BCM.
Repair difficulty: Medium
Diagnostic time: 0.5 - 2.0 hours
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Repair manuals
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138
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