Code
B2947
HUMMER
B — Body
Security System Sensor Power Circuit Low
AI status
Completed
Completed
100%
Causes
- Blown or poor fuse for the security/sensor power feed
- Weak or discharged vehicle battery, poor battery connections
- Open, short-to-ground, or high-resistance wiring in the sensor power circuit
- Corroded or loose connector at sensor(s) or BCM
- Faulty security sensor or module drawing excessive current
- Faulty BCM/security module or internal driver failure
Symptoms
- Security system warnings or fault indicator (instrument cluster)
- Alarm not arming/disarming properly or false alarms
- Interior motion/tilt sensors inoperative
- Related door/hood sensor faults or interior light/locking abnormalities
- Possible stored additional DTCs for related sensors or network communication
What to check
- Verify battery voltage at rest and with key ON (use a DMM)
- Inspect fuses and fusible links for the security/sensor power circuit
- Visually inspect wiring and connectors at BCM and security sensors for damage or corrosion
- Check continuity and resistance between battery positive (through fuse) and sensor power pin
- Check ground connections and measure continuity between sensor ground and chassis
- Use a scan tool to view live data, confirm which sensor(s) reported low power and clear codes to retest
Signal parameters
- Expected supply voltage at sensor with key ON: approx. 11–14 V (nominal 12 V system)
- Considered low if sensor supply is below about 9–10 V while key ON
- Open/high-resistance feed will show significant voltage drop between fused feed and sensor connector
- Ground continuity: chassis ground to sensor ground expected
- If sensor uses a regulated reference (some modules): expected reference ≈ 5 V — confirm against manufacturer data
Diagnostic algorithm
- Record freeze frame and related codes with a scan tool; note which sensor(s) are indicated.
- Check and verify battery condition and terminal connections. Recharge or replace weak battery before further testing.
- Inspect the fuse(s)/fusible link protecting the security/sensor power circuit. Replace any blown fuse and re-test.
- With ignition ON, measure voltage at the BCM fused output and at the reported sensor power pin. Compare values to battery voltage. Significant drop indicates wiring or connector issue.
- If low at sensor, disconnect the sensor connector and re-measure the fused feed at the harness side to determine if the short/low is in harness or caused by sensor.
- Check ground(s): measure continuity from sensor ground pin to chassis and to battery negative. Repair any high-resistance grounds.
- Inspect harness along routing between BCM and sensor for chafing, water intrusion, or connector corrosion. Repair damaged wiring or connectors.
- If wiring and connectors test OK, bench-test or substitute a known-good sensor to determine if the sensor is drawing excessive current.
- If a shorted driver inside the BCM is suspected (fused feed OK but BCM output low under load), consult repair manual for BCM tests; replacement/reprogramming of BCM may be required.
- After repairs, clear codes and perform functional tests and any required security system relearn procedures per manufacturer instructions.
Likely causes
- Blown fuse or fusible link on the sensor power feed
- Corroded/loose connector at a security sensor (door, hood, motion, tilt)
- Damaged wiring harness (pinched/chafed) causing short-to-ground or high resistance
- Weak battery or poor battery/ground connections under load
- Failed BCM output driver (less common)
Fault status
Status
Security system sensor power circuit voltage low. Check fuse, wiring, grounds, sensor and BCM.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
Repair manuals
Manual library for HUMMER
138
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