Code
B3147
HUMMER
B — Body
Passenger Unlock Switch Circuit Low
AI status
Completed
Completed
100%
Causes
- Damaged or shorted wiring in passenger door harness
- Faulty passenger unlock switch (mechanical or internal short)
- Corroded or loose connector/terminal at switch or BCM
- Water intrusion in door switch or connector
- Faulty Body Control Module (BCM) or input circuit
- Blown fuse or poor power/ground to related circuits
Symptoms
- Passenger door unlock switch unresponsive or behaves incorrectly
- Driver-side controls unlock other doors but passenger switch does nothing
- Intermittent unlock operation of passenger door
- DTC B3147 stored and may illuminate a message on dash (depending on model)
- Keyless entry or remote unlock works but in-door switch does not
What to check
- Read and record freeze frame and related B-codes with a scan tool
- Inspect passenger door switch connector for corrosion, bent pins, and water intrusion
- Visually inspect wiring harness along door jamb and hinge area for chafing or pinches
- Check fuses and general power/ground integrity for BCM and door module circuits
- Backprobe the passenger unlock switch connector and monitor signal with switch operated
- Wiggle test wiring while observing scan tool or DVOM for intermittent changes
Signal parameters
- Nominal inactive (open) signal: pulled high — approximately 5–12 V depending on vehicle module (verify with service manual)
- Nominal active (switch pressed) signal: near 0 V (grounded) — typically
- Open-circuit resistance: very high/infinite when open; closed switch resistance: near 0–5 Ω
- If the BCM uses a 5 V logic input, inactive ~5 V; if 12 V reference, inactive ~10–12 V. Confirm with vehicle spec.
Diagnostic algorithm
- Connect a capable scan tool, read DTCs and freeze frame data. Note any other related door/body codes. 2) With ignition on, backprobe the passenger unlock switch connector. Observe voltage with switch at rest and while operating the switch. Compare to expected signal parameters. 3) If signal is permanently low, disconnect the switch. If the voltage returns to expected (pulled-up) level when disconnected, suspect the switch or short to ground; if not, suspect wiring or BCM input. 4) Inspect the connector and wiring from door switch to body harness, paying special attention to the hinge/jamb area for chafed wires. Repair any damaged wiring with proper splices or replacement. 5) If wiring appears intact, test continuity from the switch pin to the BCM input (with connectors disconnected) and check for shorts to ground. 6) Clean and secure connectors; replace the passenger unlock switch if it fails direct bench or in-vehicle tests. 7) If wiring and switch test good, verify BCM grounds and power. If all inputs/power/ground are good and the input still reads low, consider BCM/input module fault and consult factory service information for module testing or replacement. 8) Clear codes and perform functional test to confirm repair.
Likely causes
- Broken chafed wire at door hinge (common flex point) shorted to ground
- Switch contacts internally shorted or stuck closed due to contamination
- Connector pins pushed out, corroded, or bent at passenger door switch
- Moisture in door mirror/switch area causing a low/grounded signal
- Aftermarket alarm or wiring spliced into unlock circuit causing a short
Fault status
Status
Passenger Unlock Switch Circuit Low — low voltage or short-to-ground detected on passenger door unlock switch input to BCM/input module. May cause in-door unlock function to fail or behave intermittently.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
Repair manuals
Manual library for HUMMER
138
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