Code
B1390
OPEL
B — Body
Comfort Closing Circuit Low Voltage
Views:
UK: 3
EN: 6
RU: 6
AI status
Completed
Completed
100%
Causes
- Weak or discharged vehicle battery
- Poor battery connection or corroded terminals
- High resistance or poor ground at module or chassis ground point
- Blown fuse or faulty comfort‑closing relay
- Damaged wiring or connector (short to ground, open, high resistance)
- Faulty comfort‑closing module or body control module (BCM)
Symptoms
- Comfort closing (automatic window/sunroof/lock) fails or is intermittent
- One or more doors/windows do not respond to comfort close command
- DTC B1390 stored and may reappear after clearing
- Other body electrical functions may show faults or degraded performance
- Possible warning messages or chimes when attempting comfort close
What to check
- Read and record stored DTCs and freeze frame data; clear DTCs and reattempt to reproduce
- Measure battery voltage at rest and while operating the comfort close function
- Inspect battery terminals and main grounds for corrosion, tightness, and continuity
- Check fuses and relays related to comfort closing and body control module
- Visually inspect wiring and connectors for damage, water ingress, or corrosion
- Measure voltage at the comfort closing module power supply pin and ground while actuating
Signal parameters
- Battery/resting voltage: typically ~12.4–12.8 V (fully charged); below ~11.5 V may cause faults
- Operating voltage during comfort close: should remain above ~11.0 V; significant drops (
- Supply pin voltage at BCM/module: expected ~11–14.5 V when ignition/accessory or comfort function active
- Ground resistance at module: should be low (generally
- Module quiescent current: low (mA range); actuator peak currents vary by motor (typically up to several amps peak)
Diagnostic algorithm
- Retrieve codes and freeze frame. Note battery voltage recorded with the fault.
- Verify battery state of charge and health. If low, fully charge or replace battery and retest.
- Clean and tighten battery terminals and main negative ground. Recheck voltage and attempt comfort close.
- Inspect and test relevant fuses and relays; replace any suspect components.
- With a DVOM, measure voltage at the comfort closing module supply pin and ground while commanding the function. Look for excessive voltage drop.
- Check continuity and resistance of ground and power feeding the module. Repair any high‑resistance connections.
- Command individual actuators (windows/sunroof) and measure current draw. If an actuator draws excessive current, isolate and repair/replace that actuator.
- Inspect harnesses and connectors for corrosion, water entry or damaged wires; repair solder/joint or replace connector as needed.
- If wiring and actuators are good and supply voltages are correct but fault persists, consider module reset/reprogramming per OEM procedure; if still unresolved, evaluate module replacement.
- After repairs, clear codes and perform multiple comfort close cycles to confirm fault does not return.
Likely causes
- Low battery state of charge or poor battery condition
- Loose/corroded battery terminals or poor ground at body control module
- Blown fuse or failing relay in comfort closing supply circuit
- Damaged wiring harness or pin corrosion at module connector
- Stuck/shorted window/sunroof actuator causing excessive current draw
- Intermittent BCM power supply or internal module fault (less common)
Fault status
Status
Comfort closing circuit supply voltage below manufacturer threshold detected during comfort‑closing request. Comfort closing may be disabled until supply voltage and circuit integrity are restored.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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