Code
B1390
HUMMER
B — Body
Device Voltage Reference Input Circuit Malfunction
AI status
Completed
Completed
100%
Causes
- Open, shorted or corroded wiring in the reference voltage circuit
- Loose, corroded, or damaged connector at the sensor or control module
- Failed sensor or device drawing abnormal current
- Blown fuse or faulty power/ground for the reference source
- Faulty body control module / reference voltage source
- Intermittent connection due to chafed harness, pin push-out, or moisture
Symptoms
- Related device or sensor inoperative or intermittent
- Warning light or message on the dash
- Stored B1390 trouble code and possibly other electrical codes
- Erratic or incorrect readings from the affected sensor
- Vehicle systems dependent on that sensor may disable or go to limp mode
What to check
- Scan for B1390 and any additional stored/related codes and read freeze frame/live data
- Visually inspect connectors, pins and wiring for corrosion, damage or pin push-out
- Verify battery voltage and main ground integrity before testing circuits
- Backprobe the reference terminal at the device and at the module while engine/accessory power is on
- Check fuse(s) supplying the reference and replace if blown
- Wiggle harness and connectors while monitoring voltage to reproduce intermittent faults
Signal parameters
- Expected reference voltage typically ~5.0 V (common acceptable range 4.75–5.25 V)
- Open circuit will often read 0 V at the device reference pin
- Short to battery may read >5.5 V or close to battery voltage
- Short to ground will pull the reference near 0 V or significantly below the nominal value
- Signal should be a steady DC with minimal ripple; high noise indicates poor regulation or grounding
Diagnostic algorithm
- Retrieve all related codes and freeze frame data with a scan tool. Note affected subsystem and conditions.
- Visually inspect wiring, harness routing, connectors and related fuses for obvious damage or corrosion.
- With ignition on, measure reference voltage at the device reference pin and at the supplying module/backprobe point. Compare to spec (≈5 V).
- If reference is correct at module but not at device, check continuity of reference wire and inspect for opens/shorts. Repair damaged wiring.
- If reference is low or noisy at the module, check module ground integrity and module supply voltages (battery voltage, key-on power).
- Disconnect the device. If the reference returns to normal with device disconnected, the device is likely shorting the reference and should be replaced.
- If wiring and device check good but problem persists, consider module reprogramming/replacement per factory procedure.
- After repairs, clear codes and perform functional test and road test to confirm the fault does not return. Re-scan to verify.
Likely causes
- Damaged or disconnected connector at the affected device (most common)
- Open or shorted reference wire between device and module
- Bad ground at module or device
- Failed reference voltage regulator inside control module
- Failed device/sensor that pulls the reference out of range
Fault status
Status
Device voltage reference input circuit is out of specification or not present. Check reference supply, wiring, connectors and the supplying module.
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
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Repair manuals
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