What Does B1671 Mean?
This code indicates that the Body Control Module (BCM) has detected a voltage reading from a battery module or auxiliary battery that is outside the expected operating range, either too high or too low. This typically affects vehicles with auxiliary battery systems, hybrid/electric vehicles with high-voltage battery modules, or systems with battery monitoring sensors. The BCM continuously monitors battery voltage levels and sets this code when readings fall outside manufacturer-specified parameters.
Common Causes
35%
Failed or weak auxiliary battery with internal cell degradation causing voltage instability
30%
Corroded, loose, or damaged battery terminal connections or cable wiring causing voltage drop or intermittent contact
20%
Faulty battery voltage sensor or monitoring module providing inaccurate readings to the BCM
10%
Defective charging system (alternator or DC-DC converter) causing overcharge or undercharge conditions
5%
BCM internal fault or corrupted software causing false voltage reading interpretation
Diagnostic Steps
1
Step 1: Perform visual inspection of all battery modules, terminals, cables, and ground connections for corrosion, damage, loose connections, or signs of overheating. Clean and tighten all connections as needed.
2
Step 2: Using a digital multimeter, measure the voltage at the battery module terminals with ignition off (should be 12.2-12.8V for 12V systems), then with engine running (should be 13.8-14.5V). Compare readings to manufacturer specifications and note any significant deviations.
3
Step 3: Access live data on the scan tool to compare actual battery voltage readings from the multimeter with the voltage values reported by the BCM/battery sensor. A difference greater than 0.5V indicates a faulty sensor or wiring issue.
4
Step 4: Perform a battery load test using a carbon pile tester or dedicated battery analyzer to verify the battery module can maintain voltage under load. A failing battery will show significant voltage drop below 9.6V during testing.
5
Step 5: Inspect charging system operation by measuring alternator output voltage and ripple with engine at 2000 RPM. Excessive ripple (over 0.5V AC) or improper voltage indicates alternator or voltage regulator failure.
6
Step 6: If all physical components test normal, check for BCM software updates or perform BCM reset/relearn procedures per manufacturer service information, then clear codes and verify repair with a test drive.
Estimated Repair Cost
$100 - $800
Parts + labor, varies by vehicle and location
This code indicates that the Body Control Module (BCM) has detected a voltage reading from a battery module or auxiliary battery that is outside the expected operating range, either too high or too low. This typically affects vehicles with auxiliary battery systems, hybrid/electric vehicles with hig...
The most common cause of B1671 (Battery Module Voltage Out Of Range) is: Failed or weak auxiliary battery with internal cell degradation causing voltage instability
Typical repair costs for B1671 range from $100 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle may be drivable but could experience electrical system failures, loss of power steering, accessory malfunctions, or sudden stalling if battery voltage becomes critically low. Repair within a few days to avoid being stranded or causing damage to sensitive electronic modules.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1671 to identify the root cause.
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Quick Info
Category
Body
System
Electrical System / Body Control
Difficulty
Type
Manufacturer
Recommended Tools
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