What Does B1847 Mean?
This code indicates the Body Control Module (BCM) has detected an abnormal voltage condition in the ignition tamper sensor circuit, specifically a short to battery voltage. The ignition tamper system monitors for unauthorized attempts to bypass or manipulate the ignition switch or cylinder. When the circuit voltage reads constant battery voltage instead of the expected reference voltage, the BCM sets this fault code.
Common Causes
45%
Damaged or chafed wiring harness causing short to power between ignition tamper sensor and BCM
30%
Failed ignition tamper sensor with internal short to power circuit
15%
Corroded or damaged connector terminals at ignition tamper sensor allowing cross-circuit contact
10%
Faulty Body Control Module with internal circuit failure causing false voltage detection
Diagnostic Steps
1
Step 1: Perform visual inspection of ignition switch area and all accessible wiring from ignition cylinder to BCM, looking for damaged insulation, chafing against sharp edges, melted wires, or pinched harnesses
2
Step 2: Disconnect ignition tamper sensor connector and measure voltage on sensor side of circuit with key on - should read 0V; if battery voltage present, locate and repair short to power in sensor or sensor wiring
3
Step 3: With sensor disconnected, measure resistance between tamper sensor signal wire and battery positive at BCM connector - should read infinite resistance (open circuit); any continuity indicates short to power in harness
4
Step 4: If wiring tests normal, connect known-good ignition tamper sensor and clear codes; if fault returns immediately, suspect BCM internal fault; if fault does not return, replace original tamper sensor
5
Step 5: After repairs, cycle ignition key multiple times and monitor live data for tamper circuit voltage stability; verify code does not return and anti-theft system functions properly
Estimated Repair Cost
$150 - $650
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected an abnormal voltage condition in the ignition tamper sensor circuit, specifically a short to battery voltage. The ignition tamper system monitors for unauthorized attempts to bypass or manipulate the ignition switch or cylinder. When the...
The most common cause of B1847 (Ignition Tamper Circuit Short To Battery) is: Damaged or chafed wiring harness causing short to power between ignition tamper sensor and BCM
Typical repair costs for B1847 range from $150 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle is generally safe to drive, but anti-theft protection may be compromised or non-functional. In some vehicles, this fault may prevent starting or cause intermittent no-start conditions requiring immediate attention.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1847 to identify the root cause.
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Quick Info
Category
Body
System
Anti-Theft/Security System
Difficulty
Type
Manufacturer
Recommended Tools
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