What Does B1555 Mean?
This code indicates the Body Control Module (BCM) has detected an abnormal voltage or circuit condition in the ignition run/start power distribution circuit. The BCM monitors the ignition switch position signals and power feed circuits to verify proper voltage is present during RUN and START positions. This failure means the BCM is not receiving expected voltage or signal from the ignition switch circuit, which could prevent proper vehicle operation and starting functions.
Safety Warning
This is a critical issue that may prevent the vehicle from starting or cause sudden loss of electrical power while driving, creating dangerous situations. Vehicle should not be driven until repaired as it may stall unexpectedly or fail to restart.
Common Causes
35%
Faulty ignition switch or worn ignition switch contacts causing intermittent or no signal output
30%
Damaged, corroded, or loose wiring and connectors between ignition switch and BCM
20%
Blown fuse or faulty relay in the ignition run/start power supply circuit
10%
Failed Body Control Module (BCM) with internal circuit fault
5%
Low battery voltage or poor battery/ground connections affecting circuit operation
Diagnostic Steps
1
Step 1: Perform visual inspection of ignition switch wiring harness and connectors for obvious damage, corrosion, melted insulation, or loose connections. Check battery voltage with multimeter - should read 12.4V+ with engine off.
2
Step 2: Using multimeter, backprobe the ignition switch connector and verify voltage presence at RUN and START positions (typically 12V+). Compare readings to manufacturer specifications for proper voltage in each switch position.
3
Step 3: Check all ignition-related fuses and relays in the fuse panel using test light or multimeter. Verify fuse continuity and relay operation by swapping with known good relay of same type.
4
Step 4: Inspect BCM connector for corrosion, pushed-back pins, or moisture intrusion. Measure resistance between ignition switch output wire and BCM input terminal - should be less than 5 ohms with harness disconnected.
5
Step 5: Test ignition switch operation by monitoring continuity through all switch positions (OFF, ACC, RUN, START) using multimeter. Replace ignition switch if readings are inconsistent or out of specification.
6
Step 6: After repairs, clear codes and perform key cycle test (OFF-RUN-START sequence) 5-10 times while monitoring live data to verify BCM receives proper ignition signals without fault recurrence.
Estimated Repair Cost
$150 - $800
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected an abnormal voltage or circuit condition in the ignition run/start power distribution circuit. The BCM monitors the ignition switch position signals and power feed circuits to verify proper voltage is present during RUN and START positio...
The most common cause of B1555 (Ignition Run/Start Circuit Failure) is: Faulty ignition switch or worn ignition switch contacts causing intermittent or no signal output
Typical repair costs for B1555 range from $150 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
This is a critical issue that may prevent the vehicle from starting or cause sudden loss of electrical power while driving, creating dangerous situations. Vehicle should not be driven until repaired as it may stall unexpectedly or fail to restart.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1555 to identify the root cause.
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Quick Info
Category
Body
System
Ignition System / Body Control
Difficulty
Type
Manufacturer
Recommended Tools
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