What Does B1355 Mean?
B1355 indicates the Body Control Module (BCM) has detected a fault in the ignition run circuit, which supplies power to various vehicle systems when the ignition is in the 'run' position. This circuit is critical for powering fuel pumps, ignition systems, engine control modules, and other essential components during vehicle operation. The BCM has identified either an open circuit, short to ground, excessive voltage drop, or loss of power in this circuit.
Safety Warning
Vehicle may experience no-start conditions, sudden engine shutdown while driving, or loss of critical systems like power steering and brakes. Do not drive the vehicle until fault is corrected as unexpected loss of power can create dangerous situations in traffic.
Common Causes
35%
Faulty ignition switch or worn ignition switch contacts causing intermittent or no power delivery to run circuit
30%
Damaged or corroded wiring harness between ignition switch and BCM, including broken wires or poor connections
20%
Failed or malfunctioning Body Control Module unable to properly monitor or control ignition run circuit
10%
Blown fuse or fusible link in the ignition run circuit power distribution
5%
Faulty ignition relay preventing proper power distribution to run circuit components
Diagnostic Steps
1
Step 1: Verify battery voltage is 12.4V or higher with engine off. Check all fuses related to ignition run circuit in both under-hood and interior fuse boxes using test light or multimeter. Document any blown fuses or fusible links.
2
Step 2: Using a digital multimeter, backprobe the ignition switch connector with key in RUN position and measure voltage output on the run circuit wire (typically 12V+). Compare readings with key in OFF, ACC, and RUN positions to verify proper switching function.
3
Step 3: Inspect wiring harness from ignition switch to BCM for physical damage, chafing, corrosion, or loose connections. Pay special attention to areas where harness passes through firewall or near moving components. Check for voltage drop across circuit using multimeter (should be less than 0.5V under load).
4
Step 4: Check ignition run relay operation by swapping with known good relay of same type, or test relay coil resistance (typically 70-100 ohms) and contact continuity when energized. Listen for audible click when ignition is turned to run position.
5
Step 5: If all upstream components test good, check BCM connector terminals for corrosion, bent pins, or damage. Measure voltage at BCM ignition run input pin with key in run position (should read battery voltage).
6
Step 6: Clear codes and perform operational test with key in run position. Monitor live data for ignition run circuit status through scan tool. If fault returns immediately, suspect BCM internal failure; if intermittent, suspect connection or switch contact issues.
Estimated Repair Cost
$100 - $800
Parts + labor, varies by vehicle and location
B1355 indicates the Body Control Module (BCM) has detected a fault in the ignition run circuit, which supplies power to various vehicle systems when the ignition is in the 'run' position. This circuit is critical for powering fuel pumps, ignition systems, engine control modules, and other essential ...
The most common cause of B1355 (Ignition Run Circuit Failure) is: Faulty ignition switch or worn ignition switch contacts causing intermittent or no power delivery to run circuit
Typical repair costs for B1355 range from $100 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle may experience no-start conditions, sudden engine shutdown while driving, or loss of critical systems like power steering and brakes. Do not drive the vehicle until fault is corrected as unexpected loss of power can create dangerous situations in traffic.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1355 to identify the root cause.
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Quick Info
Category
Body
System
Body Control and Ignition Power Distribution
Difficulty
Type
Manufacturer
Recommended Tools
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