What Does B1359 Mean?
B1359 indicates the Body Control Module (BCM) has detected an abnormal voltage or open/short circuit condition in the ignition run/accessory circuit. This circuit provides switched power to various vehicle systems when the ignition is in the RUN or ACC position. The BCM monitors this circuit to ensure proper voltage distribution and has identified a fault that prevents normal operation of accessories and systems dependent on this power source.
Common Causes
35%
Faulty ignition switch or worn ignition switch contacts causing intermittent or no power delivery to run/acc circuit
30%
Damaged, corroded, or loose wiring harness connections between ignition switch and BCM or fuse box
20%
Blown fuse or faulty relay in the ignition run/accessory power distribution circuit
10%
Failed or failing Body Control Module with internal circuit fault
5%
Short circuit to ground in run/acc power distribution wiring causing overcurrent condition
Diagnostic Steps
1
Step 1: Perform visual inspection of ignition switch connector and BCM connectors for corrosion, bent pins, or loose connections. Check all related fuses in the fuse box for the run/acc circuits using a test light or multimeter.
2
Step 2: Using a multimeter, backprobe the ignition switch connector and measure voltage at the run/acc output terminals with key in RUN and ACC positions. Expected reading: battery voltage (12-14V) in both positions, 0V in OFF position.
3
Step 3: If voltage is present at ignition switch but not at BCM input, trace wiring harness between switch and BCM checking for opens, shorts to ground, or high resistance (should be less than 0.5 ohms). Pay special attention to harness routing through steering column and firewall areas.
4
Step 4: If voltage reaches BCM correctly, check BCM ground circuits for integrity (should be less than 0.1 ohms to chassis ground). Monitor live data for BCM ignition status inputs while cycling key positions.
5
Step 5: Test ignition switch operation by measuring continuity through switch contacts in each position using a multimeter. Replace switch if contacts are intermittent or show high resistance (over 1 ohm).
6
Step 6: Clear codes and perform key cycle test (OFF-ACC-RUN-START cycle 10 times) while monitoring for code return. Verify all accessory and run circuits function properly before returning vehicle to service.
Estimated Repair Cost
$150 - $650
Parts + labor, varies by vehicle and location
B1359 indicates the Body Control Module (BCM) has detected an abnormal voltage or open/short circuit condition in the ignition run/accessory circuit. This circuit provides switched power to various vehicle systems when the ignition is in the RUN or ACC position. The BCM monitors this circuit to ensu...
The most common cause of B1359 (Ignition Run/Acc Circuit Failure) is: Faulty ignition switch or worn ignition switch contacts causing intermittent or no power delivery to run/acc circuit
Typical repair costs for B1359 range from $150 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle may experience intermittent loss of power to accessories, instrumentation, and safety systems like power windows, wipers, or gauges. While often still drivable, sudden loss of critical accessories could create unsafe conditions. Repair should be completed promptly to prevent being stranded or losing essential vehicle functions.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1359 to identify the root cause.
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Quick Info
Category
Body
System
Body Control and Electrical Power Distribution System
Difficulty
Type
Manufacturer
Recommended Tools
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