What Does B1558 Mean?
This code indicates the Body Control Module (BCM) has detected an abnormal short to ground condition in the ignition run/start circuit. The BCM monitors the voltage in the ignition switch circuit that supplies power to various vehicle systems during run and start positions. When the circuit voltage drops below expected parameters due to a short to ground, this code is triggered, potentially affecting starting capability and power distribution to multiple vehicle systems.
Safety Warning
Vehicle may experience no-start conditions, intermittent stalling, or loss of power to critical systems. Do not continue driving if vehicle exhibits starting problems or warning lights, as the short circuit could cause additional electrical damage or leave you stranded.
Common Causes
35%
Damaged or chafed wiring harness in the ignition switch circuit causing direct short to vehicle ground
30%
Faulty ignition switch with internal short to ground in run/start position contacts
20%
Corroded or moisture-damaged ignition switch connector causing intermittent ground fault
10%
Failed Body Control Module with internal circuit fault in ignition monitoring circuit
5%
Aftermarket accessory or remote starter installation causing parasitic ground in ignition circuit
Diagnostic Steps
1
Step 1: Perform visual inspection of ignition switch wiring harness from switch through bulkhead connector to BCM, looking for chafed insulation, pinched wires, corrosion, or damaged connectors. Pay special attention to areas where harness passes through metal grommets or near sharp edges.
2
Step 2: Using a digital multimeter, measure resistance from ignition switch run/start circuit wire (disconnected at BCM) to chassis ground with ignition off. Reading should be greater than 10k ohms; low resistance (under 100 ohms) confirms short to ground in harness or switch.
3
Step 3: Disconnect ignition switch connector and repeat resistance test from harness side to ground. If short disappears (high resistance), ignition switch is faulty. If short remains, fault is in wiring harness between switch and BCM.
4
Step 4: If harness tests good, inspect ignition switch connector terminals for corrosion, bent pins, or moisture intrusion. Clean terminals with electrical contact cleaner and apply dielectric grease.
5
Step 5: For intermittent faults, perform wiggle test on ignition switch harness while monitoring resistance to ground. Movement that causes resistance drop indicates wire damage location.
6
Step 6: After repairs, clear codes, cycle ignition through all positions multiple times, and verify code does not return. Confirm proper voltage present at BCM ignition circuit input (battery voltage in run/start positions).
Estimated Repair Cost
$150 - $650
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected an abnormal short to ground condition in the ignition run/start circuit. The BCM monitors the voltage in the ignition switch circuit that supplies power to various vehicle systems during run and start positions. When the circuit voltage ...
The most common cause of B1558 (Ignition Run/Start Circuit Short To Ground) is: Damaged or chafed wiring harness in the ignition switch circuit causing direct short to vehicle ground
Typical repair costs for B1558 range from $150 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle may experience no-start conditions, intermittent stalling, or loss of power to critical systems. Do not continue driving if vehicle exhibits starting problems or warning lights, as the short circuit could cause additional electrical damage or leave you stranded.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1558 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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