B1356: Ignition Run Circuit Open
Diagnostic trouble code B1356 indicates an open circuit in the ignition run circuit. This means the powertrain control module (PCM) or body control module (BCM) has detected a loss of voltage or a break in the circuit that powers various components when the ignition switch is in the Run position. This circuit supplies power to essential electronic systems, and a failure can prevent accessories from working, cause starting issues, or keep the control modules from receiving the voltage signal needed to activate emissions and safety systems, triggering this manufacturer-specific fault code.
1. Commonly Affected Makes
2. Most Common Causes
- Faulty ignition switch with burned contacts
- Open, broken, or short-to-ground wiring in the run circuit
- Damaged ignition circuit fuse or relay
- Loose, corroded, or bent pins in the ignition switch connector
- Faulty body control module (BCM) or PCM
3. Symptoms You Will Notice
- Engine cranks but won't start
- Dashboard warning lights or accessories not working with ignition on
- No power to radio, windows, or other electrical components in Run position
4. Step-by-Step Diagnosis
Check the ignition run circuit fuse and relay; replace if blown or faulty
Inspect the ignition switch connector for corrosion, damage, or loose pins
Test for voltage at the ignition switch output in the Run position
Check continuity of the run circuit wiring from the switch to the BCM/PCM
If wiring and switch check out, test the BCM and PCM for internal faults
5. Frequently Asked Questions
Is it safe to drive?▼
No, this is a high-severity issue. Driving with an open ignition run circuit can cause unexpected stalling, loss of power to critical systems, or a no-start condition, posing a safety risk.
How much does it cost to fix?▼
Repair costs vary widely: a faulty ignition switch may cost $150-$400 including labor, while wiring repairs range $100-$300. If the BCM or PCM needs replacement, expect $500-$1,200 or more.