B1356
Ignition Run Circuit Open
Body Network/Communication Ignition Circuit Control 🟢 Low — Fix at next service
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What This Actually Means
In plain language — no jargon

The ignition run circuit that powers accessories when the key is in the 'Run' position has an open or broken connection. Think of it like a light switch that won't stay connected to the power supply.

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Symptoms You May Notice
3 known symptoms for this code
Dashboard lights and accessories not functioning with key in Run position
Engine cranks but won't start or runs erratically
Radio, climate control, or other accessories intermittently lose power
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Embedded Systems Insight
What the ECU/ECM is actually computing

The ECU monitors voltage presence on the ignition run circuit, expecting a stable 12V supply when the ignition switch is in Run mode. If the ECU detects zero or low voltage where it should be present, it sets this fault code indicating an open circuit condition.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
Ignition Run Voltage 12-14V when key in Run position Below 10V or absent voltage
Circuit Resistance Less than 0.5 ohms Infinite resistance (open circuit)
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Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Ignition switch connector
Inspect and reseat the ignition switch connector; corrosion or loose pins are common causes.
2
Ignition run relay
Test the run relay with a multimeter; if faulty, replace it in the relay panel.
3
Ignition run wiring harness
Check the wiring between ignition switch and fuse box for breaks, pinches, or corrosion; repair or replace damaged sections.