Code
B1356
ALFA ROMEO
B — Body
Ignition on circuit
AI status
Completed
Completed
100%
Causes
- Blown ignition-related fuse
- Faulty ignition switch
- Faulty ignition (IG) relay
- Open, short to ground or short to battery in wiring harness for IGN_ON circuit
- Poor or corroded connector or terminal at switch, relay or module
- Faulty body control module / instrument cluster / ECU input stage
Symptoms
- No-crank or no-start condition on some key positions
- Dash/instrument cluster not powering up or flickering when key ON
- Intermittent loss of vehicle electrical functions when key is ON
- Possible inability to record other control unit faults
- Battery drain or parasitic draw if ignition circuit stuck ON
What to check
- Read freeze frame and related codes with a diagnostic scanner; note key position when fault set
- Check battery voltage (resting and with key ON) and battery terminals for good contact
- Inspect fuses and relays related to IGN/IGNITION/IG circuits
- Visual inspection of ignition switch, steering column connectors, fusebox and associated wiring for damage or corrosion
- Backprobe the IGN_ON feed at the relay/switch and target module while operating the ignition to verify voltage and continuity
- Wiggle harnesses and connectors while monitoring voltage to detect intermittent faults
Signal parameters
- Ignition ON feed voltage: approx. battery voltage (nominal 12.0–14.5 V) with key in ON/Run
- Ignition OFF: feed should be near 0 V (or within the vehicle's defined off threshold)
- Cranking: voltage may drop but should remain >9–10 V at starter engagement
- Continuity: low resistance (typically
- Intermittent faults: voltage may flicker or drop quickly under wiggle test or vibration
Diagnostic algorithm
- Connect a scan tool, read all stored codes and freeze-frame data; note the key position and battery voltage when the code was recorded.
- Check battery condition and terminals; ensure good supply before proceeding.
- Inspect fuses and relay(s) for the ignition feed; swap a known-good identical relay if suspect.
- Visually inspect wiring from ignition switch to fusebox/relay and to the affected module(s); look for damage, pinched areas, corrosion, or aftermarket splices.
- Backprobe the ignition feed at the relay output and at the receiving module; verify battery voltage is present with key in ON and that it disappears with key off as expected.
- Perform a wiggle test on steering column harnesses, switch connectors and fusebox while watching voltage or live data for intermittent changes.
- If an open or high resistance is found, isolate by testing continuity between ignition switch output and module connector; repair or replace damaged wiring/connectors.
- If the wiring and fuses/relays are good but the feed is absent at the switch, test and replace the ignition switch.
- If feed is present to the switch/relay but missing at the control module input, check the module connector; repair wiring or replace the module only after confirming input pin problems.
- After repairs, clear codes, verify stable ignition feed under all key positions and perform a road test to confirm the fault does not return.
Likely causes
- Intermittent connector making/breaking under vibration (common at steering column)
- Damaged insulation chafing to ground causing intermittent short
- Failed ignition switch contacts not supplying the IG feed
- Corroded fusebox terminal or relay socket
- Aftermarket alarm/immobilizer wiring interfering with ignition feed
Fault status
Status
The vehicle control module has detected an abnormal condition on the Ignition ON circuit (missing, low, high, or intermittent voltage). Verify ignition feed, fuses/relays, wiring and related modules before replacing control units.
Repair difficulty: Medium
Diagnostic time: 1.0 - 2.5 hours
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