B1492

Code

ALFA ROMEO B — Body

Ignition cylinder sensor open circuit

Brand: ALFA ROMEO

Type: B — Body

Views: UK: 5 EN: 6 RU: 3

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Page language: EN

Broken or disconnected wiring between ignition cylinder sensor and control module
Corroded/damaged connector or terminal at the sensor
Failed ignition cylinder/position sensor (internal open)
Water ingress or contamination of connector or sensor
Poor ground or lost reference voltage from the module
Aftermarket alarm/immobilizer wiring damage or improper installation

DTC B1492 stored (MIL may or may not be illuminated)
Vehicle may not recognize key or may fail immobilizer checks, causing crank/no-start or intermittent starting
Ignition key position functions (accessory/on/start) may be intermittent or nonfunctional
Possible related steering-lock or security system faults
Intermittent faults that sometimes clear after moving the steering wheel or key

Read and record freeze-frame and related security/immobilizer codes with a diagnostic scanner
Check battery voltage (low battery can cause spurious faults)
Inspect ignition-cylinder sensor connector for corrosion, water, bent terminals or deposits
Visually inspect wiring harness along steering column for abrasion, pinches or previous repair sections
Backprobe sensor connector with key turned to different positions and observe signal and reference voltages
Check continuity between sensor connector and the receiving module connector with harness disconnected

Sensor types used: Hall-effect (digital switching or variable 0–5 V) or resistive/position sensor (variable voltage) depending on model
Expected signal: valid reference voltage present (typically a switched or 5 V reference) and a corresponding changing signal when key is rotated
Open-circuit indication: signal line reads OL/infinite resistance or no voltage change when key is moved
When digital Hall type: signal toggles between ~0 V and ~5 V during rotation; when analog: voltage varies smoothly within 0–5 V range

Connect a diagnostic scanner and confirm B1492 and any related codes. Note whether codes are current or history.
Inspect visually: ignition lock barrel, connector, and harness for damage, corrosion or water entry. Repair obvious issues.
Check battery condition and charging; weak battery can affect modules—restore normal voltage before further tests.
With ignition off, disconnect sensor connector and inspect terminals for continuity, corrosion, pushed-out pins or broken wires.
Backprobe with ignition ON (follow safety and manufacturer procedures): verify reference/5 V supply and ground presence at the connector. Record voltages.
Rotate key while observing signal wire: verify expected change (digital switch toggling or analog voltage change). If no change, check continuity from sensor signal pin to the receiving module connector.
Measure resistance across sensor if service data provides values; open circuit will show very high/OL resistance. If unknown, compare to a known-good sensor or consult factory data.
Perform a wiggle test on harness while observing live data for intermittent connections. Repair/replace wiring or connector as needed.
If wiring and connectors are good and signals are absent or out of spec, replace the ignition cylinder sensor/lock barrel assembly per manufacturer procedure.
After repairs, clear codes, re-test key operation and drive/immobilizer functions, and confirm code does not return.

⚠️ Status

Ignition cylinder sensor open circuit detected — no continuity or missing signal from the ignition barrel position sensor.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours

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