B1351

Code

FIAT B — Body

Ignition key-in-start switch short to positive

Brand: FIAT

Type: B — Body

Views: UK: 6 EN: 6 RU: 5

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Page language: EN

Causes

Damaged or chafed wiring contacting battery positive or another fused B+ circuit
Corroded, pushed-out, or bridged pins in the ignition switch or harness connector
Internal failure of the ignition key-in/start switch (internal short)
Faulty or improperly installed aftermarket alarm, immobiliser or remote start wiring
Water intrusion or contamination in connector assemblies
Shorted splice, junction, or accessory wired to a constant B+ feed

Symptoms

Key-in or start indicator lamp illuminated incorrectly or continuously
Starter cranks unexpectedly or key removal/eject problems
Intermittent or no-crank condition depending on circuit behavior
Battery drainage or blown fuses related to the ignition circuit
Related warning lights or stored codes in the BCM or instrument cluster
Vehicle behaves as if key is in start position when it is not (intermittent)

What to check

Record stored freeze frame and freeze data, and note any additional DTCs in BCM/cluster.
Visually inspect ignition switch area, harness routing under steering column and firewall for damage, chafing, or repairs.
Inspect connectors for corrosion, melted pins, or signs of overheating; ensure locking tabs fully engaged.
Check fuses and fusible links related to ignition and instrument cluster for signs of shorting.
With ignition off, measure continuity between the key-in/start switch signal wire and battery positive to confirm short (should be open when key is not in the active position).
Backprobe the switch connector and verify voltage behavior with key out, key in (accessory), and key in start positions using a multimeter.

Signal parameters

Expected voltage at switch signal: ~0 V (open/ground) when key is removed or off; approximately battery voltage (~11–14 V) when key is in START/ON as designed.
Continuity: closed (low ohms) between the switch contact and B+ only in the proper key position; open (OL) otherwise.
No continuous battery voltage on the switch signal with ignition off—presence of B+ with key off indicates short to positive.
Resistance of switch contacts when closed: typically near 0 Ω (very low); when open: very high/OL.

Diagnostic algorithm

Safety first: park on level surface, engage parking brake, remove key, and disconnect negative battery terminal if you will be unplugging connectors or performing repairs that may short circuits.
Scan vehicle and record all stored DTCs. Note related network messages and module names reporting the fault.
Perform visual inspection of wiring from ignition switch to BCM and any intermediate junctions/splices under dash, steering column, and firewall; repair obvious damage.
With battery connected, backprobe the ignition switch harness connector (not the module) and measure voltage at the suspect signal wire with key out, key at ACC/ON, and key at START. Look for unexpected constant B+ with key out.
If constant B+ is present at the harness connector with the switch disconnected, the short is downstream (wiring to B+ or aftermarket splice) — trace and isolate by disconnecting harness sections or removing inline connectors until the short disappears.
If constant B+ is only present when the switch is connected, suspect internal short in the switch — remove and bench-test the ignition switch assembly and inspect its connector pins for bridging or damage.
Inspect and disconnect any aftermarket alarm/immobiliser/remote-start units; retest to see if code clears.
Repair wiring: replace or re-route chafed wires, repair splices properly with solder and heat-shrink or approved repair connectors, replace corroded connectors, or replace the ignition switch as needed.
After repair, clear the code with a scan tool, and perform repeated key position tests and a road-test/start-cycle to confirm the fault does not return.
If wiring and the switch check good but the code persists, consider module input fault—verify BCM grounds/power supplies and consult manufacturer procedures before replacing the control module.

Likely causes

Harness abrasion where it rubs on a metal panel or sharp edge, creating a short to a B+ source
Ignition switch connector pins pushed into each other or melted/bridged by heat
Aftermarket device tapping the ignition circuit tied to constant battery positive
Moisture-corroded connector producing conductive path to B+
Internal short inside the ignition switch assembly

Fault status

⚠️ Status

Ignition key-in/start switch circuit reports a short to positive (B+) — the control module detects battery voltage where it expects an open or switched signal.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours

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