B1484

Code

FIAT B — Body

Brake pedal input signal open circuit between brake switch and stop lamps

Brand: FIAT

Type: B — Body

Views: UK: 2 EN: 11 RU: 5

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Broken or damaged wiring between brake switch and stop lamp circuit
Loose, corroded or disconnected connector at brake switch, lamp sockets, or BCM/BCU
Failed/incorrectly adjusted brake light switch
Blown fuse or fusible link supplying the brake switch/stop lamps
Corroded or shorted lamp sockets or bulbs
Poor ground at lamps or body control module

Symptoms

Brake lights do not illuminate when pedal is pressed or work intermittently
Cruise control or shift-interlock may be disabled (systems that monitor brake switch)
Brake warning or traction/ABS-related lights may be illuminated
Stored B1484 DTC and possible related communication or lamp-failure codes
Rear lamps behave erratically (one side works, the other does not)

What to check

Visually inspect brake light operation: have an assistant press the pedal while observing all stop lamps
Check relevant fuses and fusible links for the stop-lamp circuit
Inspect connectors at the brake light switch, stop lamp sockets and any inline connectors for corrosion, bent pins or disconnection
Check for aftermarket trailer harness or modifications that may affect wiring
Use a scan tool to view live data for the brake pedal/switch input to the BCM/BCU
Back-probe the switch and lamp connector to confirm presence/absence of voltage with pedal pressed and released

Signal parameters

With pedal released: brake switch output should read as open or ~0 V on circuits that switch +12 V to the lamps (depends on vehicle wiring)
With pedal depressed: brake switch output and stop lamp feed should be battery voltage ~11–14 V at the switch output and at the lamp connector
Continuity when switch closed: very low resistance (near 0 ohms through switch contacts); continuity between switch output pin and lamp socket center contact should be present
Typical stop lamp current draw: incandescent bulbs commonly 0.5–3 A each (LED modules lower); expect measurable current when lamps energize

Diagnostic algorithm

Step 1 — Confirm symptom and code: Retrieve B1484 with a scan tool and review freeze frame/live data while pressing the brake pedal.
Step 2 — Visual and fuse check: Inspect and test the stop-lamp fuse(s) and visually check bulbs and sockets for damage or corrosion. Replace as needed.
Step 3 — Verify lamp operation: Have an assistant press the pedal while you observe/verify voltage at each stop lamp socket.
Step 4 — Test brake switch: Back-probe the brake switch harness. With engine off, check continuity across the switch while actuating the pedal; with ignition on, verify expected voltage change when pedal pressed.
Step 5 — Continuity and wiring inspection: If the switch tests good, disconnect battery (for resistance checks), and perform a continuity test between the brake switch output pin and each stop lamp center contact. Wiggle harnesses to look for intermittent opens.
Step 6 — Inspect connectors and grounds: Clean and secure any corroded connectors or poor grounds. Repair or replace damaged connector terminals or harness sections.
Step 7 — Repair or replace: Replace the brake light switch, harness section, lamp socket or bulbs if found faulty. Repair open wires with solder and heat-shrink or OEM-style crimps and protective sleeving.
Step 8 — Re-test and clear codes: After repairs, reconnect battery, clear stored codes, confirm correct operation of brake lights and verify no reoccurrence of B1484 with a road test and scan-tool live data.
Step 9 — If persists: If wiring and components check good, suspect BCM/BCU input fault; consult wiring diagrams and consider module testing or replacement as a last step.

Likely causes

Failed or misadjusted brake light switch
Open/broken wire or connector at the switch harness or at a lamp socket
Blown fuse or corroded connector in the stop-lamp circuit
Damaged stop lamp (bulb or LED module) causing unexpected circuit behavior

Fault status

⚠️ Status

Open circuit detected in brake pedal input / stop lamp circuit (loss of continuity between brake switch and stop lamps).

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours

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