B1302

Code

FIAT B — Body

Accessory timer relay circuit

Brand: FIAT

Type: B — Body

Views: UK: 23 EN: 128 RU: 20

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Blown fuse for accessory/timer circuit
Faulty accessory timer relay or relay socket
Open or shorted wiring harness to the relay (broken conductor, chafing, pinched insulation)
Corroded or loose connector terminals at relay or timer module
Poor or missing ground at relay or control module
Faulty body control module (BCM) or accessory timer module

Symptoms

Accessories that should be timed (radio, windows, interior lights) do not operate or do not remain powered after ignition off
Accessories do not switch on at all
Intermittent accessory operation
Parasitic battery drain or accessories remaining on when they should turn off
DTC stored and possibly related body electrical warnings

What to check

Read and record freeze frame and all stored codes with a diagnostic scanner
Visually inspect fuse(s) related to accessory/timer circuit for blown fuse or poor fit
Inspect relay and relay socket for corrosion, pushed pins, burn marks or melting
Check wiring harness along routing for damage, chafing, pinches, or exposed conductors
Verify good engine/chassis ground and ground at BCM/timer module
Check battery voltage at rest and with accessory on (no excessive voltage drop)

Signal parameters

Battery supply to relay: approx. battery voltage (~12.0–14.5 V) with ignition/accessory ON
Control/coil terminal when energized: close to battery voltage on switched side; coil feed typically battery voltage on one side and ground or control on the other
Coil resistance (relays vary): typically tens to a few hundred ohms (example range 20–300 Ω) — check OEM spec if available
Ground continuity to chassis: near 0 Ω (ideal
Timer/BCM control signal: switches between ground and supply or outputs a switched 12 V — should change state when commanded via scanner (duration depends on vehicle feature, seconds to minutes)

Diagnostic algorithm

Connect a diagnostic scanner, read and record B1302 and any other stored codes; note freeze-frame data and ignition/accessory state.
Visually inspect fuse box, fuses, relay, relay socket and associated wiring for obvious damage, corrosion or loose connectors; repair as needed.
With ignition OFF, disconnect battery negative when working on connectors if performing repairs; otherwise be careful with live testing.
Identify relay terminals (coil feed, coil ground/control, common, normally open/closed). Check for battery feed at the common/coilh-feed terminal with ignition in required position. Expect ~battery voltage.
With ignition/accessory ON, command accessory timer via scanner (if supported) and measure voltage at the relay control terminal. Verify it switches as commanded.
Measure coil resistance between the coil terminals; compare to generic expectations or OEM spec. If infinite/open, coil is open—replace relay.
Check continuity between relay ground and battery negative (
If wiring or connector fault suspected, back-probe and perform wiggle tests to reproduce the symptom; use a lab multimeter to find intermittent opens/shorts.
If relay and wiring check good, test or bench the accessory timer/BCM output: command the timer and verify output at module connector. If module does not command output but has correct inputs, suspect module failure.
After repairs or replacements (fuse, relay, wiring repair, BCM/timer module if required), clear DTCs, then cycle ignition and reacquire scanner data to confirm the fault does not return and accessories operate normally.
If intermittent, perform road or bench tests to reproduce and confirm reliability; monitor for parasitic draw if accessories remain on.

Likely causes

Blown fuse or bad relay
Corroded/loose connector at relay or timer module
Open or short in wiring between BCM and relay
Failed accessory timer/BCM

Fault status

⚠️ Status

Accessory timer relay circuit — open/short or incorrect signal detected

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours

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