B1372

Code

Other B — Body

Illuminated Entry Relay Circuit Open

Brand: Other

Type: B — Body

Views: UK: 23 EN: 38 RU: 27

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Blown fuse for interior lighting or relay feed
Faulty illuminated entry (courtesy) relay
Broken or disconnected wiring (open) in relay coil or contact circuit
Corroded or loose connector at relay or BCM
Faulty door ajar switch or door module wiring
Faulty body control module (BCM) or relay driver

Symptoms

Interior courtesy/dome lights do not illuminate when doors are opened
Interior lights do not come on with remote unlock
Dome lights only work on manual switch but not door-activated
Stored B1372 fault in BCM and possible related lamp warnings

What to check

Verify vehicle battery voltage is within normal range (12–14.5 V).
Scan BCM for B1372 and any related codes, note freeze-frame data.
Visually inspect fuses and relay for damage or melting; check relay socket and wiring harness for broken wires or corrosion.
Check for voltage at relay supply terminal and for control signal at the relay coil terminal when the illuminated entry is commanded.
Measure continuity from relay socket to BCM and to door switches; wiggle wiring to reproduce fault.
Swap relay with identical known-good relay (if available) to confirm relay failure.

Signal parameters

Battery supply to relay: approx. battery voltage (12–14.5 V) at the relay feed terminal.
Relay coil control: should see 0 V (inactive) and ~battery voltage or ground switching when commanded depending on design (verify with wiring diagram).
Relay coil resistance: continuity / low ohms (typically tens to a few hundred ohms) indicating coil not open.
Switch contact: continuity through contact when relay is energized; open when de-energized.
Ground continuity: low resistance from relay ground terminal to chassis ground.

Diagnostic algorithm

Retrieve and record codes with a scan tool; clear codes and attempt to reproduce to confirm persistent fault.
Visually inspect fuse(s) and relay for the illuminated entry circuit; replace blown fuse and retest.
Remove relay and inspect socket and pins for corrosion, damage, or an open circuit; check for battery voltage at the relay feed terminal with ignition ON.
Command the illuminated entry (open a door or unlock with remote) while measuring voltage at the relay coil control terminal. If no control signal is present, trace the control wire back to the BCM or door module.
Check continuity of the coil circuit and contact circuit between relay socket and BCM/lighting load. Repair any open wires, broken pins, or poor grounds.
Swap in a known-good identical relay to verify relay functionality. If relay swap cures the fault, replace the failed relay.
If wiring and relay are confirmed good but no control signal is present, test the BCM output driver for shorts/opens per manufacturer procedure. Replace or reprogram BCM only after confirming wiring/relay integrity.
After repairs, clear codes, verify proper operation of illuminated entry function in multiple conditions (doors open/close, remote unlock), and re-scan for codes.

Likely causes

Open / disconnected wiring at relay socket (most common)
Failed relay coil or internal contact open
Blown fuse supplying the relay
Connector corrosion or poor pin contact at relay or BCM
BCM driver output failed (less common)

Fault status

⚠️ Status

Illuminated entry relay circuit open — the control module detected an open circuit in the relay/relay wiring for the interior courtesy lighting. Interior lights may not operate automatically with door open or remote unlock.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours