B2251

Code

Other B — Body

Parklamp Output Relay Driver Circuit Failure

Brand: Other

Type: B — Body

Views: UK: 22 EN: 28 RU: 25

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Page language: EN

Causes

Blown fuse or faulty parklamp relay
Open or shorted wiring between module and relay
Corroded or loose relay/socket connectors
Faulty body control module (BCM) or relay driver transistor
Short to battery or ground on the driver circuit
Aftermarket modifications or water intrusion in lighting circuits

Symptoms

Park lamps (side/parking lights) inoperative or intermittent
Instrument cluster lamp or message indicating lighting fault
Other body electrical oddities if BCM shares circuits
Possible blown fuses after repeated attempts to operate lamps

What to check

Verify stored DTCs (B2251 and any related codes) and freeze frame with scan tool
Visual inspection of fuses, relay, relay socket, connectors, and wiring for damage or corrosion
Check condition and seating of relay; inspect for water or corrosion in socket
Measure battery voltage at relay power terminal with ignition on
Backprobe relay coil terminals to verify control signal from BCM when lamps are commanded
Check continuity and resistance between BCM driver pin and relay socket

Signal parameters

Supply voltage at relay common: ~11–14.5 V with ignition ON
Relay coil resistance (typical): ~50–200 ohms (varies by relay) — coil current roughly 0.06–0.3 A
Control output from module: switches to ground (0 V) or high-impedance when active; inactive = open/high Z or pulled high
No-load voltage on control pin when inactive: near battery voltage via pull-up or high impedance depending on design
If PWM control used: duty cycle varies, frequency typically 20–200 Hz (model dependent)

Diagnostic algorithm

Connect a scan tool, confirm B2251 and note any related codes (lamp circuits, BCM, fuses). Record freeze-frame data.
Perform a visual inspection: fuses, relay, relay socket, wiring harness, lamp connectors for corrosion, damage, or water intrusion.
With ignition ON, measure battery voltage at the relay power terminal. Replace blown fuse or repair power feed if low/missing.
Remove relay, inspect socket for corrosion and continuity. Check coil terminals for continuity (typical coil resistance 50–200 ohms).
Backprobe the relay coil control wire at the socket. Command parklamps ON with scan tool and observe control pin: it should be driven to ground (0 V) or show expected PWM. If no change, suspect BCM driver or open circuit.
Verify continuity between the module driver pin and the relay socket control terminal. Repair any open or high-resistance sections.
Check for shorts: measure resistance from control wire to battery positive and to chassis ground. Repair short to B+ or ground if present.
Swap in a known-good relay. If relay swap restores operation, replace faulty relay and clear codes.
If wiring and relay are good but control still abnormal, perform module output testing per manufacturer procedure. Consider bench-testing or replacing BCM only after verifying connector/pin wiring and grounds.
After repairs, clear codes, cycle ignition, and verify parklamp operation and that B2251 does not reset. Road test as needed.

Likely causes

Bad relay or relay socket contact causing intermittent connection
Damaged or chafed wiring harness near lamp or relay
Corroded connector at relay or lamp assembly
BCM driver output failed (internal transistor short or open)
Blown fuse supplying relay coil

Fault status

⚠️ Status

Parklamp output relay driver circuit fault detected. The module has identified abnormal behavior (open, short, or excessive current) on the parklamp relay driver circuit. Check relay, wiring, and module output.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-1.5 hours