B2546

Code

Other B — Body

System Power Relay Circuit Failure

Brand: Other

Type: B — Body

Views: UK: 21 EN: 28 RU: 24

AI status

Completed

ready

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Page language: EN

Causes

Blown fuse(s) feeding the relay or powered module
Failed or sticking system power relay (coil or contacts)
Open, shorted, corroded, or damaged wiring in relay control or output circuit
Poor or missing ground at relay or module
Faulty body control module (BCM) / engine control unit (ECU) driver output
Aftermarket accessory modification or poor repair affecting the circuit

Symptoms

Related system(s) do not power up or are intermittent (e.g., infotainment, HVAC, body functions)
One or more system warning lights or DTC stored
No voltage at relay switched terminal when relay should be energized
Battery drain if relay contacts stuck closed
Relays clicking repeatedly or not clicking when commanded

What to check

Scan tool: read the B2546 fault, freeze frame, and relevant live data or actuator tests
Check battery voltage (should be ~12.4–12.8 V at rest, ~13.5–14.8 V when running)
Visually inspect relay, fuse(s), relay socket and wiring for corrosion, burn, or damage
Wiggle test connectors and harness while observing symptoms or live data
Measure voltage at relay socket: control (coil) terminal, coil ground, and switched output
Check for aftermarket accessories tied into power circuits that may interfere

Signal parameters

Battery voltage at relay supply terminal: ~12.4–12.8 V (engine off) and ~13.5–14.8 V (engine running)
Control (coil) apply voltage when module commands relay: ~11–14 V
Coil resistance (typical 12 V automotive relay): ~50–200 ohms (manufacturer-specific — consult service data)
Switched output voltage when relay closed: within 0.5 V of battery voltage
Control signal idle when relay off: ~0 V (or open) depending on driver type
Coil current draw when energized: usually

Diagnostic algorithm

Record stored codes and freeze-frame data with a scan tool. Attempt to actuate the relay from the scan tool/actuator test if available and observe behavior.
Visually inspect related fuses, the relay, relay socket and harness for corrosion, melted insulation, or loose terminals. Replace blown fuses as required.
With ignition off, remove the relay and inspect socket pins for corrosion or damage. Measure coil resistance across the two coil terminals on the relay (compare to spec).
Backprobe the relay socket: measure battery supply at the common terminal, control voltage at the coil input while commanding the relay, and ground at the coil ground terminal. Do NOT short pins together.
If control voltage is present but relay does not click or switched output is absent, substitute a known-good relay and re-test.
If relay still does not operate and control voltage is absent, trace the control circuit back to the BCM/ECU: check continuity to the module, check grounds, and inspect for shorts to B+ or ground.
If wiring and relay are good but the control module does not provide proper drive, test the module outputs per manufacturer procedures. Consider ECU/BCM replacement only after confirming wiring and relay integrity.
After repairs, clear codes, perform actuator tests, and verify circuits under various operating conditions (key on, engine running). Re-scan for reoccurrence and monitor for intermittent behavior.

Likely causes

Relay coil open or contacts welded/stuck closed
Corroded relay socket or connector pins causing intermittent contact
Broken wire or pin pushed out of connector to relay
Blown inline fuse supplying the relay coil or switched output
Control module output transistor/driver failure
Short to ground on the relay output circuit

Fault status

⚠️ Status

Stored when the system power relay control circuit is detected to be open, shorted, or otherwise not operating within expected parameters, indicating the relay or its control wiring/driver may be faulty.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours