B1305

Code

Other B — Body

Accessory Delay Relay Coil Circuit Short To Ground

Brand: Other

Type: B — Body

Views: UK: 30 EN: 47 RU: 50

AI status

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Page language: EN

Causes

Damaged wiring harness with insulation rubbed through to chassis ground
Corroded or damaged relay connector pins
Faulty accessory delay relay (internal short in coil)
Aftermarket accessory or modification incorrectly tied into the relay circuit
Grounding point corrosion or a loose ground wire
Body control module (BCM) or relay driver output damaged

Symptoms

Accessory delay (continued power after key-off) inoperative or behaves erratically
Accessories (radio, windows, etc.) may turn off immediately or stay on
Blown fuse(s) on accessory or relay circuit
Possible parasitic battery drain when ignition is off
DTC B1305 present and may reappear after repairs

What to check

Retrieve DTC(s) and freeze frame data with scan tool; note battery voltage at time of fault
Visually inspect relay, connector, wiring harness and ground points for damage or corrosion
Check related fuses for open/blown condition
Remove accessory delay relay and inspect for internal damage or oil/blackening
Measure coil resistance across relay coil terminals with relay removed
With relay removed, check continuity from the relay coil control circuit to chassis ground

Signal parameters

Relay control voltage when energized: approx. battery voltage (typically 11–14 V) at relay control terminal when BCM commands relay
Coil resistance (typical): generally in the range of ~30–200 ohms for common automotive relays (vehicle-specific values vary)
Coil current when energized: typically tens to a few hundred mA (depends on coil resistance)
Expected with relay removed: open circuit (no continuity) between the control feed and chassis ground (infinite or very high resistance)

Diagnostic algorithm

Verify code and record conditions: use scan tool to confirm B1305 and note ignition state and battery voltage.
Perform a visual inspection: check relay, connector, wiring harness routing, grommets and nearby components for abrasion or corrosion.
Check fuses: inspect and replace any blown fuses; if a fuse repeatedly blows, suspect a short to ground.
Remove the accessory delay relay: inspect for signs of overheating or internal short. If available, swap with an identical known-good relay and see if code clears.
Measure coil resistance: with relay removed, measure ohms across coil terminals. Compare to specification if available. Very low resistance or near short indicates a bad relay.
Check for short to ground on control circuit: with relay removed, measure resistance between the control/coil feed pin and chassis ground. A near-zero reading indicates a short in the wiring or connector.
Isolate wiring: disconnect connectors along the harness (including any intermediate splice or connector blocks) and re-test to locate the shorted section.
Inspect/repair grounding points: clean and tighten any ground connections associated with the circuit.
If wiring and relay check OK, test BCM/relay driver: use an appropriate scope or test light methods per service manual; replace BCM only after wiring and relay have been verified faulty.
Clear codes and road-test/operate accessories to confirm repair; monitor for code reappearance and check battery voltage for abnormal drain.

Likely causes

Chafed wire contacting body or frame on coil feed or control conductor
Relay coil internally shorted to its metal casing or terminal
Corroded connector allowing low-resistance path to ground
Previous poor repair or splice that created a short to ground

Fault status

⚠️ Status

Accessory Delay Relay Coil Circuit Short To Ground — control circuit has unintended continuity to chassis ground; relay may not operate and fuses may blow.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours