What Does B1305 Mean?
This code indicates the Body Control Module (BCM) detected an abnormal short circuit to ground in the accessory delay relay coil circuit. The accessory delay relay controls power distribution to accessories after the ignition is turned off, allowing features like power windows, radio, and interior lights to function for a predetermined time. The BCM has identified that the relay coil circuit is drawing excessive current or has an unintended path to ground, preventing proper relay operation.
Common Causes
40%
Damaged wiring harness with chafed insulation causing wire-to-ground short between BCM and relay
30%
Failed accessory delay relay with internal short circuit in coil windings
20%
Corroded or damaged relay socket/connector with moisture intrusion causing ground short
10%
Faulty Body Control Module with shorted internal relay driver circuit
Diagnostic Steps
1
Step 1: Perform visual inspection of the accessory delay relay, relay socket, and associated wiring harness for obvious damage, corrosion, melted terminals, or chafed wires rubbing against metal body panels or sharp edges
2
Step 2: Remove the accessory delay relay and measure resistance across the relay coil terminals using a digital multimeter (typical reading 70-120 ohms). Also test for continuity between each coil terminal and relay case (should read infinite resistance/open circuit)
3
Step 3: With relay removed and ignition off, disconnect BCM connector and measure resistance between the relay coil control wire terminal (at relay socket) and known good chassis ground using multimeter. Reading should be infinite resistance; any measurable continuity indicates wiring short to ground
4
Step 4: Inspect wiring harness routing from BCM to relay socket, checking for pinched wires at firewall grommets, door hinges, or mounting brackets. Use resistance measurements at multiple points along the harness to isolate short location
5
Step 5: If wiring tests good, reconnect BCM and install a new known-good relay. Clear codes and operate accessories with ignition off to verify relay engagement. Monitor for code return which would indicate BCM internal driver circuit failure
6
Step 6: After repair, cycle ignition on/off several times and operate all accessory delay functions (windows, sunroof, radio) to confirm proper operation and verify code does not return
Estimated Repair Cost
$100 - $650
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) detected an abnormal short circuit to ground in the accessory delay relay coil circuit. The accessory delay relay controls power distribution to accessories after the ignition is turned off, allowing features like power windows, radio, and interior l...
The most common cause of B1305 (Accessory Delay Relay Coil Circuit Short To Ground) is: Damaged wiring harness with chafed insulation causing wire-to-ground short between BCM and relay
Typical repair costs for B1305 range from $100 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle is safe to drive as this affects convenience features only, not critical safety systems. However, some accessories may not function properly after key-off, and the short circuit could potentially drain the battery or cause electrical damage if left unrepaired for extended periods.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1305 to identify the root cause.
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Quick Info
Category
Body
System
Body Electrical System
Difficulty
Type
Manufacturer
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