Bobcat A8405 (84-05) Fault Code: ACD/RACD Output “E” Short to Battery
Also shown on the panel as 84-05 · Also called ACD Output ‘E’ Short to Battery, ACD/RACD Output “E” Short to Battery
ACD/RACD Output “E” Short to Battery · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
A8405 (panel code 84-05) sets when the Bobcat ACD/RACD (Attachment Control Device / Remote Attachment Control Device) controller sees voltage on Output "E" (controller pin J1 B-26) when that output has not been commanded on. When this happens, the controller disables Output "E" until the fault clears and power is cycled.
Medium severity. Output "E" is disabled the moment the code sets, so whatever attachment function runs on that output stops working. It is not an engine-damage or immediate safety-shutdown event by itself, but running an attachment with a disabled output can affect control of implements, so it should be diagnosed before continuing normal work.
What does Bobcat error code A8405 mean?
A8405 is an electrical fault on the attachment control side of Bobcat loader and excavator platforms. The ACD/RACD controller manages power outputs, labeled with letters like "E", that feed solenoids on attachments. Each output is switched on only when the controller commands it. If the controller senses voltage present on Output "E" at pin J1 B-26 while it has not told that circuit to turn on, it flags A8405 and shuts that output down as a protective measure.
This matters because a short to battery voltage on an output circuit means that circuit can no longer be controlled normally. Instead of the controller deciding when the attachment function tied to Output "E" turns on, stray battery voltage is already present on the wire, which can make the function stick on, behave unpredictably, or simply stop working once the controller disables it for protection.
The fault is tied to the wiring and solenoid for Output "E" specifically, plus the return (ground) side of that same circuit, so a proper diagnosis has to check both the supply side and the return side of the circuit, not just the output wire alone.
Common causes of A8405
- Output "E" wire at controller pin J1 B-26 shorted to battery voltage
- Return wire, controller pin J1 A-26, shorted to battery voltage
- Failed or shorted Output "E" solenoid
- Internal fault in the ACD/RACD controller
- Moisture, corrosion, or pushed-back pins in the ACD/RACD controller connectors, mainframe harness, attachment control harness, or the Output "E" solenoid connector
- Intermittent condition (loose connections, corrosion, pushed-back pins, controller, or harness, alone or in combination) that may not be reproducible if the fault is not active at the time of testing
How to troubleshoot Bobcat A8405: first checks
- Confirm the key switch is on / in run-enter and check whether the code is currently active or stored, since an intermittent fault may not be present at the time of testing
- Inspect the ACD/RACD controller connectors, mainframe harness connectors, and attachment control harness connectors for moisture, corrosion, or pushed-back pins
- Check the Output "E" solenoid and its connector for damage, corrosion, or a shorted internal coil
- With the system safely de-energized, check for a short to battery voltage on the Output "E" wire at controller pin J1 B-26
- Check the return wire at controller pin J1 A-26 for a short to battery voltage as well, since a shorted return can trigger the same code
- If wiring and the solenoid check out clean, suspect the ACD/RACD controller itself as the source of the fault
How the code clears
Once the wiring, solenoid, or controller repair is complete, cycle power (turn the key switch off and back on) to clear the code. No separate reset procedure is listed for this code.
Affected models and serial ranges
A8405 appears in our records across 20 Bobcat models. Match your machine by model and serial number.
| Model | Serial ranges |
|---|---|
| E35 | SN A93K110001-99999, SN AC2P11001-99999 |
| E42 | SN AG3411001-99999 |
| E45 | SN AG3G11001-99999, SN AHHC11001-99999 |
| E55 | SN ARWM11001-99999, SN ASW311001-99999 |
| S510 | SN A3NJ11001-99999, SN A3NK11001-99999, SN ATZC11001-99999 |
| S530 | SN A7TV11001-99999, SN ATZD11001-99999 |
| S550 | SN A3NK11001-A3NL99999, SN A3NM11001-99999 |
| S570 | SN A7U711001-799999, SN A7U811001-899999 |
| S590 | SN ANMN11001-99999, SN ANMP11001-99999 |
| S630 | SN A3NT10001-12369, SN A3NT12370-99999, SN A3NU11001-11111, SN A3NU11112-99999 |
| S650 | SN A3NV11001-13098, SN A3NV13099-99999, SN A3NW11001-11248, SN A3NW11249-99999 |
| S750 | SN A3P211001-299999 |
| S770 | SN A39511001-99999, SN A3P411001-99999 |
| T550 | SN A7UJ11001-AJZV12276 |
| T590 | SN ALJU11001-999999, SN B37811001-999999, SN B3Z711001-999999 |
| T630 | SN A7PU11001-11663, SN A7PU11664-99999 |
| T650 | SN A3P012214-099999, SN A3P111242-199999 |
| T750 | SN ANKA11001-A99999 |
| T770 | SN A3P811001-899999, SN A3P911001-999999 |
| T870 | SN A3PG11001-99999 |
Frequently asked questions
What does Bobcat code A8405 mean?
It means the ACD/RACD (Attachment Control Device / Remote Attachment Control Device) controller detected voltage on Output "E", at controller pin J1 B-26, when it had not commanded that output on. The controller responds by disabling Output "E".
What is the panel display form of A8405?
On the display it shows as 84-05.
Will A8405 stop my machine from running?
The code itself disables Output "E" only, affecting whatever attachment function is wired to that output. It does not by itself describe an engine shutdown, but any function tied to Output "E" will stop working correctly until the fault is fixed.
Which Bobcat machines can show code A8405?
It applies across a range of Bobcat loaders and excavators, including E35, E42, E45, E55, S510, S530, S550, S570, S590, S630, S650, S750, S770, T550, T590, T630, T650, T750, and T770/T870 models equipped with ACD/RACD attachment control.
How do I clear A8405 after repair?
Cycle power to the machine, turning the key switch off and back on, once the repair is complete. No other clearing procedure is documented for this code.
Why does A8405 mention both an output wire and a return wire?
Because a short to battery voltage on either the Output "E" wire (pin J1 B-26) or its return wire (pin J1 A-26) can cause the controller to see unexpected voltage on that circuit and set the same code, so both need to be checked.
The code only shows up sometimes. What should I do?
Intermittent A8405 codes are commonly caused by loose connections, corrosion, or pushed-back pins in the connectors, and may not be reproducible if the circuit is not shorted at the moment of testing. A careful visual and physical inspection of the connectors and harness is the best starting point even if the fault is not active.