Bobcat A8406 (84-06) Fault Code: ACD/RACD Output “E” Short to Ground
Also shown on the panel as 84-06 · Also called ACD Output ‘E’ Short to Ground, ACD/RACD Output “E” Short to Ground
ACD/RACD Output “E” Short to Ground · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
A8406 (panel form 84-06) sets when the ACD/RACD controller commands output "E" but does not detect voltage on that circuit, controller pin J1 B-26, or its return wire, controller pin J1 A-26. When the code sets, output "E" is disabled until the fault is cleared and power is cycled.
Medium severity. Output "E" is disabled while the code is active, so whatever attachment function relies on that output will not work. This is not an engine-damage or immediate safety-critical fault by itself, but a lost attachment output can affect control of an attachment, so treat it as a stop-and-diagnose item before relying on that function.
What does Bobcat error code A8406 mean?
A8406 is set by the Advanced Control Display or Rapid Attachment Control Display (ACD/RACD) controller, the module that manages Bobcat attachment control outputs. Output "E" is one of the controller's commanded outputs, wired through controller pin J1 B-26 with its return path on controller pin J1 A-26.
When the controller sends a command to output "E", it expects to see a certain voltage response on that circuit. If it does not detect that voltage, it concludes the circuit is shorted to ground or otherwise faulted, sets code A8406, and disables output "E" as a protective measure. This means whatever attachment function is wired to output "E" will stop responding until the fault is found and cleared.
This code applies across a wide range of Bobcat compact excavators, skid-steer loaders, and compact track loaders that use the ACD/RACD attachment control system, including the E35, E42, E45, E55, S510, S530, S550, S570, S590, S630, S650, S750, S770, T550, T590, T630, T650, T750, T770, and T870 models.
What triggers a Bobcat A8406 code?
The code sets whenever the key switch or run/enter switch is on and the controller commands output "E" but does not detect voltage on controller pin J1 B-26 or the return wire on controller pin J1 A-26.
Common causes of A8406
- Output "E" wire (controller pin J1 B-26) or its return wire (controller pin J1 A-26) shorted to ground.
- A fault in the output "E" solenoid itself.
- A fault in the ACD/RACD controller.
- Moisture, corrosion, or pushed back pins in the ACD/RACD controller connectors, the mainframe harness, the attachment control harness, or the output "E" solenoid connector.
- Intermittent conditions such as loose connections, corrosion, pushed back pins, a controller fault, or a wire harness fault, or a combination of these, especially if the code is not active at the time of testing.
How to troubleshoot Bobcat A8406: first checks
- With key switch / run-enter on, check for the code and note whether it is currently active or was only stored as historical.
- Inspect the ACD/RACD controller connectors, mainframe harness connectors, and attachment control harness connectors for moisture, corrosion, or pushed back pins, paying close attention to J1 B-26 and J1 A-26.
- Inspect the output "E" solenoid and its connector for corrosion, damage, or a shorted winding.
- Trace the output "E" circuit (pin J1 B-26) and its return wire (pin J1 A-26) for chafed insulation or contact with ground, especially at harness routing points and connector backshells.
- If the code is intermittent and not active during testing, recheck all connectors and harness sections along the output "E" circuit since the fault may not be present at the time of the inspection.
- If wiring, connectors, and the solenoid all check out, suspect the ACD/RACD controller itself.
How the code clears
Once the repair is complete, the documented clearing step is to cycle power (turn the key switch off, then back on). No separate reset procedure is listed for this code beyond cycling power.
Affected models and serial ranges
A8406 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 A8406 mean?
It means the ACD/RACD controller commanded output "E" but did not detect the expected voltage on that circuit (controller pin J1 B-26) or its return wire (controller pin J1 A-26), so the controller judged the circuit shorted to ground and disabled output "E".
What is the panel display form of this code?
On the panel it displays as 84-06, which corresponds to A8406 in Bobcat's fault code list.
Will my attachment still work with code A8406 active?
The function tied to output "E" will not work because the controller disables that output when the code is active. Other attachment functions not wired to output "E" should be unaffected.
What Bobcat machines can show code A8406?
It can appear on E35, E42, E45, E55, S510, S530, S550, S570, S590, S630, S650, S750, S770, T550, T590, T630, T650, T750, and T770 machines equipped with the ACD/RACD attachment control system.
How do I clear code A8406 after repair?
Cycle the key switch off and back on. That is the only clearing step listed for this code.
Why does my code A8406 come and go?
An intermittent A8406 usually points to a loose connection, corrosion, or a pushed back pin somewhere in the output "E" circuit rather than a constant dead short. If the code is not active when you test, check all the connectors and harness sections along that circuit anyway, since the fault may not show up at that moment.
Is A8406 a safety-critical fault?
It is not described as an engine or hydraulic damage risk, but losing control of an attachment function unexpectedly can create a safety concern depending on what output "E" controls on your machine. Diagnose it before continuing to rely on that attachment function.