Bobcat A8403 (84-03) Fault Code: ACD/RACD Output "E" Error Off
Also shown on the panel as 84-03 · Also called ACD Output ‘E’ Error Off
ACD/RACD Output "E" Error Off · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
A8403 (panel display 84-03) sets when the ACD/RACD controller sends voltage to energize the attachment solenoid coil on output "E" (wire 5100) but detects no voltage return, or the controller senses a large current draw and shuts the output off. The right instrument panel ACD/RACD icon will blink and the attachment on output "E" will stop working.
Medium severity. The affected attachment output will not function until the fault is corrected, which can stop attachment work, but it does not by itself indicate a driving or engine safety hazard. Treat it as a stop-and-diagnose item before relying on that attachment.
What does Bobcat error code A8403 mean?
A8403 is set by the Advanced Combination Deflector or Remote Advanced Combination Deflector (ACD/RACD) controller, which manages attachment control outputs on many Bobcat skid-steer and compact track loader models. Output "E", carried on wire 5100, is used to energize an attachment solenoid coil.
When the controller commands voltage on output "E" to energize that solenoid, it expects to see voltage present on the circuit. If it detects no voltage on wire 5100 despite sending the command, or if it senses an excessive current draw on that circuit, it shuts the output off to protect the wiring and controller, and it will not re-energize that output until the condition is corrected.
The result is a blinking ACD/RACD icon on the right instrument panel and loss of function for whatever attachment feature runs off output "E". This is an electrical fault in the attachment control circuit rather than a hydraulic or engine problem, though it affects attachment operation.
Common causes of A8403
- Shorted solenoid coil on the attachment connected to output "E".
- Circuit output "E" wire 5100 shorted to ground between the controller and the attachment solenoid.
- A fault in the ACD/RACD controller itself.
- Moisture, corrosion, or pushed-back pins in the mainframe or attachment control harness connectors.
- Intermittent causes that may not be present at the time of testing, including loose connections, corrosion, pushed-back pins, the controller, the wire harness, or a combination of these problems.
How to troubleshoot Bobcat A8403: first checks
- With the key switch in run/enter position, check the right instrument panel for the blinking ACD/RACD icon to confirm the code is currently active rather than historical/intermittent.
- Inspect the attachment solenoid coil for the output "E" circuit and test it for an internal short.
- Trace wire 5100 from the ACD/RACD controller to the attachment solenoid connector, checking for chafed insulation or a short to ground anywhere along the run.
- Disconnect and inspect the mainframe and attachment control harness connectors for moisture, corrosion, and pushed-back or bent pins.
- If no fault is found and the code was intermittent, recheck all connections in the circuit since loose connections, corrosion, or pushed-back pins can cause a code that is not present at the time of testing.
- If wiring and solenoid check out, suspect the ACD/RACD controller itself.
How the code clears
Once the repair is complete, cycle the key switch power off and back on to clear the code. No other reset procedure is listed for this code.
Affected models and serial ranges
A8403 appears in our records across 16 Bobcat models. Match your machine by model and serial number.
| Model | Serial ranges |
|---|---|
| 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 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 A8403 mean?
It means the ACD/RACD controller sent voltage to energize an attachment solenoid coil on output "E" (wire 5100) but did not detect voltage on that circuit, or it sensed too much current draw and shut the output off. The attachment run off that output will not work and the right panel ACD/RACD icon will blink.
Can I keep operating the machine with A8403 active?
You can generally continue operating the machine itself, but the attachment feature wired to output "E" will not function until the fault is fixed. Confirm exactly which attachment or function that output controls on your machine before relying on it.
What is the most common cause of A8403?
Bobcat lists a shorted solenoid coil and wire 5100 shorted to ground as leading causes, along with moisture, corrosion, or pushed-back pins in the mainframe or attachment control harness connectors.
How do I clear A8403 after repair?
Cycle the key switch power off and back on. No other clearing procedure is listed for this code.
Why does the code come and go instead of staying on?
Bobcat notes that if the code is intermittent and not active during testing, the cause may not be found right away. Probable intermittent causes include loose connections, corrosion, pushed-back pins, the controller, or the wire harness, or a combination of these.
Which Bobcat machines can show A8403?
It applies to models S510, S530, S550, S570, S590, S630, S650, S750, S770, T550, T590, T630, T650, T750, and T770/T870 equipped with an ACD/RACD attachment control system.
Is A8403 an electrical or hydraulic fault?
It is an electrical fault in the attachment control circuit, specifically the output "E" solenoid drive circuit on wire 5100, not a hydraulic pressure or flow issue.