Bobcat M0509 (05-09) Fault Code: Hydraulic Charge Pressure Low
Also shown on the panel as 05-09 · Also called Hydraulic Charge Pressure Too Low
Hydraulic Charge Pressure Low · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
M0509 (panel display 05-09) sets when the gateway controller sees hydraulic charge pressure below the machine's specified value for 10 seconds on signal wire 3190 or 3420, depending on model wiring. It points to low charge pressure in the hydraulic system, either from low oil, a weak pump, a bad sensor, or wiring problems on the 8.0 volt sensor supply.
High severity. Low hydraulic charge pressure can mean the hydrostatic or hydraulic pump isn't getting adequate supply, which risks pump damage and loss of drive or function performance if run for long. Diagnose before continuing heavy work, though the machine will usually still move and function in a limited way while the code is active.
What does Bobcat error code M0509 mean?
M0509 is Bobcat's code for low hydraulic charge pressure, shown on the panel as 05-09. The gateway controller monitors a hydraulic charge pressure sensor that reports back on a signal wire, either wire 3190 or wire 3420 depending on the machine's wiring variant. When that signal reads below the pressure value calibrated for the machine for 10 seconds with the key on and the engine running, the controller sets M0509.
The hydraulic charge pressure sensor itself runs on an 8.0 volt supply from the gateway controller, delivered on a dedicated supply wire (5190 or 3400 depending on variant). If that supply, the sensor, the signal wire, or the connectors have a problem, the controller can read a false low pressure even when the hydraulic system is fine.
Charge pressure is what keeps the hydrostatic and hydraulic pump circuits properly fed and lubricated. Running with genuinely low charge pressure for any length of time can accelerate pump wear, so this code is worth taking seriously even if the machine still seems to drive and work normally.
What triggers a Bobcat M0509 code?
The gateway controller sets M0509 when it detects hydraulic charge pressure below the specified value for the machine, held for 10 seconds, on the charge pressure sensor's signal wire (3190 or 3420). This is only evaluated with the key switch in run/enter and the engine running.
Common causes of M0509
- Low hydraulic oil level in the reservoir
- Low hydraulic charge pressure caused by a mechanical problem with the pump itself
- A fault on the sensor's 8 volt supply wire (5190 or 3400 depending on model wiring)
- A failed or failing hydraulic charge pressure sensor
- A problem in the gateway controller itself
- Moisture, corrosion, or pushed-back pins in the gateway controller connectors, the hydraulic charge pressure sensor connector, or the mainframe wire harness
- An intermittent fault from loose connections, corrosion, pushed-back pins, the controller, the wire harness, or a combination of these, which may not reproduce a hard fault at the time of testing
How to troubleshoot Bobcat M0509: first checks
- Check the hydraulic oil level and top off if low, then recheck for the code before moving on to other checks
- Inspect the hydraulic charge pressure sensor connector and the gateway controller connectors for moisture, corrosion, or pins that look pushed back out of place
- Trace the mainframe wire harness between the sensor and the gateway controller for chafing, loose connections, or damage
- Verify the sensor's 8.0 volt supply is present and steady at the connector before condemning the sensor itself
- If oil level and wiring check out, suspect a mechanical charge pump problem or a failed sensor and follow the pressure test procedure in the service manual for the specific model
- If the code will not reproduce during testing, treat it as intermittent and focus on loose connections, corrosion, or pushed-back pins as the most likely repeat offenders
How the code clears
M0509 is self resetting. No separate clearing step is listed, so once the actual low charge pressure condition (oil level, pump, sensor, or wiring) is corrected, the code should clear on its own once the controller sees a normal pressure reading.
Affected models and serial ranges
M0509 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-ATZC99999 |
| 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 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, SN A3PH11001-99999 |
Frequently asked questions
What does Bobcat code M0509 mean?
It means the gateway controller detected hydraulic charge pressure below the specified level for the machine, held for 10 seconds. It's shown on some panels as 05-09.
Is it safe to keep working with M0509 active?
It's not advisable. Low charge pressure risks pump wear or damage over time, so it's best to stop and check hydraulic oil level and wiring before continuing heavy use.
What's the most common cause of M0509?
Low hydraulic oil level is the simplest and most common cause listed, but the sensor, its 8 volt supply wire, connector corrosion, and a mechanical pump problem are all listed possible causes too.
Do I need a scan tool to clear M0509?
No. The code is self resetting, meaning once the underlying low pressure condition is fixed, it clears on its own without a manual reset step.
Why does the wire number for M0509 differ between machines?
Some Bobcat models route the charge pressure sensor signal on wire 3190 with an 5190 supply wire, while others use wire 3420 with a 3400 supply wire. Both wiring variants set the same M0509 code under the same logic.
Can a bad connector cause M0509 without an actual hydraulic problem?
Yes. Moisture, corrosion, or pushed-back pins in the gateway controller or sensor connectors can cause a false low pressure reading even if the hydraulic system itself is fine.
What if the code doesn't show up when I test the machine?
That points to an intermittent problem. Likely causes are listed as loose connections, corrosion, pushed-back pins, the controller, the wire harness, or a combination, so it's worth a thorough inspection even without a live fault.