Bobcat D7539 (75-39) Fault Code: Left Swash Plate Sensor Out of Range High
Also shown on the panel as 75-39 · Also called Drive Left Swash Plate Sensor Out of Range High, Left Swash Plate Sensor Out Of Range High
Left Swash Plate Sensor Out of Range High · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
D7539 (panel code 75-39) sets when the drive/drive plus controller sees the left swash plate sensor signal above 4.85 volts, outside the normal 1.0 - 4.0 volt output range. The machine keeps running in speed management mode, but the fault should be diagnosed before returning to full duty.
Medium severity. The machine continues to operate in speed management mode when this code is active, so it is not an immediate shutdown fault. However, running with a faulty swash plate sensor circuit reduces accurate drive control, so it should be diagnosed and repaired before returning to normal operation.
What does Bobcat error code D7539 mean?
D7539 is set on Bobcat loaders and compact track loaders (models S510 through T870, per Bobcat's list) when the drive or drive plus controller detects that the left swash plate sensor signal has climbed above 4.85 volts. The swash plate sensor is mounted at the bottom of the drive pump and is keyed to the internal swash plate, so it reports the position of that plate back to the controller.
Under normal operation, the sensor's output signal should stay within a 1.0 to 4.0 volt range. The sensor itself gets battery voltage supplied from the gateway controller. When the signal reads above the 4.85 volt threshold, the controller flags it as out of range high and logs D7539.
When this code is active, the machine does not shut down. It continues to operate in speed management mode, which is a reduced or altered control mode used while the controller cannot trust the swash plate feedback for normal drive control logic.
A related code, D7540 (left swash plate sensor out of range low), can also appear if there's an intermittent short to supply voltage on the signal wire, for example from a wire that has rubbed through or a pin that has pushed back in its connector.
What triggers a Bobcat D7539 code?
The controller sets D7539 when the left swash plate sensor signal reads above 4.85 volts, compared against the sensor's normal output range of 1.0 to 4.0 volts. This check is active whenever the key switch (run/enter) is on.
Common causes of D7539
- Ground wire 2860 open (this ground wire number applies across the documented variants of this code)
- Signal wire open or shorted to supply voltage: identified as wire 3860 in some machine variants and wire 4950 in others
- Faulty left swash plate sensor itself
- Faulty drive/drive plus controller
- Moisture, corrosion, or pushed-back pins in the drive/drive plus controller connectors, at the swash plate sensor connector, or in the AWS/SJC wire harness
- Intermittent fault: if the code is not active at the time of testing, the cause may not be found immediately. Probable causes in this case still include loose connections, corrosion, pushed-back pins, the controller, the wire harness, or a combination of these
How to troubleshoot Bobcat D7539: first checks
- Confirm the code is active with the key switch in run/enter, and note whether it's currently present or stored as intermittent
- Inspect the signal wire (3860 or 4950 depending on the machine/harness variant) for chafing, rubbed-through insulation, or exposed wire that could short to supply voltage
- Check ground wire 2860 for continuity and confirm it isn't open
- Pull apart and inspect the drive/drive plus controller connectors and the left swash plate sensor connector for moisture, corrosion, or pins that have pushed back out of their sockets
- Inspect the AWS/SJC wire harness along its run for damage, chafe points, or connector issues
- If nothing is found and the code is intermittent, recheck all connections and the harness carefully since the cause may not surface on a single test pass
- Watch for a paired D7540 code (out of range low), which can point to the same signal wire intermittently shorting to supply voltage
How the code clears
Cycle power after completing the repair. No separate clearing step is listed beyond that.
Affected models and serial ranges
D7539 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 |
| 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, SN A3PH11001-99999 |
Frequently asked questions
What does Bobcat code D7539 mean?
It means the drive/drive plus controller has detected the left swash plate sensor signal reading above 4.85 volts, which is outside the sensor's normal 1.0 to 4.0 volt output range. This triggers the out-of-range-high fault.
Can I keep driving the machine with D7539 active?
The machine will continue to run in speed management mode with this code active, so it isn't a hard shutdown. Still, drive control accuracy may be affected, so it's best to diagnose the sensor circuit as soon as practical.
What is the left swash plate sensor and where is it located?
It's a sensor mounted at the bottom of the drive pump, keyed to the swash plate inside the pump, so it reports swash plate position to the drive/drive plus controller. It receives its supply voltage from the gateway controller.
Is wire 3860 or wire 4950 the correct signal wire for my machine?
Both numbers appear in Bobcat's documentation for this code depending on the specific machine and harness variant. Check your machine's wiring diagram to confirm which signal wire number applies.
Why does D7540 sometimes show up along with D7539?
D7540 (left swash plate sensor out of range low) can occur if there's an intermittent short to supply voltage on the signal wire, such as a rubbed-through wire or a pushed-back connector pin. The two codes can be related to the same underlying wiring fault.
How do I clear D7539 after repair?
Cycle the key switch power after finishing the repair. No additional reset procedure is listed for this code.
What if the code doesn't show up when I test the machine?
If D7539 is intermittent and not active during testing, the root cause may not be identifiable right away. Bobcat notes the likely culprits are still loose connections, corrosion, pushed-back pins, the controller, or the wire harness, so a careful inspection of all of these is worthwhile even without an active fault.