Bobcat D7578 (75-78) Fault Code: Right Speed Sensor Out of Range High
Also shown on the panel as 75-78 · Also called Drive Right Speed Sensor Out of Range High, Right Speed Sensor Out Of Range High
Right Speed Sensor Out of Range High · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
Bobcat code D7578 (panel display 75-78) means the drive controller sees pulses from the right speed sensor above 4.85 volts, which is out of range. When this happens the machine drops into speed management mode until the fault is fixed.
Medium severity. D7578 does not shut the machine down, but it forces speed management mode, which limits how the drive system responds. It should be diagnosed the same shift it appears, especially before the machine is used for travel-heavy work.
What does Bobcat error code D7578 mean?
Bobcat's drive controller uses the right speed sensor to figure out how fast and whether the machine is moving. On wheeled machines like the S510 through S770 skid steers, this sensor sits in the motor carrier and reads magnets on a rotating disk. On track machines like the T550 through T870, the sensor sits in the drive motor and reads teeth on a metal sprocket.
Code D7578 sets when the controller detects that the signal pulses from the right speed sensor are greater than 4.85 volts, which is outside the normal working range for that signal. Since the controller can no longer trust the right side speed data, it puts the machine into speed management mode as a protective measure until the issue is resolved.
Common causes of D7578
- Signal wire (labeled 3000 or 3870, or 3070 or 3875 depending on model) shorted to supply voltage
- 5 volt supply wire (labeled 1530 or 5870 depending on model) shorted to supply voltage
- Ground wire (labeled 2570 or 2870 depending on model) open
- Faulty right speed sensor
- Faulty drive controller
- Moisture, corrosion, or pushed-back pins in the drive controller connectors or SJC harness connectors
- Intermittent fault: if the code is not active at the time of testing, the cause may not be found right away. Possible contributors include loose connections, corrosion, pushed-back pins, the controller, the wire harness, or a combination of these
How to troubleshoot Bobcat D7578: first checks
- Turn the key switch to run/enter (the code only sets under this condition) and confirm whether D7578 is currently active or was logged historically.
- Inspect the drive controller connectors and SJC harness connectors for moisture, corrosion, or pins that have been pushed back out of their sockets.
- Check the right speed sensor wiring for the signal wire, 5 volt supply wire, and ground wire specific to your model (wire numbers vary by machine, see causes list) for shorts to supply voltage or an open ground.
- Visually inspect the right speed sensor itself, along with the rotating disk with magnets (wheel machines) or the sprocket teeth (track machines), for damage, debris, or excessive gap.
- If the code is intermittent and not active during testing, focus on wiggle-testing connectors and checking for loose or corroded terminals rather than assuming a single failed part.
How the code clears
D7578 is self resetting. Once the underlying wiring, sensor, or controller issue is repaired, the code clears on its own without a separate manual reset procedure.
Affected models and serial ranges
D7578 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 D7578 mean?
It means the drive controller detected that the right speed sensor's signal pulses were above 4.85 volts, which is out of the expected range. The controller responds by putting the machine into speed management mode.
Can I keep operating the machine with D7578 active?
The machine will still run, but it operates in speed management mode, which limits normal drive response. It is best to diagnose and repair the fault before relying on the machine for regular work.
Do I need a scan tool to clear D7578?
No separate reset procedure is listed for this code. It is self resetting once the wiring, sensor, or controller problem causing it has been repaired.
Which Bobcat models can show code D7578?
This code applies to a range of skid steer and track loader models including the S510, S530, S550, S570, S590, S630, S650, S750, S770, T550, T590, T630, T650, T750, T770, and T870.
Is the right speed sensor different on wheeled versus track machines?
Yes. On wheeled machines the sensor is in the motor carrier and reads magnets on a rotating disk. On track machines the sensor is in the drive motor and reads teeth on a metal sprocket.
Why do the wire numbers for D7578 vary between machines?
Bobcat uses different wire numbering on different models and harness variants. The signal wire may be labeled 3000, 3070, 3870, or 3875, the 5 volt supply wire may be 1530 or 5870, and the ground wire may be 2570 or 2870 depending on the specific machine.
What if the code shows up but is not active when I test the machine?
Intermittent D7578 faults can be hard to pin down. Likely causes include loose connections, corrosion, pushed-back pins, a wiring harness issue, or the controller itself, so a careful inspection of connectors and harness routing is the best starting point.