Bobcat D7594 (75-94) Fault Code: Unresponsive Left Speed Sensor
Also shown on the panel as 75-94 · Also called Drive Unresponsive Left Speed Sensor
Unresponsive Left Speed Sensor · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
D7594 (panel code 75-94) sets when the drive/drive plus controller sees a joystick command for movement, the left swash plate sensor reads correctly, but no speed signal comes from the left speed sensor for 18 seconds. It points to a wiring, sensor, or controller problem on the left drive circuit.
High severity. This code affects the machine's ability to detect and control left-side drive speed. Continuing to operate with unresponsive speed feedback risks unpredictable machine movement, especially on slopes or near people. Diagnose before returning to normal work.
What does Bobcat error code D7594 mean?
A code D7594 occurs when the drive/drive plus controller detects a command from the joystick for machine movement, confirms the left swash plate sensor is in the correct position, but receives no speed signal from the left speed sensor for 18 seconds. The controller uses this speed feedback to know how fast, and whether, the machine is actually moving on the left side.
On wheeled machines, the speed sensor sits in the motor carrier and reads magnets on a rotating disk. On track machines, the sensor sits in the drive motor and reads teeth on a metal sprocket. Either way, if the controller commands movement but gets no confirming speed pulse from the left side, it sets D7594 and treats the left drive as unresponsive.
This is a drive-train safety and control code. Left and right drive speed sensing keeps the machine tracking straight and predictable. Losing that feedback on one side can cause pulling, uneven speed, or a machine that does not respond the way the operator expects.
Common causes of D7594
- Open supply wire, ground wire, or signal wire between the left speed sensor and the drive/drive plus controller (wire numbers vary by model/harness: 1540, 5880, 2580, 2880, 3020, 3880, 3080, or 3885).
- Metal particles built up on the speed sensor tip or on the magnetic disc/sprocket it reads, blocking a clean signal.
- A worn, damaged, or failed wheel/track speed sensor, or damage to the magnetic disc or sprocket it detects.
- A fault inside the drive/drive plus controller itself.
- Moisture, corrosion, or pushed-back pins in the drive/drive plus controller connector, the speed sensor connector, or any wire harness connector in that circuit.
- An intermittent condition: if the code is not active at the time of testing, the root cause may not show up immediately. Likely culprits are still loose connections, corrosion, pushed-back pins, the controller, the harness, or a combination of these.
How to troubleshoot Bobcat D7594: first checks
- Confirm the conditions that allow this code to set are present: key switch/run-enter on, Press To Operate Loader (PTOL) enabled, engine running, and an active drive command from the joystick. If any of these are missing, the code logic will not apply.
- Inspect the left speed sensor connector and the drive/drive plus controller connector for moisture, corrosion, or pins that look pushed back out of their sockets.
- Visually inspect the speed sensor tip and the magnetic disc (wheeled machines) or sprocket teeth (track machines) for metal shavings, debris, or physical damage that could block the sensor from reading.
- Check the supply, ground, and signal wires for the left speed sensor circuit for continuity, looking for opens along the harness between the sensor and the controller.
- If the code is not currently active, treat it as possibly intermittent. Wiggle-test connectors and harness runs while watching for the code to reappear, since loose connections and corrosion are common intermittent causes.
- Inspect the drive/drive plus controller itself if wiring, sensor, and connector checks come back clean, since the controller is listed as a possible cause.
How the code clears
Cycle power to clear the code once the repair is complete. No separate clearing step is listed beyond a power cycle.
Affected models and serial ranges
D7594 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 D7594 mean?
It means the drive/drive plus controller commanded left-side machine movement, confirmed the left swash plate sensor was in the correct position, but got no speed signal from the left speed sensor for 18 seconds. The controller flags this as an unresponsive left speed sensor.
Is it safe to keep driving with D7594 active?
It is not recommended. Losing left-side speed feedback can cause uneven or unpredictable drive response. Stop and diagnose the issue before continuing normal operation, especially in tight spaces or on slopes.
What is the panel display code for D7594?
On the display panel, this code shows as 75-94.
What usually causes this code on wheeled versus tracked Bobcat machines?
On wheeled machines, the speed 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. Debris, damage, or wiring faults affecting either type can trigger D7594.
How do I clear D7594 after making a repair?
Cycle the key power off and back on. No additional clearing procedure is listed for this code.
Why does D7594 come and go instead of staying on?
If the code is intermittent, the root cause may not be present during testing. Likely culprits include loose connections, corrosion, pushed-back connector pins, a marginal controller, or harness damage, sometimes a combination of these.
Which Bobcat models can show code D7594?
This code applies to Bobcat S510, S530, S550, S570, S590, S630, S650, S750, S770, T550, T590, T630, T650, T750, and T770 models.