Bobcat M4621 (46-21) Fault Code: 5 Volt Sensor Supply Out of Range High
Also shown on the panel as 46-21
5 Volt Sensor Supply Out of Range High · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
M4621 (panel code 46-21) sets when the gateway controller sees more than 5.5 volts on the 5 volt sensor supply wire (5100 or 3930 depending on model/harness) with the key switch in run/enter. This supply feeds the seatbar sensor and the engine oil pressure sensor, so this fault can drag other codes along with it.
Medium severity. M4621 itself is a sensor supply voltage fault, not an immediate engine or hydraulic shutdown code. But because the same 5 volt supply feeds the seatbar sensor and engine oil pressure sensor, a high supply voltage can cause those safety and engine-protection systems to read incorrectly, so it should not be ignored past the current shift.
What does Bobcat error code M4621 mean?
M4621 means the gateway controller has measured more than 5.5 volts on the 5 volt sensor supply circuit, which should normally sit at 5 volts. This supply wire (labeled 5100 on some machines, 3930 on others) powers the seatbar sensor and the engine oil pressure sensor.
Because both of those sensors depend on this same supply, an out-of-range-high condition on the supply line can make the controller misread seatbar position or engine oil pressure, which is why M4621 often shows up alongside code M1121 (seatbar sensor out of range high), M0613 (engine speed no signal), or M0421 (engine oil pressure out of range high).
This is fundamentally a wiring and controller diagnostic, not a mechanical failure of the seatbar or oil pressure sensor themselves. The fix is almost always in the supply circuit or the connectors that carry it.
Common causes of M4621
- 5 volt supply wire (5100 or 3930, depending on the machine) shorted to a source of higher supply voltage.
- Fault in the gateway controller itself.
- Moisture, corrosion, or pushed-back pins in the gateway controller connectors, mainframe harness, or cab harness.
- Intermittent condition: if the code is not active at the time of testing, the root cause may not be found right away. Probable contributors in this case include loose connections, corrosion, pushed-back pins, the controller, the wire harness, or a combination of these.
How to troubleshoot Bobcat M4621: first checks
- Turn the key switch to run/enter and check for the active M4621 code, along with any related codes such as M1121, M0613, or M0421 that may be present at the same time.
- Inspect the gateway controller connectors, mainframe harness connectors, and cab harness connectors for moisture, corrosion, or pins that have pushed back out of their sockets.
- Trace the 5 volt sensor supply wire (5100 or 3930, depending on model) for chafing or contact with a higher-voltage circuit that could be shorting it to supply voltage.
- Check the seatbar sensor and engine oil pressure sensor circuits for shared symptoms, since a bad supply reading here can be the reason those systems are also throwing codes.
- If the code does not stay active during testing, treat it as intermittent and focus inspection on connector condition and harness routing rather than assuming a component is bad.
How the code clears
This code is self resetting. Once the voltage on the 5 volt sensor supply returns to a normal range, no separate clearing step is listed beyond correcting the underlying wiring, connector, or controller fault.
Affected models and serial ranges
M4621 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 M4621 mean?
It means the gateway controller detected more than 5.5 volts on the 5 volt sensor supply circuit that feeds the seatbar sensor and the engine oil pressure sensor. Normal supply voltage should be 5 volts, so this is an out-of-range-high fault.
Is M4621 the same as the 46-21 code on the dash panel?
Yes. 46-21 is simply the numeric panel display form of M4621 on Bobcat machines that show codes in that format.
Why do I also see M1121, M0613, or M0421 with M4621?
All three of those sensors or readings depend on the same 5 volt sensor supply. If that supply voltage goes out of range high, the seatbar sensor (M1121), engine speed signal (M0613), or engine oil pressure sensor (M0421) can also report faults at the same time.
What wire number should I check for M4621?
Check wire 5100 on machines that use that numbering, or wire 3930 on machines that use that harness designation. Both are the 5 volt sensor supply circuit, just different wire labels depending on the model and harness.
Will M4621 clear itself after I fix the wiring?
Yes, this code is self resetting. Once the short or connector problem causing the over-voltage condition is corrected, the code clears on its own without a manual reset procedure.
Can a bad gateway controller cause M4621 instead of a wiring problem?
Yes. The gateway controller itself is listed as a possible cause, along with a wire shorted to supply voltage or corrosion and pushed-back pins in the connectors. Rule out the harness and connectors first since those are more common and cheaper to fix.
What if the M4621 code isn't active when I test the machine?
If the code is intermittent and not present at the time of testing, the root cause may not be identifiable right away. Focus on inspecting connections, corrosion, and pushed-back pins in the gateway controller, mainframe harness, and cab harness, since those are the most likely intermittent culprits.