Bobcat M4902 (49-02) Fault Code: Rear Light Relay Error On
Also shown on the panel as 49-02
Rear Light Relay Error On · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
M4902 (panel code 49-02) sets when the gateway controller sees voltage on the rear light feedback wire (3440 or 6230 depending on model) when the rear lights are not commanded on. It's an electrical fault tied to the rear work light circuit, not a lighting failure the operator will necessarily notice right away.
Low severity. This is an electrical feedback fault, not a safety-critical system failure. The rear lights themselves may still work, but the fault should be diagnosed before it masks a wiring short that could cause other electrical issues down the line.
What does Bobcat error code M4902 mean?
M4902 is a Bobcat gateway controller fault that fires when the controller reads voltage on the rear light feedback circuit at a time when it did not send a command to turn the rear lights on. In other words, the controller expects the feedback wire to be at a certain state and it isn't, which points to unexpected voltage getting onto that wire.
Depending on the machine and harness revision, the feedback wire involved is labeled either 3440 or 6230, both tied back to wire 6200 in the rear light circuit. The gateway controller monitors this line to confirm the rear work lights relay is only energized when actually commanded.
This code covers skid steers and compact track loaders including the S510, S530, S550, S570, S590, S630, S650, S750, S770, T550, T590, T630, T650, T750, T770, and T870 models.
Common causes of M4902
- Feedback wire 6200/3440 or 6200/6230 shorted to a supply voltage
- Faulty rear work lights relay
- Faulty gateway controller
- Moisture, corrosion, or pushed-back pins in the gateway controller connectors, rear light relay connectors, tailgate connector, tailgate harness, or mainframe harness
- Intermittent fault where the condition is not present at time of testing, which can come from loose connections, corrosion, pushed-back pins, the controller, the wire harness, or a combination of these
How to troubleshoot Bobcat M4902: first checks
- Turn the key switch to run/enter and confirm the code is active, since that is the condition required for the code to set
- Inspect the tailgate connector and tailgate harness for moisture, corrosion, or pushed-back pins
- Check the gateway controller connectors and rear light relay connectors for the same issues
- Backprobe feedback wire 3440 or 6230 (whichever applies to the model) and check for unexpected voltage when the rear lights are not commanded on
- Inspect the mainframe harness for chafing or pinch points that could cause the feedback wire to short to a supply voltage
- Test or swap the rear work lights relay if wiring checks out clean
- If the code does not reproduce during testing, treat it as intermittent and focus on connector corrosion, loose pins, and harness condition since these are the most likely causes of an intermittent fault
How the code clears
Once the repair is complete, cycle the key power to clear the code. No separate clearing step is listed beyond a power cycle.
Affected models and serial ranges
M4902 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 M4902 mean?
It means the gateway controller detected voltage on the rear light feedback wire (3440 or 6230 depending on the model) at a time when the rear lights were not commanded on. This points to a wiring or relay issue in the rear light circuit.
Will M4902 stop my Bobcat from running?
The description does not indicate M4902 disables machine operation. It is a feedback fault on the rear light circuit rather than a drive or engine safety code.
What is the panel number for M4902?
The numeric panel form of this code is 49-02.
Which Bobcat models can show M4902?
It applies to the S510, S530, S550, S570, S590, S630, S650, S750, S770, T550, T590, T630, T650, T750, T770, and T870.
How do I clear M4902 after fixing it?
Cycle the key power. No other clearing procedure is listed for this code.
Why does M4902 come and go instead of staying on?
Intermittent behavior usually points to loose connections, corrosion, or pushed-back pins in the connectors along the rear light circuit rather than a fully failed component. If the fault isn't present when you test, focus your inspection on connector condition and harness routing.
Is M4902 the same as a blown rear light bulb?
No. This code is about the feedback wire seeing voltage it shouldn't, which relates to the relay and wiring circuit, not a burned out bulb.