Bobcat M1503 (15-03) Fault Code: Traction Lock Pull Output Error Off
Also shown on the panel as 15-03
Traction Lock Pull Output Error Off · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
M1503 (panel code 15-03) sets when Bobcat's gateway controller commands the traction lock pull output on wire 4110 but does not see voltage return on that circuit. When this happens, traction is disabled until the fault is corrected and power is cycled.
High severity. Traction is disabled whenever this code is active, which stops the machine from driving. It is not an engine-damage emergency, but it is a stop-work fault because the loader cannot move until it is resolved.
What does Bobcat error code M1503 mean?
M1503 is set by the gateway controller when it commands the traction lock pull output, wire 4110, to energize the traction pull relay, but does not detect voltage on that wire as expected. The traction pull relay is what allows the machine's traction system to be enabled, so if the controller cannot confirm the output is working, it will not trust the traction circuit.
Because traction control is a core safety and drivability function, Bobcat's logic disables traction outright when this code is active. The machine will not drive until the wiring or controller fault is corrected and power is cycled.
This is an electrical output/feedback fault, not a hydraulic pump or valve failure. The root cause lives in the wiring, connectors, or the gateway controller itself.
Common causes of M1503
- Controller output wire 4110 shorted to ground
- Gateway controller fault
- Moisture, corrosion, or pushed back pins in the gateway controller connectors, traction lock relay connectors, or the mainframe wire harness
- Loose connections in the affected wiring or connectors
- Intermittent faults that may not be present or reproducible at the time of testing, caused by any combination of loose connections, corrosion, pushed back pins, the controller, or the wire harness
How to troubleshoot Bobcat M1503: first checks
- Confirm the key switch is in run/enter, the seat bar is down, and Press To Operate Loader (PTOL) is enabled, since these are the conditions under which the controller expects the traction lock pull output to be active
- Inspect wire 4110 for chafing, pinching, or a short to ground along its full run from the gateway controller to the traction lock relay
- Check the gateway controller connectors and the traction lock relay connectors for moisture, corrosion, or pins that have been pushed back out of their sockets
- Inspect the mainframe wire harness connectors in the same circuit for the same conditions: moisture, corrosion, or pushed-back pins
- Wiggle-test connectors and wiring while watching for the fault to reappear if the code was intermittent and not active at the time of inspection
- If wiring and connectors check out, suspect the gateway controller itself as the cause
How the code clears
Once the wiring, connector, or controller issue is repaired, cycle power (turn the key off and back on) to clear the code. No separate clearing step is listed beyond a power cycle.
Affected models and serial ranges
M1503 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 M1503 mean?
It means the gateway controller commanded the traction lock pull output on wire 4110 to turn on, but did not detect voltage on that circuit as expected. Traction is disabled as a result.
Can I still drive my Bobcat with M1503 active?
No. Once M1503 sets, the loader's traction is disabled until the fault is fixed and power is cycled.
What is the traction lock pull output on wire 4110?
It is the output from the gateway controller that energizes the traction pull relay, which is what enables traction on the machine when commanded.
What usually causes M1503?
A short to ground on wire 4110, a faulty gateway controller, or moisture, corrosion, or pushed-back pins in the gateway controller, traction lock relay, or mainframe harness connectors are the listed causes.
How do I clear code M1503 after repair?
Cycle power on the machine (key off, then back on) once the wiring or connector issue is repaired. No other clearing procedure is listed.
Why does M1503 come and go instead of staying on?
Intermittent versions of this code point to loose connections, corrosion, or pushed-back pins that only cause a fault under certain conditions like vibration or moisture. If the fault is not active during testing, the exact cause may not be identifiable until it reoccurs.
Which Bobcat models can show code M1503?
This code applies to the S510, S530, S550, S570, S590, S630, S650, S750, S770, T550, T590, T630, T650, T750, and T770/T870 model lines.