Bobcat M1806 (18-06) Fault Code: Lift Spool Lock Short to Ground
Also shown on the panel as 18-06 · Also called Lift Spool Lock Output Short to Ground
Lift Spool Lock Short to Ground · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
M1806 (panel code 18-06) sets when the gateway controller cannot detect voltage on the lift spool lock solenoid circuit, either on signal wire 4680 / return wire 2680, or on signal wire 4380 / return wire 2380 depending on the machine's harness configuration. When it sets, lift and tilt functions are disabled until the fault is corrected.
High severity. Lift and tilt are disabled the moment this code sets, which stops loader work entirely. It is not a safety-shutdown-of-the-engine event, but it is a functional stoppage that needs same-shift attention since the machine cannot do its job until it clears.
What does Bobcat error code M1806 mean?
M1806 is set by the gateway controller when it expects to see voltage on the lift spool lock solenoid circuit and does not find it. Depending on the specific machine's wiring, this circuit runs on either signal wire 4680 with return wire 2680, or signal wire 4380 with return wire 2380. Both versions of the fault behave the same way and disable lift and tilt functions as a protective response.
The lift spool lock solenoid is part of the hydraulic control system that governs whether the lift and tilt spools can move. If the controller loses confidence in this circuit, most likely because it looks shorted to ground, it locks out lift and tilt rather than risk uncontrolled or unintended movement.
This is functionally a wiring and solenoid circuit fault, not a hydraulic pressure or pump problem. The fix almost always centers on the harness, the connectors, the solenoid itself, or the gateway controller.
Common causes of M1806
- Signal wire (4680 or 4380) or its matching return wire (2680 or 2380) shorted to ground.
- A faulty lift spool lock solenoid.
- A fault in the gateway controller itself.
- Moisture, corrosion, or pushed-back pins in the mainframe harness connectors.
- An intermittent condition: if the code is not active at the time of testing, the root cause may not be found right away. Loose connections, corrosion, pushed-back pins, the controller, the wire harness, or a combination of these can all be involved.
How to troubleshoot Bobcat M1806: first checks
- Confirm the key switch is in run/enter and the seatbar is down, since these are the required conditions for the code to be active and for you to test accurately.
- Visually inspect the mainframe harness connectors near the lift spool lock solenoid for moisture, corrosion, or pins that have been pushed back out of their sockets.
- Check the signal wire and return wire for your machine's configuration (4680/2680 or 4380/2380) for signs of chafing or shorting to a ground point along the harness routing.
- Test the lift spool lock solenoid itself for correct operation, since a failed solenoid can present as this code.
- If the code is not currently active, treat it as intermittent: recheck all connectors and wiring for loose or corroded terminals even if nothing looks obviously wrong at first glance.
- Inspect or test the gateway controller connections if wiring and solenoid check out, since the controller itself is listed as a possible cause.
How the code clears
Once the repair is complete, cycle power to the machine (key off, then key on) to clear the code. No separate clearing step is listed beyond cycling power.
Affected models and serial ranges
M1806 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 M1806 mean?
It means the gateway controller could not detect voltage on the lift spool lock solenoid circuit, either on wires 4680/2680 or 4380/2380 depending on your machine. This disables lift and tilt functions until the fault is fixed and power is cycled.
Why did my loader's lift and tilt stop working?
If M1806 is active, the controller has disabled lift and tilt as a protective measure because it cannot confirm the lift spool lock solenoid circuit is working correctly, often due to a short to ground.
What is the lift spool lock solenoid for?
It is part of the hydraulic control circuit that locks or unlocks the lift and tilt spools. The gateway controller monitors voltage on this solenoid's circuit to confirm it is functioning before allowing lift and tilt movement.
Can corrosion in the wiring cause M1806?
Yes. Moisture, corrosion, or pushed-back pins in the mainframe harness connectors are listed as a possible cause, and are common with intermittent versions of this code.
How do I clear M1806 after I fix it?
Cycle power to the machine, key off and then back on. No other clearing procedure is listed.
Why can't I find the cause of M1806 during testing?
If the fault is intermittent and not active when you test, the root cause may not show up right away. Loose connections, corrosion, pushed-back pins, the controller, or the wire harness can all be involved individually or in combination.
Which Bobcat models can get code M1806?
It appears across 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, and T770.