DiagnosticsMedium severity

Bobcat M7748 (77-48) Fault Code: Key Switch Multiple

Also shown on the panel as 77-48

Key Switch Multiple · ai-assisted, editor-reviewed · Last updated 2026-07-13

TL;DR

M7748, shown as 77-48 on the panel, sets when the gateway controller sees voltage on two separate key switch input wires at the same time: one from the right display panel and one from the diagnostic tool/ACD connector. It points to a wiring or connector problem, or both key switches being on at once, not a mechanical failure.

Medium severity. M7748 will not damage the machine by itself, but it signals a wiring or controller input conflict that can affect key switch/run-enter logic and diagnostic tool communication. It should be diagnosed before it causes intermittent no-start or no-communication issues.

What does Bobcat error code M7748 mean?

M7748, also shown as 77-48 on the display panel, is a Bobcat gateway controller fault called Key Switch Multiple. The gateway controller has two separate input lines that both report key switch/run-enter status: one comes from the right display panel (wire 9350 or 3040 depending on the machine's wiring version), and the other comes from the diagnostic tool/ACD connector (wire 9400 or 3090 depending on version).

The gateway controller expects only one of these lines to be active at a time under normal operation. When it detects voltage on both the display panel input and the diagnostic tool/ACD input at the same time, it sets M7748.

This is a logic conflict code rather than a code tied to a specific broken part. It can be caused by both key switches genuinely being on together, a wiring short that feeds supply voltage into the wrong line, a bad connector, or a failing display panel or diagnostic tool.

What triggers a Bobcat M7748 code?

The code sets when the key switch/(run/enter) is on and the gateway controller reads voltage present on both the right display panel input wire (9350 or 3040) and the diagnostic tool/ACD connector input wire (9400 or 3090) at the same time.

Common causes of M7748

The right panel key switch/(run/enter) is on at the same time the diagnostic tool's key switch/(run/enter) is on.
The remote key wire (9400 or 3090) or the run/enter wire (9350 or 3040) is shorted to supply voltage.
A fault in the diagnostic tool itself.
A fault in the right display panel itself.
Moisture, corrosion, or pushed-back pins in the gateway controller connectors, ACD connector, right display panel connector, diagnostic tool harness, mainframe harness, or cab harness.
An intermittent condition: if the code is not active at the time of testing, the cause may not be found immediately. Likely culprits in that case include loose connections, corrosion, pushed-back pins, the controller itself, the wire harness, or a combination of these.

How to troubleshoot Bobcat M7748: first checks

Confirm whether a diagnostic tool is connected and powered on at the same time as the machine's key switch. Disconnect the diagnostic tool and see if the code clears after a power cycle.
Inspect the right display panel connector and the ACD/diagnostic tool connector for moisture, corrosion, or pins that have pushed back out of the connector body.
Check the mainframe harness and cab harness along the run of wires 9350/3040 and 9400/3090 for chafing, pinched sections, or shorts to supply voltage.
Test the remote key wire (9400 or 3090) and the run/enter wire (9350 or 3040) for an unwanted short to battery/supply voltage.
If the code is not active when you test, treat it as intermittent: recheck all connectors for looseness or corrosion and consider whether the controller or harness itself needs closer inspection or replacement.
Swap or bench-test the diagnostic tool if you suspect it is feeding a false signal into the ACD connector line.

How the code clears

Cycle the key switch power after completing repairs. No separate clearing step is listed beyond a power cycle.

Affected models and serial ranges

M7748 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

Safety-critical: confirm before use

Electrical safety: stop the engine before inspecting wiring, fuses, connectors, or drive belts, and avoid shorting power terminals. Thresholds, component locations, wire numbers, fuse locations, and reset procedures can vary by model, configuration, and serial number. Confirm them in the service documentation for your exact machine.

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Frequently asked questions

What does Bobcat code M7748 mean?

It means the gateway controller detected voltage on two separate key switch input wires at the same time: one from the right display panel and one from the diagnostic tool/ACD connector. Bobcat labels this Key Switch Multiple.

Is M7748 the same as 77-48 on the display?

Yes. 77-48 is the numeric panel form of the same fault code M7748.

Will M7748 stop my Bobcat from running?

The code itself is a wiring/logic conflict, not a listed engine or hydraulic shutdown. However, it should be diagnosed promptly since it involves the key switch and run/enter circuits that other systems rely on.

Why does M7748 show up when I connect a diagnostic tool?

If both the right display panel's key switch input and the diagnostic tool/ACD connector's input are active at the same time, the gateway controller sees two conflicting signals and sets the code. Disconnecting the diagnostic tool and cycling power is a good first test.

How do I clear M7748 after fixing it?

Cycle the key switch power. No other clearing procedure is listed for this code.

What if the code is intermittent and doesn't show up during testing?

If M7748 is not active when you check, the root cause may not be found right away. Likely suspects include loose connections, corrosion, pushed-back pins in connectors, the wire harness, or the gateway controller itself.

Which Bobcat models can show code M7748?

It applies to S510, S530, S550, S570, S590, S630, S650, S750, S770, T550, T590, T630, T650, T750, T770, and T870 models.