CAT Engine 5485 Fault Code: Throttle Lock Lamp open circuit
Also called Throttle Lock Lamp Current Below Normal, Throttle Lock Lamp Open Circuit
Throttle Lock Lamp open circuit · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT code 5485 means the ECM has detected current below normal, an open circuit, or a short to +Battery on the throttle lock lamp circuit after the ECM has been powered for at least 2 seconds. It is an indicator lamp fault, not a fault in the throttle lock function itself, though it can make it harder to know when throttle lock is active.
Low severity. This code affects an indicator lamp circuit, not engine control or the throttle lock feature's core logic. It should be diagnosed when convenient, but it is not an immediate safety or drivability emergency by itself.
What does CAT Engine error code 5485 mean?
Code 5485 is set when the ECM sees the throttle lock lamp circuit reporting current below normal, an open circuit, or a short to +Battery. The ECM must have been powered up for at least 2 seconds before it will log the fault.
The throttle lock feature lets an operator hold a set engine rpm without using the throttle pedal. A rocker switch turns the feature on and off, and the throttle lock lamp lights up when it is active. Two push buttons, Set/Decel and Resume/Accel, adjust the held rpm up or down, and pressing the right brake pedal disables the feature. If the ECM sees invalid signals from the right brake switch, it will disable throttle lock until the keyswitch is cycled from OFF to ON.
Code 5485 itself is only about the lamp circuit that reports throttle lock status to the operator. It does not directly disable the throttle lock feature, but a bad lamp circuit means the operator may not get a reliable visual signal that throttle lock is engaged.
What triggers a CAT Engine 5485 code?
The ECM logs this code when it detects current below normal on the throttle lock lamp circuit, or when it detects an open circuit or a short to +Battery condition, provided the ECM has been powered up for at least 2 seconds.
Common causes of 5485
- Damaged, corroded, or loose connectors and wiring in the throttle lock lamp circuit
- A problem with the wiring harness feeding the lamp
- A burned out or faulty throttle lock lamp bulb
- A faulty lamp socket
- A faulty throttle lock ON/OFF switch
- An intermittent connection problem that only shows up under vibration or temperature changes
- A faulty main power relay
- A faulty ECM
How to troubleshoot CAT Engine 5485: first checks
- Visually inspect the throttle lock lamp bulb and socket for damage, corrosion, or a burned-out element
- Check all connectors and wiring in the throttle lock lamp circuit for damage, corrosion, or loose pins
- Wiggle-test the harness near the lamp and switch while watching for the code to reset, to catch an intermittent fault
- Inspect the throttle lock ON/OFF switch for proper operation and secure wiring connections
- Check the main power relay for proper operation if wiring and lamp checks are clean
- Use a diagnostic scan tool or display module to confirm the active code and check for related stored codes before replacing parts
How the code clears
No separate clearing step is listed. Once the underlying wiring, lamp, socket, switch, relay, or ECM issue is repaired, the code should stop being active. Confirm on a diagnostic scan tool or display module that the code no longer shows as active after repairs.
Frequently asked questions
What does CAT code 5485 mean?
It means the ECM detected current below normal, an open circuit, or a short to +Battery on the throttle lock lamp circuit after being powered for at least 2 seconds. It is a lamp circuit fault, not a failure of the throttle lock function itself.
Will code 5485 disable my throttle lock feature?
Not by itself. This code is about the indicator lamp circuit. The throttle lock feature is disabled separately by the ECM if signals from the right brake switch are invalid, and it stays disabled until the keyswitch is cycled from OFF to ON.
Is it safe to keep driving with this code active?
Yes, in most cases, since this is an indicator lamp issue rather than an engine control or braking fault. However, without a working lamp you may not know when throttle lock is engaged, so treat it as a maintenance item to fix soon.
What parts commonly cause code 5485?
Damaged connectors or wiring, a bad bulb, a faulty lamp socket, a faulty throttle lock ON/OFF switch, an intermittent connection, a faulty main power relay, or a faulty ECM are all listed as possible causes.
How do I know if it's the bulb or the wiring?
Start by visually inspecting the bulb and socket for damage or burnout. If those look fine, check the connectors and wiring for corrosion or loose connections, and wiggle-test the harness while monitoring for the code to reappear, since intermittent wiring problems are a listed cause.
Does cycling the key clear code 5485?
No separate clearing step is listed for this code. Cycling the keyswitch from OFF to ON does clear a disabled throttle lock feature caused by an invalid brake switch signal, but that is a different condition from code 5485 itself.