How to Clear Fault Codes on Cummins INSITE

By Parts Online Team On Sep 29, 2026 0

To clear fault codes on Cummins INSITE, connect to the ECM, open the Fault Codes window, right-click inside it, choose Refresh All Faults, and then click All. Only codes marked Inactive will clear — an active fault that the controller still detects cannot be erased until you repair the underlying problem — and INSITE requires a key cycle after clearing before the result is confirmed.

That is the short answer. In practice, clearing codes is the easy part. The reason codes refuse to clear, come straight back, or leave the engine in a derate is almost always that the fault itself is still present. This guide walks through the exact INSITE sequence, explains what INSITE will and will not erase, and covers the errors people run into most often.

Quick Answer: The Clearing Sequence

Connect. Plug in your RP1210 adapter, key on, and let INSITE detect the ECM.
Open the Fault Codes window. Active codes are listed first, inactive codes after them.
Record before you erase. Print or screenshot the list — clearing also wipes the history.
Repair the cause. Clearing a live fault only hides it until the next key cycle.
Clear the codes. Right-click in the fault code window, select Refresh All Faults, then click All.
Key cycle. Key off, wait, key on — INSITE asks for this after clearing.
Verify. Re-read the ECM. Anything still listed is a fault that is still there.

If the connection itself is where you usually get stuck, our walkthrough of how to install Cummins INSITE covers adapter drivers and folder setup in more depth.

Why INSITE Only Clears Inactive Codes

The ECM keeps two fault lists. Active codes are faults the controller is detecting right now. Inactive codes are faults that occurred at some point but are not present at this moment — history rather than a live problem.

By design, the ECM will not let a diagnostic tool erase a fault it is currently seeing. If it did, the warning lamp would go dark while the fault continued to damage the engine, which is the opposite of what a diagnostic system is for. So the sequence is always the same: the fault disappears or is repaired first, the code drops to inactive, and only then can you clear it.

That means the real question is rarely “how do I clear this code” but “why is this code still active”. If you are still identifying what the numbers mean, our Cummins INSITE fault code reference for SPN and FMI explains how to read the pairs and where to start looking.

Active, Inactive and Permanent Codes

Status	What it means	Can INSITE clear it?
Active	The ECM is detecting the fault right now	No — repair the fault first, then it goes inactive
Inactive	The fault occurred but is not present now	Yes — this is exactly what the clear function targets
Permanent / latched	Held by emissions or protection logic	Only partly — it clears itself once the required conditions are met

Step-by-Step: Clearing Codes in Cummins INSITE

1. Establish the ECM connection

Key on with the engine off and plug the adapter into the diagnostic port. In INSITE, select the correct adapter and connection type, then let the application detect the controller. Multi-module engines present a primary and a secondary ECM — make sure you are looking at the module that actually owns the code. Adapter choice matters more than most people expect, and our roundup of adapters and cables for Cummins INSITE covers the interface differences.

2. Open the Fault Codes window

The Fault Codes window lists active faults first, then inactive ones, each with its SPN, FMI, count and a short description. Read the active entries carefully before touching anything — they tell you what the engine is complaining about right now.

3. Fix the fault before you clear it

This is the step that decides whether the code stays gone. Diagnose the active faults, repair the cause, and run the engine long enough to confirm the fault no longer sets. Only then does clearing do anything useful.

4. Clear the codes

Right-click inside the fault code window, choose Refresh All Faults, then click All. If you only want to remove specific entries, select them first and use the selected-clear option instead. INSITE reports what it cleared and what it could not.

5. Perform a key cycle

INSITE requires a key cycle after clearing fault codes. Switch the key off, wait at least 30 seconds, and switch it back on. The ECM rebuilds its fault list on the power cycle, which is why skipping this step makes it look as though nothing happened.

6. Re-scan and confirm

Re-read the fault list. Codes that were genuinely repaired stay cleared. Anything that reappears immediately was never fixed — you are now looking at an active fault again, not a failed clear.

The Key Cycle: The Step Most People Skip

A key cycle is not the same as driving the truck. For most faults it is simply key off, a short pause, key on. But a key cycle will not clear everything: emissions and aftertreatment faults often need a full operating cycle — a drive at temperature through the right speed and load range — before the controller will retire them. If a code survives a key cycle but the repair is genuinely done, drive the vehicle normally and recheck rather than clearing it repeatedly.

Common Errors When Clearing Codes

Symptom	Likely cause	What to do
Code reappears straight after clearing	The fault is still active	Go back to diagnosis; clearing cannot fix a live fault
Clear option has no effect	The window has not been refreshed	Right-click → Refresh All Faults before clearing
Settings appear greyed out	No ECM connection, or the module is protected	Recheck the connection and the ECM security access level
Codes clear but the engine stays derated	A derate latch is held in the controller	Complete the repair and the required operating cycle
Codes return after a key cycle	An intermittent fault that has not been found yet	Log a live session and monitor while the fault is active
Nothing can be changed on one module	ECM security — read-only mode	Data can be viewed, but changes need the required access level

Codes That Will Not Clear — and Why

Still active. The most common reason. Repair, then clear.
Intermittent. The fault is not present at the moment you clear it, but the condition returns under load, heat or vibration, so the code comes back.
Emissions and aftertreatment. These often retire only after the controller sees the correct operating cycle, not a key cycle.
ECM security. If the required access level is not supplied, INSITE stays in read-only mode for that module and write functions are unavailable.
Protection latches. Some faults hold a derate until the repair is complete and confirmed by the controller.

Do You Need INSITE to Clear the Codes?

Clearing codes needs a bidirectional tool — one that can both read and command the controller. Many basic code readers are read-only and will show a code without being able to erase it. Unplugging the batteries is not a clearing method either; the fault simply returns the next time the ECM sees the condition.

The value of INSITE is that it is the manufacturer’s own tool: it reads faults with correct SPN/FMI descriptions and follows them with guided troubleshooting. If you work across both brands, our comparison of CAT ET vs Cummins INSITE explains how the two platforms differ in daily use.

Does Clearing Codes Fix the Engine?

No. Clearing codes is a diagnostic step, not a repair. It tidies the fault list once you have dealt with the cause and gives you a clean baseline to confirm the fix. If a code comes back, the underlying fault is still there — clearing it again achieves nothing except losing the history you might need.

Which INSITE Edition Do You Need?

Reading and clearing fault codes works across the INSITE editions — it is core diagnostics, not an upgrade feature. The editions differ in what they can write to the controller, most notably whether calibration download is available, and ECM security can still limit write access on a protected module. Our guide to Cummins INSITE Lite sets out exactly where those boundaries sit.

Frequently Asked Questions

Can INSITE clear active fault codes?

No. Only inactive codes can be cleared. An active code means the controller is detecting the fault right now, so it must be repaired before it can be erased.

Do I have to do a key cycle after clearing codes?

Yes. INSITE requires a key cycle after clearing. Switch the key off, pause, then key on so the ECM rebuilds its fault list and the clear is confirmed.

Will disconnecting the battery clear Cummins fault codes?

No. Pulling power does not permanently clear Cummins fault codes. The fault returns as soon as the ECM sees the condition again, and you lose the history in the process.

Can a basic code reader clear the codes?

Only if it is bidirectional. Many inexpensive readers are read-only and can display a code without erasing it. Bidirectional diagnostic software is what actually performs the clear.

Why does the same code come back after clearing?

Because the fault is still present, or it is intermittent and returns under the conditions that caused it. Clearing a code never fixes the fault that set it.

Is it safe to clear fault codes?

Yes, once you have recorded them and repaired the cause. Just clear after you have written the list down — the history is the clue you need if the fault comes back.