The INSITE cylinder cutout test switches off one injector at a time on a Cummins engine. As a result, you can see which cylinder does less work than the others. It is one of the fastest ways to find a weak injector, a misfire or a low-compression cylinder.
When to use the INSITE cylinder cutout test
A rough idle, white smoke, a misfire or a knock often comes from one cylinder. However, guessing which one costs time and parts. Instead, the test lets the ECM compare every cylinder under the same conditions.
When the tool cuts a healthy cylinder, the engine needs more fuel to hold the speed. When it cuts a weak one, almost nothing changes. Therefore, the cylinder with the smallest change is your suspect.
What you need before you start
- A Windows 10 or 11 Pro 64-bit laptop with the software installed and activated
- Cummins INSITE with a licence level that includes the cylinder performance tests
- A supported RP1210 adapter, such as a NEXIQ USB-Link or a Noregon DLA, with the correct 9-pin or 16-pin cable
- Engine at operating temperature
- All accessories, such as the A/C and the PTO, switched off
Run the test with the truck parked, the parking brake on and the transmission in neutral. Also, keep hands away from the fan and the belts.
How to run the INSITE cylinder cutout test
- First, connect the adapter and start the engine.
- Then open INSITE and connect to the ECM.
- Next, read the fault codes and note any injector codes.
- After that, open the ECM diagnostic tests and the cylinder performance group.
- Now choose the automatic cylinder cutout test, or the single cylinder cutout if you suspect one cylinder.
- Start the test and let the engine run at the requested speed.
- Finally, read the result table for each cylinder.
Compare the fuelling change for each cylinder. If one cylinder shows a much smaller change, check its injector, its valve lash and its compression before you replace parts.
How to read INSITE cylinder cutout test results
One cylinder shows little change. That cylinder contributes less power. So check the injector, the valves and the compression.
Two neighbouring cylinders are weak. This often points to a head gasket leak between them.
Every cylinder looks similar but the engine still runs rough. Then look elsewhere, for example at the fuel supply, the air intake or a sensor.
The test will not start. Usually the engine is too cold, or an accessory load is on. Therefore, warm it up and switch off the loads.
Get Cummins INSITE on your laptop
We install Cummins INSITE remotely on your own Windows laptop with TeamViewer or AnyDesk, and we test it before we finish. Each installation includes 12 months of support. Also, you get a full refund if we cannot make it work on the setup we confirmed with you; see our refund policy. For the maker’s own documents, visit the official Cummins website.
To see real installations first, watch our YouTube channel DIAGTECHPRO INSTALLATION. Then message us on WhatsApp at +84 963 975 864 or email di4gtechpro@gmail.com, and tell us the vehicle, the engine and your adapter.
Related guides on DiagTechPro
- Bidirectional Controls and Active Diagnostic Tests
- Injector Trim Coding: Purpose and Workshop Checks
- Reading and Clearing Fault Codes with Cummins INSITE
- Reading Truck Live Data: Beyond Fault Codes
Questions about INSITE cylinder cutout test
Is the INSITE cylinder cutout test safe for the engine?
Yes. The ECM runs it under controlled conditions, and it only takes a few minutes.
Does it find a bad injector for sure?
It shows the weak cylinder. Then you confirm the cause with an injector test or a compression test.
Which INSITE version do I need?
Recent engines need INSITE 8 or newer. Tell us the engine, and we will confirm the version.
