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LML - P0420, P2463, P24A0

Texas Diesel Company has the factory GM computer in-house! This allows us to quickly and effectively diagnose your vehicle saving you both time and money. We are also able to provide in-house programming of all components & modules installed in your vehicle, no different than the Chevrolet/GMC dealership would. If you’re another local shop interested in having us re-program a module for you, please call (903) 292-0400

All of these codes refer back to the Hydrocarbon Injector. This injector is also known as the “9th injector”. We see quite a few of these in our shop and here is the best way we have found to diagnose the issue.


o Start by running the truck until operating temperature is reached. The vehicle coolant and oil needs to be at least 180 degrees. In many cases, we see that the LML have thermostat failure unknown to the owner. When the truck cannot reach operating temperature on its own (coolant gauge isn’t reading in the middle for those without a scan tool) the vehicle will not enter into regen mode. This is the first step of diagnosing an HCI issue. Make sure and fix this issue and then perform a manual regen. Check to make sure that the EGT 1 and EGT 2 temperatures are reaching their desired limits.

o If the truck is running within the operating temperature, attempt to put the truck into manual regeneration. After about 5 minutes, you should see your EGT 1 sensor rise above 600° degrees Fahrenheit and your EGT 2 temperature rise above 1000° Fahrenheit. If this is not the case most likely you will need a new HCI injector.


▪ To test this theory, remove the HCI injector from the exhaust. Energize the HCI using your scan tool with the truck running, you should see diesel being sprayed from the injector. If no diesel is coming out then it’s likely the HCI injector has failed.

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