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When you go to buy a used car or truck, one question that you will want to answer is whether or not the engine is original to the vehicle. Reputable auto dealers will include this information in the car explanation. A good way to check this yourself is to compare the Vehicle's Information Number (VIN) and the car/truck's Engine Serial Number (ESN).
Every car or truck is manufactured with a Vehicle Information Number (VIN) and an Engine Serial Number (ESN). The VIN is usually found on the dashboard near the windshield. The ESN is either stamped on the engine block itself or written on a metal plate that is bolted to the engine block.
Keep reading to learn more about your car or truck's identifying serial numbers and where to find them. You will discover how to know if the engine is original or a replacement. You will learn how to decode the different serial numbers to learn about your vehicle's engine and the vehicle's assembly location and year.
What Serial Numbers Does a Vehicle Have?
Cars and trucks before the mid-1990s have two main serial numbers: the Vehicle Information Number and the Engine Serial Number.
Cars and trucks after the mid-1990s have an added Engine Family Number (EFN) which is for the Environmental Protection Agency's sorting of engines for emissions.
What is the Engine Serial Number?
The ESN is an individual number either stamped onto the engine block or on the engine plate bolted to the block. Auto manufacturers can put the ESN anywhere on the engine block.
The ESN tells you what engine it is, when and where it was made, and a unique number for this exact engine.
Read more: 12 Types Of Car Engines [And How They Work]
Is the engine serial number the same as VIN?
The ESN is not the same as the VIN. The ESN is the code that identifies information about the engine's manufacturing. The VIN identifies the entire vehicle in its original state.
How to Find the Engine Serial Number
The best place to start is with your vehicle's owner's manual. The ESN is often in the first few pages of the manual along with a picture of where it is found on the engine block.
If the ESN is not easily found, check the index in the back of the manual for the Engine Serial Number, which will bring you to the correct page with its location.
Finding the Engine Serial Number Location Without a Manual
For a used vehicle where the owner's manual may not be original, or if you don't have it, go to the automaker's website and search for the Engine Serial Number location.
You can also find many videos showing where the ESN is for different auto makes, models, and production years.
For example, here is one such video for finding the ESN on a Volvo engine.
Reading the Engine Serial Number on the Engine Block
When you know the ESN's location, you will need a flashlight, shop towel, cell phone camera, and possibly a solvent like an engine oil for cleaning the metal. Open the hood, making sure it is secure in the up position. A good light makes this process much easier.
Find the stamp of the engine plate and clean it if needed with the solvent so that it is legible. Then snap a pic so you can enlarge it for easier reading.
What Does the Engine Serial Number Tell You?
The ESN includes lots of important information about the engine. When decoded, the ESN shows the automaker of the engine and the specific plant. It tells you the month and year of assembly.
It can tell you about boring, liters, and other specifications of that particular engine.
Decoding the ESN
The ESN is a series of digits (numbers and letters) with spaces. The digits are different per each automotive company. Most give the following information (the order changes by manufacturer):
- A digit identifying the country that manufactured the vehicle
- A digit identifying the automotive manufacturer
- 1-2 digits identifying the plant that made the engine
- 3-4 digits identifying the type of engine
- 1-3 digits telling what month, year, and sometimes, the exact day the factory assembled the engine
- 3-4 digits giving details about the engine's specifications
Once you have your ESN, you can use the automaker's parts website to help find parts for that engine. When you enter the ESN do not include the spaces in the search bar.
How can I tell if my car engine is original?
Once you have the ESN, compare it to the VIN's last six letters. They should be the same. If they are different, the engine is not the Original Equipment Manufacturer's (OEM) engine. The engine is a replacement.
What is the Vehicle Information Number - VIN?
Every vehicle has a unique VIN. The automotive companies use the standard order on the VIN, so the information is easier to decode. The Department of Motor Vehicles and law enforcement use the VIN to identify a vehicle and its legal owner.
Where to Find the VIN?
You can find the VIN in multiple locations on a vehicle. The two easiest to find locations are:
- On the driver's side of the dashboard, close to the base of the front windshield
- Printed on a sticker label on the driver's door
Decoding the VIN
The VIN has 17 digits that tell a lot about the vehicle. Some countries refer to the chassis number rather than call it a VIN. Beginning on the left, here is what the digits mean:
- 1st Digit - Country code
- 2nd Digit - Auto manufacturer
- 3rd Digit - Manufacturer division
- 4th Digit - Safety braking type
- 5th Digit - Series
- 6-7th Digits - Chassis type
- 8th Digit - Engine type
- 9th Digit - Check type
- 10th Digit - A letter denoting the manufacturing decade
- 11th Digit - The year designated by 0-9
- 12th Digit - The manufacturing plant code
- 13-17th Digits - The unique production number
Note: The 12th-17th digits are a part of the ESN.
Does the VIN change when the engine is replaced?
The VIN never changes for the life of the vehicle. Since the VIN does not change, you must find the actual ESN on the engine block to compare it with the last six digits of the VIN to see if they match. Different numbers mean a different engine.
How do I find the manufacture date of my engine?
The best place to start is by looking up the VIN in a decoder. To get even more information, find the ESN for your engine and look up what it means for all the specifications of your engine.
You can find the month and year of manufacturing on the VIN for the entire vehicle and the ESN for the engine's assembly.
What is the Engine Family Number?
Since the mid-1990s, vehicles in the United States have had an assigned Engine Family Number (EFN), also called a Test Group, which gives the engine type and its emission standards. The EPA uses the EFN to classify each vehicle's emissions when the vehicle is tested.
Read more: Do Catalytic Converters Have Serial Numbers?
The Emission Control System Label
The EPA requires all vehicles in the United States to have an Emission Control System, also called the Vehicle Emission Control Information label, stuck to the radiator support or underneath the hood.
This label will have the EFN prominently listed. Most automotive manufacturers include the vehicle's full ESN into the Engine Family Number on this label.
If you are the original owner of the vehicle, you can trust the ESN found on this label without having to find the ESN on the engine block itself.
All vehicles have an Engine Serial Number and a Vehicle Information Number. The ESN identifies the specific engine and some of its specifications. The VIN is the unique number identifying each exact vehicle.
The ESN can be difficult to locate on the engine block itself. Fortunately, the ESN is printed on the Emission Control System sticker label and in the Owner's Manual.