What an OEM number is
An OEM part number is the manufacturer's own catalogue reference for a specific component in a specific application. It is not the same as the number the component's original supplier — Bosch, Denso, Valeo, Delphi and so on — puts on the same part. Both are useful; the OEM number is the one that ties the part to your vehicle.
You will often find both printed on the same label, which is why a photograph beats transcribing by hand.
Common formats in India
- Hyundai and Kia. Typically ten or eleven characters, often written with a hyphen after the fifth — for example
37300-2B101. The first block indicates the part family, the second the application. - Maruti Suzuki. Usually formatted as
31400-M74L00— a five-digit group, then an alphanumeric group. - Toyota. Five digits, then five, sometimes with a suffix:
27060-0L090. - Volkswagen, Skoda and Audi. The familiar nine-character group-of-three format, often with a letter index:
03L 903 023 F. The middle group indicates the assembly group. - Honda. Typically three groups, such as
31100-RNA-A01, where the middle group identifies the engine or platform. - Mahindra, Tata and others. Formats vary more; numbers are often stamped directly rather than printed.
Do not worry about getting the format right. Photograph what you see and send it.
Where to look, component by component
Alternator
On the body near a mounting ear, or on the rear cover. Frequently a printed label alongside a separate supplier label giving voltage and amperage. Both are worth capturing.
Starter motor
Usually on the main housing between the solenoid and the motor body, sometimes stamped into the casting rather than printed.
AC compressor
On the compressor body, often on the flat face near the ports. Commonly obscured by road grime — clean it gently before photographing. A second label may give refrigerant type and oil specification.
ECU and control modules
On the case, typically as several numbers together: the OEM hardware number, a supplier number, and a software or coding index. All of them matter for a control unit, so photograph the whole label rather than one line of it.
Headlights and tail lights
Moulded into the plastic housing on the rear face, usually near the bulb access or the mounting tabs, alongside approval markings such as an E-mark.
Body panels
Often stamped or stickered on an inner face — the underside of a bonnet, the inner face of a door skin, or behind a bumper mounting.
Sensors
Printed on the body or on the connector shroud. On small sensors the print is fine and wears off easily; a macro photograph in good light is worth the effort.
Hold a phone torch almost parallel to the surface rather than pointing straight at it. Raking light throws stamped characters into relief and makes them readable when a flat flash washes them out. Photograph, then zoom into the photograph — the camera usually sees more than your eye at that angle.
Superseded numbers
Manufacturers replace part numbers over time. A number stamped on a part fitted in 2013 may have been superseded once or twice since. The superseding part is generally the correct replacement, but not always interchangeable in both directions. If your number does not appear to match anything current, that is usually why — and it is a normal situation, not a problem.
What to do when there is no number
This is common on parts that have been in service for years, and it is not a dead end. Physical identification works: connector shape and pin count, pulley diameter and groove count, mounting pattern, overall dimensions, and the vehicle specification together will usually get to a single answer.
Send photographs and your vehicle details. This guide covers exactly which photographs help most.
A note on VIN
Your VIN identifies your specific vehicle and its build specification. Manufacturer dealer systems can look up exact part numbers from it. Independent access to those systems varies, so treat VIN-based lookup as helpful where it is available rather than something to rely on.