Wiring Codes and identification of sensors and actuators

Hi all,

I am relatively new to this and looking to learn more about my car and to clean up some previous work completed by a previous owner. I’m interested in rewiring my EFI system but I’d like to research a little more about identifying the components before I pull the harness off the engine. Is there a recommended way to identify what sensors are what? I have a service manual for the car, would that be the best place to start with identifying components of the EFI system?

I have got the wiring fundamentals and practical club level course and I see that on the map there are codes like RSINJ etc. Is there anywhere I could find a list of universally recognised codes so I can learn what they all are and label my harness accordingly before it’s removed from the car?

Cheers,

Taylor

Hey Taylor,

Great to hear you’re getting into the wiring side of things, it can definitely feel daunting at first, but it’s absolutely worth it.

A good workshop/service manual for your specific vehicle is usually the best place to start. If you’ve got access to proper wiring diagrams, I’d suggest starting at the ECU and tracing each circuit one by one. It’s a bit of a time investment, but it gives you a really clear understanding of where everything goes, how circuits branch, and ultimately what each component is.

More importantly, it helps you understand how the system works as a whole. That understanding becomes invaluable later on when diagnosing issues or modifying the system.

If you get stuck, a bit of research based on where a component is located or what it’s connected to can go a long way, there’s usually decent info out there with some digging.

Another really useful resource is OEM parts catalogues like Amayama. They’ve got excellent exploded diagrams for a lot of vehicles, which can help you visually identify components and see how they fit into the system. For example, I recently picked up a ’97 Toyota Caldina and came across what looked like an actuator in the rear quarter panel. A quick look through the parts catalogue showed it was actually part of a factory variable exhaust system, something I wouldn’t have guessed otherwise.

As for the labeling codes, there isn’t really a universal standard, most of the time they’re just logical abbreviations based on the circuit function.

The trick is to look at the wiring map as a whole and spot patterns. For example, if you see labels like RSINJ grouped with similar names, and others like FLIGN or RLIGN nearby, you can start to break it down:

“INJ”, injector circuits

“IGN”, ignition circuits

Then the prefixes usually describe position or function. In a rotary engine, for example:

FP, Front Primary, FS, Front Secondary injectors

RP, Rear Primary, RS, Rear Secondary injectors

FL, Front Leading, FT, Front Trailing ignition

RL, Rear Leading, RT, Rear Trailing ignition

So RSINJ becomes “Rear Secondary Injector”, and FLIGN becomes “Front Leading Ignition”.

At a glance it can look like gibberish, but once you start recognising patterns across the diagram, it becomes much easier to decode.

When it comes to labeling your own harness, just keep it simple and consistent, clear abbreviations or short descriptions work best. For example:

Intake Air Temp, IAT

Manifold Pressure, MAP

Fuel Pressure, FUEL P

Power Supply, PWR

That way anyone (including future you) can quickly understand what’s going on.