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Introduction

For the most part, what's going on inside your cars computer (ECU, or Engine Control Unit) is hidden from you and fairly hard to monitor. There are however, a few outputs from the ECU that are pretty easy to monitor. This page gives some basic information that should be helpful in connecting a simple monitor to these outputs. Additional details, such as how to get to the ECU, part numbers, etc., are available at Damian Sigman's Knock Sensor page.

Disclaimer....

I assume no liability for any actions attempted because of the information on this page. Incorrect implementation could void warranties, damage your cars ECU, maybe cause engine damage, and ruin your day! While I'm trying to make the information on this page correct and clear, it is not guaranteed to be so. The service manual is very useful for finding the correct wires! email me.

Now for the fun stuff!

The type of outputs that are easy to monitor are those that control solenoids. But.....

What's a solenoid?

It's an electrically controlled valve. It can be open or closed, and in the case of our cars, is used to route engine vacuum or boost pressure to different actuators used in controlling the engine.

What do these solenoids do?

There are one to four solenoids on your T/E/L, depending on the model.

• Purge control solenoid (all models)
  This is part of the emissions system. A charcoal canister absorbs fuel vapors when the engine isn't running. When is running, the ECU turns this solenoid on, which opens a valve which allows vapors from the canister to be drawn into the engine to be burned.

• Waste gate solenoid (turbo models only)
  This is used to lower the maximum amount of boost the turbo produces. If the ECU detects knocking (using...you guess'd it, a knock sensor!), the ignition timing is retarded. If the engine is still knocking and the timing has been retarded the maximum amount, the ECU turns this solenoid off, lowering the maximum amount of boost to a value lower than if the solenoid where on.

• Fuel purge control solenoid (turbo models only)
  This one is used to temporarily increase the fuel pressure in the fuel rail. This is done to lower the possibility of vapor forming in the fuel line on hot days when the engine is warm. This solenoid is normally off, except when the ECU senses that it's a 'warm' day, and that the engine is warmed up based on the coolant temperature.

• EGR solenoid (CA models only)
  Another part of the emissions control. To lower combustion temperatures (and therefore lower the amount of NOx formed, an air pollutant), under certain conditions some of the exhaust gas is recirculated back through the engine and reburned. This is only done under partial throttle, and the amount of recirculation is controlled by switching the solenoid on and off with a variable duty cycle.

Enough tech stuff!

Why do this?

I added these monitors because I wanted to see some of the basic behavoir of the ECU. The only one of these that gives real useful info is the waste gate solenoid. This tells you if the ECU is lowering the amount of boost, which is not fun!. This can be due to many things, the simplest being low octane gas.

Why would you want to add these? For fun, maybe you like LED's blinking, or are just curious.

Finally, how do I do it?

First you need to decide how to mount the LED's, where they're going to go, where the wires will go, etc. I have mine in a plastic box, and the wire connections are socketed so it's not a permanent addition to my car's interior.

You will also need to get access to your ECU's wires. This is easier if you have a VPC.

Here's a schematic. The wires are identified using the convention used in the service manual. The letter identifies the wiring section ("C" means the dash panel). The number after the letter identifies the specific connector. The number after the dash tells you the specific wire.

Jason Neal was nice enough to email me the connections for the 2G cars. They are:

				Wire	Color
Wastegate solenoid		11	R-Y
Fuel pressure solenoid		3	L-R
Evaporative emission purge	9	LG-B
EGR				6	LG-R

To reiterate what's written above:

On Damian's Knock Sensor page, he chose to have the LED light when the solenoid was off; my schematic has the LED light when the solenoid is on. Either case probably works equally as well. It's just a matter of personal preference.

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