I haven’t actually done this, but, of course, I have looked into it and I have some thoughts to share about it.

The Cruise Control system on the Corsica consists of several different pieces:

• The ECM or the car’s “computer”
• The Cruise Control module
• The speed sensor (ECM may do this in late-model cars)
• The throttle control stepper motor and throttle linkage cable
• The Cruise Control controls, mounted on turn-signal stick on steering column
• The brake switch
• The clutch switch (manual transmission only)

As you can see the Cruise setup is pretty complicated, and adding Cruise Control to a car that left the factory without it is complicated.

How it works

An electronic, or “stepper”, motor is attached to the throttle control, in parallel with the gas pedal. In this way, either the Cruise Control stepper motor or the gas pedal controls the amount of air, and therefore gas, the engine receives.

The Cruise Control module controls the stepper motor, and therefore, the speed of the engine. When the car is first turned on, the Cruise Control motor is turned all the way “down”, so that only the gas pedal controls the speed of the engine.

When the Cruise Control is engaged by putting the Cruise Control switch in the “On” position and pressing the button on the end on the end of the turn signal stick, the Cruise Control module reads the car’s speed from either an external speed sensor, or from the car’s ECM. The module then turns the stepper motor to a location where it thinks the right speed should be. When you let off the gas to let the Cruise Control do it’s job, the motor holds the throttle where you left it. This makes the car keep a constant speed.

It’s a bit more complex that that, though. For example, if you go up a hill but don’t give the engine more throttle, the car will slow down. This is universally true, because it always takes more energy to go up a hill than to go down a hill or go over a level surface.

The Cruise Control module handles this situation by operating in closed-loop mode. By this technical mumbo-jumbo, I simply mean that the Cruise Control module is constantly re-checking the speed of the car to see if it is correct. If the speed is too low, the Cruise Control module uses the stepper motor to give the engine more throttle. If the speed is too high, the engine receives less throttle. However, this is done pretty slowly, so the car isn’t constantly jerking around.

(You can ignore this paragraph. It’s just me ranting.) By the way, I don’t particularly care for GM’s implementation of Cruise Control, on the L-Bodies, anyway. Because it is a closed loop system, it falls prey to a number of technical things. Anyone who took any classes on Closed-Loop Systems, Feedback Systems, etc., in college will tell you that these things are pretty complex, and I think GM didn’t quite make the grade. Specifically, the V6 engine is suddenly thrown into WOT (wide-open throttle) whenever vehicle speed drops quickly. This might be necessary on the I4 (inline four cylinder) cars, where power isn’t available at low RPMs, but on the V6 it is quite annoying. I guess they use the same Cruise Control module on both the I4 and V6 engines, for cost reasons. Someday I hope to implement my own cruise control module that handles this much better. If and when this happens, I will document it here thoroughly.

The brake and clutch switches are used to detect when the brake and or clutch is pressed. When the Cruise Control module detects either pedal being pressed, it immediately turns off the Cruise Control. This makes sense since if you are hitting the brakes, you don’t want the engine to keep trying to push the car forward. If you are hitting the clutch, it probably means you are shifting, and keeping the engine speed constant doesn’t make sense.

The RA (Resume Acceleration, whatever that means) switch setting allows you to go back to your previously set speed, after you have turned off the Cruise Control in some way (switch, brakes, clutch). For example, let’s says that you are driving at 65 mph, and you come upon a truck turning off, and you have to slow down. You hit the brakes, the cruise control turns off, and your car slows. Now the truck has turned and is out of the way, so you momentarily push the Cruise Control switch into the RA area. When you let go of the switch, it pops nack into On. The Cruise Control module then uses the stepper motor to give the engine more throttle until the car reaches 65 mph again.

You may not know that you can also adjust your cruise speed on the fly by using the RA section of the Cruise Control switch and the Cruise Control button. To set your speed higher, press and hold the Cruise Control switch into RA, and your car will speed up. When you let go, your vehicle will stay at it’s current speed. To drop your cruising speed, press and hold the Cruise Control button on the end of the turn signal stick. Again, when you let go of the button, your car will stay at it’s current speed. An as example, let’s use the turning truck again. Let’s say you have your cruise control set for 65 mph, and you see the truck ahead turning. You decide that you are far enough away that you don’t need to stop, but you should slow down. You hit the Cruise Control button on the end of the turn signal stick, and your vehicle slows. You let go when your car has slowed to 40 mph, and the Cruise Control module maintains this speed. In this hypothetical situation, this speed allows plenty of time for the truck to turn before you reach it. When the truck has turned off the road, you press and hold the Cruise Control switch into RA, and your vehicle speeds up again, until you reach 65 mph, where you release the button, and your car maintains 65 mph. You’ve slowed and sped up again, all without ever touching the gas pedal!

Where everything is

Here is a list of locations of each component of the Cruise Control system for the Chevy Corsica:

Adding cruise

You will need to purchase the Cruise Control module, stepper motor, switch and button controls for the turn signal stick, and possibly the speed sensor, if you have an older car. You should try to get these items from a salvage yard as they will be much cheaper than if you buy them from a GM dealer.

The first thing to add is the stepper motor and throttle linkage. Be sure to purchase the throttle linkage with the stepper motor!

The stepper motor bolts on to the firewall, in the direction of the passenger side from the brake master cylinder. The holes for mounting are already tapped in my car, so it’s a simply case of the bolting the stepper motor bracket on the firewall.

Next, connect the throttle linkage from the stepper motor to the throttle cable bracket. There should be an empty spot next to the throttle cable where the cruise cable can go in the bracket. If not, you will have to go back to the salvage yard and get one of these brackets.

The cruise cable attached to the little wheel beside the main throttle cable wheel. All you have to do is slide the cruise cable into it’s slot on the bracket, and put the ball on the end of the cable into it’s slot on the wheel.

Next you have to take the dash off. This sucks. You need to do this to put in the cruise module. It also makes it easier to drill a hole through the firewall to run the wires from the stepper motor to the cruise module. Unfortunately, we won’t cover taking out the dash here because it’s it’s a huge pain. You will need to take off the steering wheel (and therefore, airbag), and probably at least one door, both seats and the center console. Not pretty.

There are at least two wires that you have to run from the ECM, located behind the glove box, to the cruise module in the dash. You also have to connect the wires from the stepper motor to the cruise module, after you have drilled your hole in the firewall.

While you have the dash off, you should also add switches to your brake and clutch (if necessary) pedals. Run wires from these switches to the cruise module.

While you have the steering column apart, you should replace your turn signal stick with one that has the Cruise Control buttons on it. Run the wires from the Cruise Control buttons down the column, and when you put the column back in, plug them into the cruise module.