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HomeTips & GuidesSkip Shift: How This Computer-Aided Gear Selection System Works

Skip Shift: How This Computer-Aided Gear Selection System Works

Skip Shift or shift blocking is a manual transmission feature built into GM vehicles manufactured in the late 80s. 

Although the feature helps enhance the car’s fuel economy, its implementation has been controversial.

Most people install Skip Shift eliminators in their vehicles to remove this forced control. 

After all, people buying manual transmission vehicles want total control. Let’s define this feature and all you need to know about it. Take a look!

Table of Contents

What Is Skip Shift?

Introduced in the Chevy Corvette in 1989, Skip Shift came with the name Computer-Aided Gear Selection (CAGS). This manual transmission feature improves the fuel economy ratings in the CAFE (Corporate Average Fuel Economy) system.

It works by preventing the normal shifting to second or third from first gear. Instead, the system forces you to shift to fourth gear from first. Higher gears have lower torque but make the engine burn less fuel.

How Skip Shift Works

This gear prevention occurs when the parameters allow. For instance, the throttle should be about 35% or lower. With the throttle at this position, the speed should be between 15 and 21 mph.

How a 5-speed manual transmission works

How a 5-speed manual transmission works

Also, the car’s coolant/engine temperature must be 171°F (77°C) or higher for the Skip Shift system to kick in. But the specifics can vary slightly depending on the vehicle.

In a nutshell, the system can only kick in under low acceleration and engine load conditions. It consists of the following components.

When you turn on the ignition, power from the battery goes directly to the Skip Shift solenoid. The computer (PCM) controls power flow to the solenoid by grounding its control circuit. At this point (ignition turn on), it does not ground the system. Therefore, the system is inactive.

When the skip-shift solenoid is active, the PCM also grounds the Skip Shift lamp, making it turn on. This dashboard light informs you the 1-4 Skip Shift system is on.

But when the vehicle meets the abovementioned parameters, the PCM grounds the Skip Shift solenoid. This solenoid mechanically blocks the gear shift lever from engaging 2nd and 3rd gear positions.

A vector image of a manual transmission

A vector image of a manual transmission

Deactivation Conditions

The deactivation conditions for this computer-controlled solenoid are when your vehicle’s conditions fall outside the activation limits. These include when:

  • The throttle opens wide enough
  • Car exceeds typical city driving speeds

In some vehicles, the PCM fails to re-engage skip-shifting until you stop. So, it will only kick in when you start again from zero. But the vehicle should meet the abovementioned conditions.

An engine control module

An engine control module

This shift-blocking feature is typical in GM vehicle brands like Cadillac, Pontiac, Chevrolet, Dodge, and Holden.

What About Skip Shifting When Downshifting?

The regular way to downshift is 4th to 3rd, 2nd, then 1st gear. But you can downshift directly from 4th to 2nd. This second method is still skip shifting because you don’t go through the intermediary gears.

The benefit of this process is you get to do less work, which minimizes the possibility of making errors.

A cross-section of a vehicle’s manual gearbox

A cross-section of a vehicle’s manual gearbox

However, the computer-controlled solenoid does not handle this downshift skip shifting because it does not improve the fuel economy. So, you can call this “manual” skip shifting.

And the downside is you can over-slow your vehicle or over-rev the engine because it is challenging to get the timing right.

Skip Shift Eliminator

Fuel economy is not a priority if buying a muscle car like the Dodge Challenger or a sports vehicle like the Corvette. All you are looking for is performance and a driving thrill.

Manual transmission rebuilding

Manual transmission rebuilding

Plus, manual vehicle drivers buy the cars to have total control over the driving process. Therefore, most car owners eliminate this feature if it is present in their vehicles.

Luckily, the elimination process is relatively easy because the eliminator is a plug-in piece.

How To Install the Skip Shift Eliminator

As stated earlier, the Skip Shift system consists of the PCM, Skip Shift solenoid, and Skip Shift light. Depending on the manufacturer, the plug-in piece can operate differently. But most simulate the presence of an active Skip Shift solenoid.

You only have to plug this eliminator into the engine harness on the end that connects to the solenoid.

Unplug the solenoid on the transmission’s PCM harness and link the eliminator. This device is simply a resistor that tricks the PCM into believing the load (solenoid) is on and active.

Therefore, the PCM will still scan the vehicle. It will ground the solenoid’s control circuit when the conditions turn true. The resistor simulates a load, tricking the computer.

The dashboard light will still turn on to indicate the system is active, but the solenoid will be offline. So, it won’t mechanically block the 2nd and 3rd gears.

Regular shifting in a manual transmission without skipping 2nd and 3rd gears

Regular shifting in a manual transmission without skipping 2nd and 3rd gears

And the vehicle won’t turn on the check engine or Service Engine Soon (SES) lights.

Wrap Up

Although the Skip Shift feature came about to improve fuel economy in vehicles, it hasn’t gone down well with customers. The skip from 1st to 4th gear doesn’t hurt the engine or gearbox but can cause low torque acceleration.

This driving experience goes against what driving enthusiasts buying sports or muscle cars want. Luckily, you can bypass the system. 

Contact us if you want to diy your car; we can help you get wiring harnesses at reasonable prices.

Hi I am Christa, sales manager of Cloom.

I have extensive expertise and experience in wiring harnesses and I believe I can help you.

And we have a very professional technical team who can clearly understand the customer’s needs and give professional suggestions and solutions after receiving the drawings.

If you also have wiring harness needs, please send me the drawing so that we can give you our quote and start our business.

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