What’s the benefit of drive by wire?

Just a random question since there’s nothing on tv and I’m not asleep. What’s the purpose of drive by wire? Technological advances are great, if they improve something. But I don’t see the improvement here. Were throttle cables that problematic? Are the drive by wire components cheaper to manufacture than a throttle position sensor and cable? I don’t see improved throttle response as a benefit…at least not in the F150 I drove. It almost seemed like the computer had to take a second to think and recognize that I’d pushed the accelerator down 3/4 of the way. Almost like turbo lag, but it was a V8 truck. I assume there’s some obvious benefit of DBW that I’m overlooking.

I googled it. Apparently the benefits are emissions and safety related as best I can tell. The computer can read other inputs before allowing the throttle to open to the commanded position, if it deems that this would allow more efficient operation. As for safety, apparently it aids with traction control, etc. Seems like a lot of tech and complication for seemingly not a ton on benefit for the end user. I’m thinking I’d be wishing for a throttle cable if my electronic throttle body ever goes bad in my future vehicle.

The benefit is simplicity. Why have three or more components and systems when one will do?

Start your car on a cold morning and the idle speed needs to be higher. Turn on the A/C at idle and the engine needs more rpm to handle the load. Let off the throttle suddenly on the freeway and the engine speed needs to be reduced gradually to avoid stalling. All these functions were controlled by an Idle Air Control Valve. Drive by wire eliminates the IAC and can perform all these functions by simply operating the throttle body to control RPM.

Cruise control required an additional linkage or cable attached to the throttle, not to mention vacuum and electric sources to operate the cruise control servo that maintained the desired speed by opening and closing the throttle. Not to mention the additional vacuum and/or electrical circuits integrated into the brake switch system to cut off the cruise control when you tap the brake pedal. Drive by wire eliminates all this and allows the car to operate the cruise control simply through the throttle body.

Vehicle Stability Control, which your next car is required by law to have, requires the ability to control throttle application. The older stability control systems that used a throttle cable to the gas pedal were a complicated mess and seemed to cause as many problems as they were intended to solve. An electronic throttle solves this problem.


Excellent reply by @asemaster.

I’d add an MPG improvement for those drivers that pump the accelerator pedal like they are pumping the gas into the engine! The ECU can “learn” this behavior and filter it out.

I traded a 2002 Chevy truck for a 2004. The 2004 DBW version got 7% better economy than the 2002 wired throttle truck with the same engine, transmission and gear ratios. There may have been other changes not apparent, but outwardly everything appeared the same.


With DBW (Drive by Wire), a computer can be inserted between the driver and the engine, thereby allowing the computer to override the driver’s input. This may be useful in a number of ways:

  1. Traction Control: The computer can throttle back the engine torque to prevent slipping tires. Add ABS (antilock braking systems) and this makes the car less likely to lose traction and spin out. The computer can react in milliseconds to situations - much faster than a human can!

  2. Efficiency: Having the computer in the loop means a better link to the transmission for optimum performance. Yes, the throttle position sensor is used for this, but not as precisely.

  3. The engine would be a bit easier to package in the car. Throttle cables can’t have kinks, plus they have all sorts of linkages that make the engine s bit more difficult to fit in the space.

And to counter what the OP said: Computers react in milliseconds - much faster than a human can. No, there would be LESS lag, the opposite of what was stated. Turbo lag? The computer could help there as well. There are algorithms that can anticipate the driver’s input, making driver’s input a bit faster.

Do not get me wrong. I am not a big fan of installing DBW until the kinks have been worked out. All too often, car manufacturers rush something out that is problematic.


Those are all good technical reasons, I’ll add another I didn’t see mentioned- it’s cheaper to build that way. Labor is expensive. Installing cables and other doodads like IACs cost a lot of money in labor and parts. Plugging in a couple connectors beats that hands down. And a wire harness instead of those expensive parts…win-win for the manufacturer.


There are several advantages to computer-controlled throttle position, including increased fuel efficiency. Another is that the computer can alter throttle position based on variable timing of both spark and valves. In fact, the throttle position can be finely adjusted based on all types of conditions, including ambient temperature, humidity, etc.

Let me add here! It might be quite easier to maintain at the long run.

You should consider you might be attributing that lag to the wrong part. If this truck was an automatic, mashing the accelerator like that can cause the automatic transmission to downshift.

Even if the improvement is only a few MPG, improving a truck’s fuel economy from 18 to 20 MPG saves about 56 gallons of fuel per 10,000 miles driven, while improving a car’s fuel economy from 33 to 35 MPG only saves about 17 gallons of fuel per 10,000 miles driven. A 2 MPG improvement on a big truck saves a lot more fuel than a 2 MPG improvement on a small car.

It’s easy to eschew the benefits of traction control, until you need it.

The primary benefit is to the manufacturer. It’s cheaper to produce.

Secondary benefit is a teeny-tiny improvement in gas mileage due to slightly lower weight. Pretty soon the fed requirements will get so bad that manufacturers will have to remove seats. They’re already removing spare tires.

Tertiary benefits include the ability to have the vehicle parallel park itself, maintain its place in its proper lane on the road, and other technical byproducts having to do with modern technology.

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Why is it that so many people think they know better than the vehicle’s manufacturer? :rofl:

The same reason why people think Dr. Google and Dr. WebMD are better than seeing an actual Physician/CRNP/PA-C

Sorry, that was kind of an inside joke. MB made that comment in an oil thread and I was mocking him.

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No worries, I recall the comment :slight_smile:

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If you’re talking Steer-by-wire then I agree. But throttle-by-wire…NO. Throttle-by-wire has some very clear advantages in that the computer takes control of air/gas mix. Much more accurate which allows for measurable increases in gas mileage.

The computer has taken control of the air/fuel mix since computer controlled carbs in the 80’s and every fuel injected vehicle since.

Drive by wire just takes by-wire control of the throttle plate itself. The mixture is determined by closing the loop on the O2 sensor readings (and coolant temp, mass-airflow readings, manifold pressure and lots more) and a look-up fuel map when running open-loop mode.

Open loop is used prior to the O2 sensor warming up and being able to feed information back to the ECU. Also open loop can be used on full-throttle events to richen the mixture to lower than 14.7:1 for additional power in engines for short bursts. Or for when one or more sensors fail and the engine drops into “limp-home” mode.

But I agree whole-heartedly on DBW’s affect on fuel economy.

I will agree with @Scrapyard_John that some drive by wire systems have an unacceptable amount of “lag”, at least for spirited drivers. Subarus in particular in my opinion. The throttle response on those cars reminds me of an old 50’s fluid drive transmission. Push the throttle down and wait for something to happen. If you want to peel away from a traffic light or zoom up a freeway ramp in front of another car, good luck. I have found that disabling the traction control system in these cars seems to offer improvement.

I was, in fact, thinking of steer by wire when I posted.
But I have to point out that fuel metering was driven by the ECU well before pedal-by-wire became common. Even when the throttle was still pulled by cable the ECU was metering by sensor inputs, the throttle position as pulled by the cable and represented to the ECU via the throttle position sensor being only one.

Good discussion. I don’t quite grasp what dbw and an ecm can do that a throttle position sensor and an ecm can’t do just yet. I’ll have to think about it.

Or it might very well cost you more money to replace… who knows. I will say, I’ve had to replace exactly one throttle cable on any vehicle I’ve owned. And it was a 4wd mud truck that was sold as scrap metal.