Q: What Are Reprogrammable Car ECUs?

asked by on December 01, 2015

What are reprogrammable car ECUs?

Service Light is on Inspection $79.99 - $89.99 Get a Quote

An electronic control unit (ECU) is comprised of many different computer parts soldered onto a circuit board to make up a complete ECU. The ECU uses different kinds of memory on its computer board. These memory chips are used for different reasons and work in different ways. Some computer chips are designed to be reprogrammable and others are not. Some memory chips will keep their memory as long as power is supplied to them and others will keep their memory even if power is removed or lost.

The memory in a car’s computer ECU that holds the programming to control the running of your engine is called EEPROM or electrically erasable programmable read only memory. This memory can be programmed and reprogrammed electrically to be able to upgrade or change the programming that controls the engine functions. The chip is most commonly used for a vehicle’s calibration file to operate the engine within specifications of the manufacturer. It is a non volatile chip meaning it will keep its memory even if power is lost. The chip can be reprogrammed to change the calibration if changes are needed.

Another computer chip called ROM, or read only memory, can only be programmed once. It cannot be reprogrammed once it is programmed. This memory is used to perform basic computer operating functions only and will not be changed even if power is removed the same as the EEPROM. The ROM will store basic memory functions to operate the onboard diagnostics and other basic functions that do not need reprogramming. https://www.yourmechanic.com/services/service-light-is-on-inspection

The reprogrammability of the ECU memory has been around for over 15 years in vehicles and is used extensively in different modules and ECUs throughout the vehicle. This memory is used in transmission, ABS, body, engine, suspension, AC, ride control and other ECU modules of today’s vehicles. This memory is very reliable and rarely fails. If the program put on it is bad or needs updating, then it can be electronically erased and the new program installed. Once it is installed, the new program can be used as needed. If the chip itself has internal failures, the ROM can detect this since it checks the EPROM every time you turn on your key. If errors are found, then a code is set into the computer storage memory chip or another EEPROM.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

What others are asking

Back up camera comes on and off when my headlights are on

The navigation unit and power train control unit use some common sensors to know when you are in reverse to activate the backup camera. If your backup lights do not work or other problems are happening, then I suggest having...

Need car diagnosed.

I would call YourMechanic to come and diagnose this problem.

check engine light on, code p0016 and p0017 shown

Of course, after a repair be sure to erase the codes. If the same codes do return after erasure, then there is a continuing, unresolved problem. Diagnostic Trouble Code P0016 and Diagnostic Trouble Code P0017 have multiple causes including that...

How Does a Battery Work With a Car's Electrical System?

One of the most recognized mechanical parts under the hood of any vehicle is the battery. Whether you're an ASE certified master mechanic or have never turned a wrench, everybody can pinpoint the location of their vehicle's battery. Although most...

Gauges and Radio flicker when driving

This could be caused by a faulty power steering cooling fan. The Mini's have an electrically controlled fan that will de-activate power assist if the fluid temperature exceeds a programmed standard to prevent damage to the power steering system. These...

voltage warning light still coming on 30-45 seconds after car starts.

Nothing should be replaced until you have in hand a definitive diagnostic pinpointing the faulty segment of the car's electrical system. There may be too much voltage drop in the charging circuit, as well as elsewhere, but start with the...

Ignition and fuse box burned up

Electrical issues are something that definitely should be assessed by a technician. The fuse box may in fact still be intact but depending on what happened, you could need wiring harnesses, terminal repairs, etc. Wiring that is routed improperly, of...

Car starts but will not run

You should not replace any parts, at all, unless the part is diagnosed as not functioning. ECU's rarely fail (fully 50% of warranty returns on ECU's have absolutely nothing wrong with them). If there is a spark at the plug...

At 60 mph tachometer fluctuates between 3000 and red line

Hello. The Electric Code Detector is a component of the fuse block that detects increased electrical power needed and increases the idle speed to allow the alternator to provide more power. There is a specific test from Honda to determine...

Related articles

How Can I Tell If the OBD System Is Working Correctly?
Today’s Today’s cars are far more sophisticated than they once were, and they require a computer to monitor and manage the various systems so that everything works together properly. This also gives you the means to determine if there’s something...
How Does Adjustable Suspension Work?
Every Every vehicle’s suspension — the collection of parts that supports it, cushions its load from bumps, and enables it to turn — represents a compromise by the designers. Automakers must consider numerous factors in design any vehicle’s suspension, including:...
How Does Adjustable Suspension Work?
Every Every vehicle’s suspension — the collection of parts that supports it, cushions its load from bumps, and enables it to turn — represents a compromise by the designers. Automakers must consider numerous factors in design any vehicle’s suspension, including:...