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ECU (Engine Control Unit)

Related articles

How Your ECU Uses Sensor Data
Today’s modern vehicles are made up of anywhere from one to seven computers that assist with the car’s day to day functions. An engine control unit (ECU), is a computer that similar to that of...
What Is a Reprogrammable ECU?
The ECU, or engine control unit, is part of your car’s computerized brain and is responsible for monitoring and managing all aspects of engine operation. For anyone who isn’t interested in upgrading their...
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Related questions

Question
Can I get a high output alternator for my car for putting in a bigger amplifier?
Hello. There are aftermarket alternators on the market that you should check the internet for kits for this vehicle so you can install the larger amp. You may find that this large of an amp may require a second battery...
Question
Air conditioning light - 2001 Honda Civic
Hi there, check the A/C relay for being stuck in the "On" position. Relay contacts degrade over time and use, and can stick together when burned. The result would be the A/C light staying on, even though you press the...
Question
Pcm ecu car won't start
Assuming the ECM is still working enough to report problems, getting any problem codes out of the system with a code reader is your best clue at this point - whether the Check Engine Light is illuminated or not. If...
Question
Check Engine Light does not come on even though there are trouble codes present
The pink/light green wire in ECM pin 2 on the connector will ground the wire internally to the ECM to turn on the Check Engine Light. You could test the wire with the key on and it should have battery...
Question
Intermittently doesn't start
Hi there. There could be several reasons for your vehicle's intermittent no start issue. From the description you have given, I would not think the ECU (electronic control unit) is your vehicle's problem. Assuming the ECU is not recognizing the...
Question
When trying to start it only clicks on a large relay (?ECU?) under the dash passenger side.
Often times when there is a starting issue, there is a small part called a starter relay that is many times over looked that is usually a fairly simple and inexpensive fix. The starter relay is a small unit near...
Question
If a mechanic put one of the fuel injectors in the wrong cylinder, could this damage the ECU?
Hello. The ECU could not have been damaged by moving injectors to different cylinders. The injectors are not programmed to be in a particular cylinder of the engine. Having only two injectors reconditioned is the most likely cause for running...
Question
Missing/Broken ECU - 1989 BMW 325i
If your ECM is failing or has failed, it shouldn't be extremely difficult to find a good shop to rebuild or replace them. There are a number of electronic rebuilders who rebuild ECMs (w/warranty). Also, there are a number of...
Question
Hello, my car has no spark, no controlled ground for the fuel pump, and no injector pulse. Fuse link close to the battery and relays are good.
Hello and thank you for contacting YourMechanic. The ECU is under your passenger's side seat. You can gain access to it by simply sliding the seat all the way forward and removing the plastic cover from the ECU. You can...
Question
Traction control light is on, 2000 BMW
As you know, your car is equipped with wheel speed sensors at each of the four wheels which monitor wheel speed while relaying this information constantly to the ABS and traction control system which are controlled by the car's ECU....
Question
can I use the positive and negative posts under the hood to maintain power to the computer while replacing main battery
If the two posts are indeed specified for jump starting, then the answer is "yes" you can safely install a 12 volt car battery there at the remote posts while you remove and replace the permanent car battery. Electrically, all...
Question
module or unit?
Hi there. From the description you have provided, your vehicle Check Engine Light on with lots of warnings and exterior lighting acting weird, sounds like there may be a charging system related problem. I would recommend not driving your vehicle...
Question
It won't start and the ECU is not found by scanner.
Hi there. First check the battery and make sure that there is 12.6 volts. If the battery is low, then the battery will need charged before testing again. Check the wiring from the battery to the fuse box and make...
Question
Will a bad O2 sensor damage my car's computer?
The engine control unit (ECU) is a possible cause of the O2 sensor fault codes but not the most likely. Your vehicle is equipped with 4 O2 sensors. Bank 1 is the driver's side. Bank 2 is the passenger side....
Question
Replaced ECU Integrated Transfer Case Board, how much will it cost to reprogram it?
Hey there, thanks for writing in about your 2006 Land Rover LR3. Unfortunately, this is a specialized service only available through Land Rover service centers, and not a cost estimate readily available to us here at YourMechanic. I recommend requesting...
Question
My car has crank and no start issues.
There is one thing I don't think you have listed or have checked. That would be injector pulse. You can have fuel pressure but without injector pulse from the ECU, the injectors will not open and the cylinders will not...
Question
ECU disconnected
Hi and thanks for contacting YourMechanic. First, remove the ground cable from the battery and let it stay off for 12 minutes. Then hook up the battery cable and retry the key. If your vehicle still gives you the same...
Question
How long can it take an ECU computer to go bad?
Hello, and thank you for writing in. The vehicle likely did not suddenly develop all of these problems. Oil leaks in particular happen due to excessive engine wear. The spark plugs and their coils tend to be regular maintenance with...
Question
Q: question
The security system warning light should not illuminate once the vehicle is started and you are driving. If the light does illuminate, that means there is a malfunction in the security system. Obviously, if this problem started immediately after you...
Question
After replacing the ECM in a 2002 Mercury Mountaineer what will be the reason for it not to fire or start
On cars built after the late 1990's, replacing an ECU is a much bigger deal than just plugging in a new box. The ECU has to recognize the serial number of the car and the other modules in the car....

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