Electronic Control Unit. The vehicle computer which controls the functions of the engine based upon input from various sensors. The ECU adjusts different aspects of the engine. PCM, PCU, and ECM can all be considered synonyms.

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Peculiar Interior Lighting Issue

Recently a friend of mine was driving a VW Fox (not new, I'm not sure what year but it was certainly 5+ years old) home in the dark with the lights on. Strangely, after a minute or two of driving all ...
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38 views

Response to 2001 Toyota Carolla vvt code 1349: what should I do?

I got a vvt 1349 code on my 2001 Toyota Carolla. I have noticed a sharp decrease in fuel economy. Some people have reported that the oil control valve may be causing the issue. The oil control valve ...
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71 views

What is the cost/benefit for reprogramming an ECU for a non-enthusiast?

As I've been learning more about cars, I keep hearing about how manufacturers are conservative with ECU settings. For someone who isn't into racing, but would like a bit better performance out of his ...
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35 views

Mazda 3 2011 1.6 Lts Gasoline - ECU

I was wondering if its possible for a Mazda 3 2011 AT car to function without ECU? The reason I am asking is When I start the engine, the CheckEngineLight doesnot come at all When I took my car for ...
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141 views

LTFT and STFT values are off and don't make sense

Car is a 2015 BMW M5 and it has an aftermarket CAI and a catback (slip on) exhaust. No other performance mods or tunes. About 6-7 months ago, I bought a Kiwi OBD-II reader, simply out of curiosity ...
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39 views

2009 Aprilia RSV1000 - Piggy Back ECU, Should I get one?

I have an Aprilia Tuono, 2009. It seems to run lean after putting an Akrapovic exhaust on it. It makes exhaust popping sounds on deceleration. My boyfriend said I need a power commander on it to ...
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47 views

How do I pull error codes from my Kawasaki motorcycle?

I have an FI light on my Kawasaki motorcycle that is 2002 or newer. How do I get the error codes so I can troubleshoot it?
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1answer
82 views

Determining active gear from OBD2 for Ford Fiesta

I am trying to to write an app which advises the driver to change gears and do some other driving quality assessments. For this purpose I need to determine the RPM and currently active gear in a ...
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62 views

Letting Off Gas Forces Open Loop

I noticed something that seems a bit strange to me. Many times when I let off the gas the ECU drops out of closed loop into open loop for about a second. You can see on the graph that this happens ...
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53 views

Fuel Economy Gauge Modification

I have a little digital screen in my dash that re-evaluates my average fuel consumption (L/100km) every thirty seconds. How can I modify this to increase the reporting frequency? Preferably, at least ...
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101 views

How is barometric pressure related to emissions testing?

In the VW emissions cheating scandal, news reports say the following: According to the EPA, "the position of the steering wheel, vehicle speed, the duration of the engine's operation, and barometric ...
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124 views

ECU replacing procedures

In a Renault Laguna 1.6 2003 , the ECU got damaged physically (the connector went off ) so i have to replace it with another one ( used ECU ) , I've read that I will need to disable the Immobilizer ...
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45 views

Chiptuning for a car with DPF (Diesel Particulate Filter) is a bad idea?

I know that it is possible to disable DPF (Diesel Particulate Filter). I'm wondering how bad it could be to leave DPF (Diesel Particulate Filter) functioning and add a chip to a car?
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99 views

Where are ECUs and for which tasks are they used? [closed]

ECUs are "Electronic Control Units". I've heard that modern cards have about 30 - 70 ECUs, but I couldn't find good sources for that. Do you have (citable) sources for where ECUs in modern cars are, ...
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47 views

Dealer can't program new ECU for 2001 Mercury Cougar because of transmission type

I brought the original ECM in to order a replacement, put it in myself, and then towed the car to Ford. Now they are saying they can't program it because the computer is for a manual and my car is an ...
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1answer
113 views

Reprogramming a Magneti Marelli Microplex MED604C

Im interested in reprogramming a Magneti Marelli Microplex MED604C ecu for the ignition of a uno turbo, but I can't seem to find any documentation for this? I'm new to ecu remapping, and my ...
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534 views

Honda Civic 2000 DX, Check Engine Light Becomes On but Does Not Give OBD Code

On my Honda Civic DX 2000, the Check Engine Light (CEL) has been on for a while, so I brought the car to AutoZone to have the OBD code read, but I was told that no code is stored in the computer. ...
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122 views

1995 VM Jetta/Vento - ECU pinout for my car

I own a 95 Vento GL (Jetta for the american market), with an 1.8 8v, 90hp ADD model engine. The ECU for this model is marked with part number 037 906 021A. I have checked with VAG-COM software and it ...
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83 views

Why don't thermostats have a sensor?

One of the more common reasons of overheating is a stuck thermostat. One of the most common reasons for blown head gaskets is overheating. One of the most expensive vehicle repair procedures is head ...
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133 views

ECU Diagnostic Port cut off and Check Engine Light disabled

I bought a used 92 Integra ZXi recently. I had starting issues so I took it to a mechanic. He found that the check engine light is disabled and diagnostic port from the ECU has been cut off. A very ...
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72 views

Are there plug-n-play ECUs?

I was just curious if there is such a thing as aftermarket plug-n-play ECUs that are compatible with a vehicle (have all the features the OEM ECU does) but also have some extra ones, such as maybe ...
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208 views

Do I need to reprogram ECU when adding custom Air filter

I was thinking of replacing the air filter of a bike into a custom free flow filter. I understand that I have to mod the exhaust to free flow as well to accompany the increase in exhaust due to the ...
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192 views

A most intriguing cold-start misfire mystery

I'm trying to help a friend out with a CEL on his 2009 Merc GLK 280. Hooked it up to an OBD2 reader and retrieved a single code: P0300 - 'Random/Multiple Cylinder Misfire Detected', via the 'OBD ...
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339 views

Will vtec engage without a factory released VTEC ECU when swapping to VTEC engine?

I replaced my honda civic d15z4 engine with a d16A. Apparently, VTEC engages at 5500rpm on these engines. My car is still practically standard, I'm not sure if it does switch over, if it does, the ...
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'93 Cavalier ECU issue

I have an old cavalier that loses power to the ECU randomly. It can take many attempts to start again. I do not lose battery power to the lights or stereo. If I flick the keys to the on position ...
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813 views

2001 Toyota 4Runner - ECU Drive Cycle Reset

After changing sensors that were bad on a Toyota 4Runner an emmissions technician stated that the vehicle needed to be driven "for awhile" before the "drive cycle" would reset the ECU to the new ...
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229 views

2005 Toyota Avalon how to reactivate vehicle's ECU

2005 Toyota Avalon FOB stopped working, have a replacement. Now believe accidentally deactivated vehicle's ECU by turning ignition on/off 5 times during process of adding new FOB. So now, how can I ...
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85 views

Is it common for ECU's to maintain individual limit maps for each knock sensor?

Preamble I'm in the process of interpreting my BMW M5's ECU binary with the aid of some nifty scripting and rather informative forum posts. One of the things I've found is that there are knock limit ...
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1answer
26 views

Dash compatibility and the ECU

I have a Citroen C1 and it's a very basic model. It doesn't have a rev counter but I can add one because it has the cable and plug for it already exists, it's just not plugged into a rev counter. What ...
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154 views

How are fuel injectors controlled?

I took the fuel injectors off of a wrecked Volvo 850 GLT 1996. I was testing them to see if they still worked by simply supplying voltage to them, and they do. I noticed that when I increase or ...
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1answer
219 views

Do I need a new ECU after replacing the transmission?

I replaced the transmission in my 2002 Lexus RX 300 about one month ago. The mechanics reprogrammed my ECU immediately, and they advised me to replace my ECU with a new one, because with the old ECU I ...
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Mazda Lantis 323 1997: OBDI or OBDII?

I'm still trying to figure out if my 1997 Mazda Lantis 323 GLX 1.8L DHOC Manual is OBD 1 or 2. It's supposedly similar to the Protege of the same year and it says on autozone: In order to ...
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176 views

Mazda 323: Does the EMU / ECU learn?

I have a Manual 97 Mazda Lantis 323 1.8L DOHC 16 Valve BP and was wondering if the EMU / ECU on it learns? Could unplugging the battery to reset it help some of my problems with erratic idle? I found ...
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145 views

Scanning CANBUS [duplicate]

I am in search for a method of scanning the CAN on my car using a cheap ELM327 chip. I can query the ECU (made by Denso) without issue, however when I attempt to set the ELM327 scanner into ...
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435 views

Fiat 500 Airbag Sensor

My Fiat 500, 2008, 1.2 Pop, 51Kw has had its front left side somewhat crushed. The body has been fixed for the most part, but the electrician/mechanic tells us he cannot turn on the vehicle in order ...
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271 views

Error Message from OBD-II (7F 01 11)

I have been extracting OBD-II DATA from UART board (ELM327) on my TOYOTA INNOVA. It responded correctly few weeks before and gave all supported sensor values. But now, for every response, ECU responds ...
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Why do we need make-specific cables to read car ECUs?

I find it bizarre that the automotive industry has standardized the use of the OBDII protocol, yet most cars require make-specific cables in order to access the complete set of diagnostics and ...
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368 views

2005 Nissan Sentra - Pressing gas pedal has no effect - vent control valve

My car (2005 Nissan Sentra) had a problem for a while: gas spills out when pumping. I was lazy and did nothing about it. After a month or so, the car started to fail. At first it was only hiccups, but ...