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40

Ok, before I will answer your specific questions, let's do some introduction on bus systems. It could be that you know parts of these things, but I will start here as people with little or no IT or electronics knowledge should be able to understand this as well. Bus Systems In electronic systems signals are sent from one chip to another using wires (let's ...


23

In most cases, unless things have been cleared, there's a good chance that if there was an issue previously, the codes will still be present in the ECU. Some codes are permanent (well, semi-quasi-permanent ... there are ways to get rid of them, but not for the "average" person), so will stay in the ECU. If a problem is intermittent it could cause ...


20

Ultimately the answer is yes you can. To qualify this answer, though, you can only control some things, but not all things, then only on some vehicles. You can do simple things through the port, such as turn the A/C pump on, or any other thing which is controlled by the computer (PCM). As an extension, I'm sure you could rev the engine using the same methods ...


20

It is highly probable that the reason your car was reluctant to start was that the time you were running diagnostics had sapped some of the charge from the battery. The battery on the car will not charge unless the engine is running. It is unlikely that this device would harm your vehicle but it is theoretically (and practically) possible to do temporary ...


12

Maybe not answering your question completely, but: some people doubt how the OBD II connector is connected to power. The specification (SAE J1962 specification) of the connector is quite clear on this: 5.3.9 (...) Vehicle connector terminal 16 is designated Unswitched Vehicle Battery Positive and must be implemented in the vehicle connector. This terminal ...


12

Sometimes second-hand car sellers turn off or remove warning lights from dashboard in order to hide some problems, rather than spending money to fix them. Therefore, an OBDII diagnostic made by a good mechanic can save you money either by not buying the vehicle or by negotiating a better price from the seller.


11

You're glossing over how the hack actually happens. The hack involves erasing the old keys and then reprogramming a new key to the vehicle. If the car uses a smart key then you're in right away. If the car has a physical key, then having the correct cut of key is also required. Cars also fall into two categories. The first is the real expensive cars that ...


11

The computers in a car are constantly monitoring the operating conditions and sensors that are in the car. When a test fails or something goes out of a pre specified range a DTC is set. The biggest misconception about a DTC is that it tells you what to replace, it does not. A DTC tells you what test failed or what parameter went out of range. This ...


11

There is a place where this reader can be useful. Know the age of the car, and your state regulations, to find out how many 'Not Ready' monitors are allowed before the car will fail emissions. If there is an Engine light turned on on the dashboard, you won't pass emissions - so walk away. If the seller says "It's an easy fix", ask them why they didn't do ...


10

Looks like the issue is with the incoming signal. Unless your vehicle comes equipped with a flux capacitor, 65 V across battery is a bit too much. Even heavy trucks don't run that voltage to my knowledge. 65535 is the max unsigned 16-bit integer. Looking at the OBD-II wiki page it looks like the formula used by the OBD-II PID as per SAE J1979 is: ( A * ...


10

Some motorcycles have a CAN BUS, some don't The OBDII connector type is simply a standard instituted by the SAE (Society of Automotive Engineers). In 1996 the US government mandated that all cars sold in the United States conform to the SAE OBDII standards. They didn't specify motorcycles. As result, a myriad of on-board diagnostic methods were ...


10

On a car with fuel injection there can be two fuel pumps, one high-pressure and one low-pressure. The low-pressure pump moves the gas from the tank up to the high pressure pump. The high pressure pump then raises the pressure to a level that will be useful to the injectors. The two PIDs reflect those two different systems. PID Description Min ...


10

It really depends on the implementation of OBD2. What my 1997 Subaru logs (virtually nothing) compared to a 2015 Chevy Cruise are entirely different things. However, in most cases, a Diagnostic Trouble Code (DTC) is logged with a freeze frame, which is a complete store of all Parameter ID's (PIDS). These parameters cover everything from RPM, vehicle speed,...


10

If the engine isn't running, then they surely will. I have an ELM 327 (Bluetooth) device which plugs into the OBDII port. Even when the vehicle is turned off, the device is active. Before I realized this, I had left it plugged into my car, came out the next day and the battery was dead. Inside the OBDII port, the power lead there is always on and gives ...


9

I am not sure of your exact solution, but Brian Blum of Texas Instruments says the amperage draw depends on what state the device is in, of which there are seven states. According to the document in the link, it draws as follows: State 1 (wake-up) - 6.1mA State 2 (pre-processing) - 8.1 mA State 3 (pre-RX) - 12.3 mA State 4 (RX) - 22.3 mA State 5 (Rx-to-Tx) -...


9

To my knowledge there is no way a scanner can cause issues with your computer electronics. This device is a read only device. It doesn't change anything in your computer. It does, however, communicate with the computer. Through this communication it can give the computer commands, such as to clear the codes. This doesn't write anything to the computer, but ...


9

Everything depends on if the manufacturer multiplexed the windows or not. For example, General Motors tends to multiplex their windows. This means that every door has a module inside it. The module controls the window, door lock, power mirror, etc... and takes inputs from door lock and window switches. The only thing to pass through the door jam is power ...


9

Everything depends on exactly what your looking for. If engine running/not running is sufficient then check the RPM. If RPM is non zero, the engine is running. If the RPM is zero or no communication then the engine is not running. This can be easily done in the OBD stream. If you want anything more than that you need manufacturer specific and then not ...


9

OBD II is a US government mandated diagnostic interface. This interface is guaranteed to provide a specific set of information including but not limited to engine computer data and engine computer trouble codes. When OBD II was rolled out the US government did not force the manufacturers to also standardize the communication interface to the engine ...


9

try this AT H1 this will turn on headers, then do 0100 you will get something like 7E8 06 41 00 BE 3E A8 13 7E9 06 41 00 98 18 80 13 which says you are getting results from ECUs 7E8 (engine) and 7E9 (transmission)if you are running on an 11bit CAN. If you get 18 DA F1 18 06 41 00 88 18 00 13 18 DA F1 10 06 41 00 BE 5F A8 13 then its results from ...


8

Did you set the protocol for the chip to monitor on? e.g. ATSP5 for KWP-2000 or ATSP0 for "best guess". What about checking the headers as well - ATH1? I use the following string of commands to monitor my full KWP bus, which is obviously different from CAN, but is similar enough that it might be of use: ATI -- check connection from app to scan tool ATH1 --...


8

The ELM327 is (almost?) as powerful as any other diagnostics solution. That's simply because it only translates the low level OBD protocols to some other format. Bluetooth connections on mobile phones seem to be flaky on many devices. Usually, this shows as established connections suddenly failing during transfer. Restarting the app, and/or turning the phone'...


8

You are over thinking things, just connect your devices (OBD & Pi) to a good chassis ground: The difference between chassis and signal ground is: Chassis Ground Pin 4: Is exactly that, connected directly to the chassis or battery negative terminal. Signal Ground Pin 5: Is designed to provide a 'clean' ground isolated from any noise from devices such ...


8

He can also look at fuel trims and other sensors performance. Some conditions on an engine may be efficient enough to keep the engine light off, but not in an ideal range.


7

There's a lot of work going on in this space, so the answer is "Yes, Of course!" Here is a Python project: http://www.obdtester.com/pyobd This looks like an interesting way to get data from the car, but doesn't seem to really be about trouble codes or diagnostics: http://openxcplatform.com/getting-started/index.html This looks very outdated, but maybe ...


7

Pin 16 on the ODB-II connector is specified as "Battery Power" or "Battery Positive". There will always be 12v power between pin 4 and 16. Note that pin 5 has "ground" in the description, but that is just for the communication signalling and not for power. The connector will always have power on these two pins regardless of the key position, and when you ...


7

Modern gasoline engines have sensors to measure the amount of air that enters the engine. The ECU then injects fuel to give the correct mixture to get the most efficient burn. A dirty air filter will first show itself by limiting the flow of air at high throttle positions. Rather than causing a rich mixture however, the ECU will see the low air flow and ...


7

The short answer is: no - not without the manufacturer's diagnostic tools. The long answer is: maybe. Modern cars have most (if not all) exterior and interior lights controlled by the body control module (BCM). Most (if not all) switches are connected to the BCM as well. This provides a lot of flexibility. A prime example is if you leave your headlights ...


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