On-Board Diagnostics-II (OBD-II). Questions usually involve scan tools, their use and their compatibility, as well as how to interpret Diagnostic Trouble Codes (DTCs).

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20
votes
2answers
912 views

Difference between OBDII and CAN

What is CAN (controller area network)? What are the differences between an OBD-II protocol and a CAN setup?` How do I use an OBD-II scanner on a vehicle with CAN?
18
votes
3answers
617 views

What are good features to look for in an OBD-II reader

I recently took my car in for the engine light. It turned out to be a minor problem (crack in gas cap let water in). It would be nice to have a low-cost OBD-II reader to be able to find out for ...
17
votes
3answers
6k views

Can a vehicle be harmed with bad inputs via an OBD-2 port?

I bought a cheap (sub $10) ELM 327 Bluetooth clone OBD-2 diagnostic adapter on a local "ebay-style" market where the seller specializes in car diagnostics and has several thousand positive reviews ...
15
votes
1answer
2k views

How do I find the correct pins in a CAN-BUS connector?

This question might be too technical for this forum, but I'll give it a go. I have a 2012 BMW R1200R motorcycle with CAN-BUS. I'd like to make an Arduino interface to the connector on the bike, but I ...
14
votes
3answers
93k views

What iPhone/iPad app works best with ELM327 Bluetooth OBD-II reader?

I've found a number of apps for the iPhone/iPad that connect to ODB-II readers via WiFi, but unfortunately that means that it disables 3G and all the benefits of having a 3G device built into my dash. ...
14
votes
3answers
987 views

What to know before buying and OBD-II reader

I read the features to look for in an OBD-II reader, but I am curious if getting one is the right move. I'm just planning to get a cheap one, which is proving to be interesting shopping local. What I ...
12
votes
2answers
442 views

What is the motorcycle equivalent of OBD-II?

I once met an OBD-II expert while traveling and asked him if motorcycles (especially the fuel-injected ones) employ a similar protocol. He said that the use of such a protocol is not as widespread ...
11
votes
1answer
85 views

Are there any plans to update OBD-II?

OBD-II is ancient It predates the Porsche 911 GT1, Windows 95 and implementation of the Schengen Agreement. I would have thought that SAE would be working to add more diagnostic coverage for ...
10
votes
2answers
1k views

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 ...
10
votes
1answer
78 views

Computing Wheel Torque From Engine Torque

It seems possible to obtain engine torque and RPM from a truck CAN bus. I'd like to estimate tractive force at the wheels given these two values. How should I go about computing torque at the wheels? ...
10
votes
1answer
408 views

How to detect engine/ignition (on/off) status using OBD2?

My device needs to know when a car engine/ignition is started and stopped. Is it possible to get that status using OBD2? If yes, which PID will give me that information? Do I need to write any ...
9
votes
3answers
205k views

What is the pin or keycode for ELM327 bluetooth OBDII adapter?

The infamous ELM327 OBDII device came without any paper, just a crappy CD with no document related to the device (only some software and drivers thrown on the CD almost randomly). I tried the ...
9
votes
4answers
167 views

Disabling OBD2-Interface in a car

If a car-thief wants to steal a modern car, he often uses the OBD2 (On Board diagnosis) to "hack" the car. Simplified: He achieves this by plugging his "hacking device" in the port, which aquieres ...
9
votes
2answers
113 views

Received frames from vehicles with multiple ECU chips

I'm not generally a 'car person', so hopefully I can explain this well enough to get some help here: When sending messages to an OBD-II device, I receive one response in most cars I've tested. ...
8
votes
4answers
543 views

Is control module voltage and battery voltage the same?

Is the Control Module Voltage (from OBD Mode 01 PID 42) and battery voltage the same? If not, what is the relation between them? Why is the max value of Control Module Voltage (from OBD Mode 01 PID ...
7
votes
2answers
7k views

Should I replace my own oxygen sensor if i have a Check Engine Light and Code P2195?

My 2003 focus lx 2.0L L4 SOHC ~18,000 miles has had the engine light so i went to autozone to read the code. Autozone obd2 printout says "P2195 lack of heated oxygen sensor- Bank 1 Sensor 1 HO2S11 ...
7
votes
1answer
216 views

Is it possible to auto close the power window of a car using OBD and CAN bus?

I am not an electrical or automobile engineer, so pardon my ignorance. I found this product in the market to auto close power windows for certain brands. How can we send signals to the CAN bus using ...
7
votes
5answers
1k views

Are there any OBD II converters on the market?

I know there are tons of readers and software on the market, but what I really need is something to convert signals of my1970s sensors (fuel level, speed, coolant temp, etc) to OBD compliant signals. ...
7
votes
1answer
169 views

ATMA on OBDII not Working

I have successfully connected a terminal android app to the obd port of my car. And tried dry run of many at commands, many are working as expected. But ATMA (AT command to Monitor All) is not ...
7
votes
1answer
51 views

Erratic single fault code: P0420, P0440, P0446. Normal variance, or indicative of something deeper?

Working on diagnosing an evap/emission/fuel system problem on my Toyota 2003 Corolla. More on that in this question. On 3/2, I saw a mechanic use his handheld OBD to read a code P0420. On 3/12, ...
7
votes
1answer
5k views

Can I use an OBD2 Scan Tool on older GM vehicle?

I can get an adapter that connects my OBD2 scan tool to my 12 pin GM scan tool connection. But will the tool be able to read the codes and tell me anything useful? Or do I need to get a scan tool that ...
7
votes
3answers
571 views

Calculating MPG from MAP sensor (or converting MAP data to MAF data)

My 2002 Honda Accord V6 has a Manifold Absolute Pressure sensor (MAP). I understand that this sensor gives out information in pressure units (psi or equivalent). After doing a bit of research, I ...
6
votes
4answers
5k views

Controlling door locks via CAN bus

I'm trying to figure out how to lock and unlock the doors of a 2010 Toyota RAV4 using the CAN bus via the OBD-II port. I have a microcontroller attached via an CAN controller and a CAN receiver, and ...
6
votes
2answers
57 views

Calculate amount of fuel injected

How do I calculate the amount of fuel injected (both gasoline and diesel cars). I want an instantaneous value. http://www.rceng.com/technical.aspx Websites like these ask for 'Desired Crankshaft ...
6
votes
4answers
4k views

shop can't connect to onboard diagnostic system?

I've recently moved to California and am trying to get my car registered; they require a smog check (which is possibly actually more of an inspection than the name implies?). I went by a very basic ...
6
votes
1answer
37 views

On-Board Diagnostics (OBD) Readiness Monitors

I would like to know how does apps like Torque calculate if my car (Hyundai i10 Era) is 'Not ready' yet? What are the factors (complete list) do one checks to decide? Is there any formula to calculate ...
6
votes
1answer
311 views

OBD2 and CAN-bus

Do all vehicles with OBD2 have a CAN-bus? Otherwise, what are the alternative buses used? Are there special versions of the buses for trucks and school-buses than for cars/suv/vans?
6
votes
1answer
2k views

What is supposed to happen when my Subaru's test mode connector is hooked up?

There's an electrical connector under the dash of my 2000 Subaru Forester that is apparently instrumental in the diagnosis of some OBD-II trouble codes. It's a pair of bladed terminals like any other ...
6
votes
1answer
125 views

ODIS 5.0.6 diagnostic tool : how can I remove an option from a transformed vehicle?

We have a transformed car, a Bentley, which no longer has a motorized sunroof. The blind has also gone. However the car diagnostics exhibits a fault on the related, non-present devices and motors. We ...
6
votes
1answer
442 views

Does OBD II explicitly or implicitly include forward/reverse information?

From my understanding, OBD II does not directly tell if a car is in forward or reverse gear. I wonder what the best way to derive such information from OBD data if there is any. Following the ...
6
votes
1answer
49 views
+50

How do I get to see my Mode 06 in OBDii

Mode 06 in OBD2 is good to get an insight of what faults the car might encounter in the future. But I am unable to find out what command should I send to get Mode 06 data. It has TID$01 CID$01, so how ...
5
votes
2answers
555 views

Writing CAN Messages

I want to know what should I write with the CAN ID to send it to ECU. I am using ELM327 and Raspberry Pi with all connections to OBD-II. Initially for sending general PIDs to the ECU through ELM327 ...
5
votes
2answers
128 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 ...
5
votes
3answers
70 views

Mode 02 - Freeze frame data use

I got some data on sending 0202 command (Mode $02, PID 02). It is the freeze frame data. I don't understand why does anyone need the data? Do anyone (including mechanics) ever open Freeze frame data? ...
5
votes
1answer
141 views

Difference between fuel pressure and fuel rail pressure

In OBD PID wiki page, there are 2 PIDs listed: Fuel pressure and Fuel rail pressure. Are both of them the same? Can someone please give an elaborate explanation of it - What exactly are they ...
5
votes
2answers
909 views

Reading OBD2 too fast

I'm writing a software to make a telemetry application for my 2001 VW Golf mk4 reading parameters from OBD2 using an ELM327 compatible cable. I succeeded so far. The problem that I have now, is that ...
5
votes
2answers
59 views

Is it possible to access multiple CAN buses through the OBD-II port?

As usual I apologize if this has been asked and answered somewhere. I try to only ask questions if I can't find an answer or a satisfactory answer. From my understanding the OBD-II port on vehicles ...
5
votes
2answers
351 views

What is the point of a vacuum pump with a fuel injection engine?

I recently got an OBD-II dongle with the Torque Android app, which allows me to read the computer's output in real time. The app will let me drag and drop different gauges on my screen, which works ...
5
votes
3answers
11k views

OBD-II reader/scan tool that can also diagnose air bag light

Is there an OBD-II reader/scan tool that can also diagnose air bag warning light? My 2004 Honda Element EX has a red air bag warning light that recently has turned on. The nearest Honda dealer wants ...
5
votes
1answer
120 views

Is Torque App reliable to read O2 sensor data?

My 2006 Toyota Prius is throwing code P0420 and I used a cheap OBD-II reader with Torque App on Android to check if my O2 sensors are working or not. I tried the maintenance mode to just run the ...
5
votes
1answer
82 views

2005 hyundai elantra error code p0501

So my 05 Hyundai Elantra has the check engine light on. I took it to the store & had them put the code reader on & it comes up with p0501 vehicle speed sensor performance. My question. . is ...
5
votes
1answer
877 views

OBD 2 Fuel reading says No Data

I wanted to read fuel level from the car and display it on my application. The communication was established using the ELM327 Bluetooth interface dongle. The ELM module replies NO DATA for the code ...
4
votes
2answers
181 views

Any open-source OBD scanner analysis tools?

I've been having some weird problems with my '06 Pontiac G6, and finally broke down and bought a Bosch code scanner to see if the DTCs could tell me anything... they didn't. This scanner has the ...
4
votes
5answers
7k views

Is it worth getting an OBD2 scanning tool?

I have a Opel Corsa 1999 B type. It is giving me problems now. I have read a little bit about OBD2 scanning tools. But don't know if one could help me, or that I am maybe hoping for too much. I ...
4
votes
1answer
105 views

Nitro OBD2 SCAM OR WORK?

I was looking into general car stuff like storage and lights the general stuff. I ran into a device called a "nitro OBD2" they have one to save fuel one to generate more power and stuff. Looking into ...
4
votes
2answers
2k views

OBD II power when key not in ignition

I can't get to the OBD connector on my car at the moment. As far as I know the OBD II voltage is active even when the key is in lock. Can anyone confirm this? edit : It's for a product that ...
4
votes
2answers
191 views

Replacing Cam Position Sensor; any gotchas?

I have a 2007 Nissan Murano. My Check Engine light is telling me that the cam position sensor (bank 1) is bad. I've located the sensors, and they are both readily available and easy to get to. Is ...
4
votes
1answer
1k views

How much battery does an obd bluetooth reader suck?

I'm planning on using an obd bluetooth reader on my car and leaving it plugged in to use apps like dash and torque. It's a daily driver so I'm not that scared of depleting the car's battery, but I ...
4
votes
1answer
1k views

Subaru Forester OBD Scan Codes “P0130” and “P0130 P”

My 2002 Forester Check Engine light is on. I connected an Autel MaxiScan MS300 OBD-II scan tool and got indication for two codes. Browsing through the codes, it reads P0130 and P0130 P. The first one ...
4
votes
1answer
30 views

What does it mean when the ELM327 OBD2-reader gives two lines of info for 0100 request?

I have an ELM327-based OBD2 reader that I can issue commands to when connected to a car. I'm running this on a 2015 Acura RDX. When I issue the request 0100 to get supported mode 1 PIDs, I get the ...