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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22
votes
4answers
9k 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 (...
21
votes
2answers
1k 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?
19
votes
3answers
656 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 ...
15
votes
3answers
96k 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. ...
15
votes
3answers
1k 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 ...
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 ...
13
votes
3answers
2k 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
100 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
672 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 car-...
10
votes
1answer
124 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? ...
9
votes
3answers
220k 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
529 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
210 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
986 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 42)...
8
votes
1answer
468 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 ...
8
votes
1answer
7k 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 ...
8
votes
2answers
110 views

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 ...
7
votes
2answers
8k 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
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
333 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
106 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
3answers
758 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
3answers
250 views

Tapping into the on-board computer

I'm thinking of replacing my car's radio panel with a custom built Raspberry Pi device, something like this device. However, it's usefulness would be much larger, if I could get information from the ...
6
votes
4answers
6k 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 I'...
6
votes
2answers
77 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 Power'...
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
38 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
31k views

'Check Engine' code P0171 System Too Lean - Is it safe to drive?

My 2003 Toyota Corolla's Check Engine Light came on. I read the codes using an OBD code reader and got P0171 - System Too Lean (Bank 1) and P0133 - 02 Circuit Slow Response (Bank 1, Sensor 1). The ...
6
votes
1answer
337 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
3k 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
140 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
547 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 ...
5
votes
3answers
10k views

Can OBD-II be used to control the vehicle?

Is the OBD-II port in vehicles only used for reading diagnostic codes or is there some functionality that allows the vehicle (eg. engine revving) to be controlled through OBD-II? Thanks.
5
votes
3answers
136 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
2answers
610 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
152 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
1answer
371 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
3k 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 ...
5
votes
2answers
973 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
115 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
386 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
12k 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
2answers
51 views

1989 Chevy Scottsdale 2500 HD 5.7 liter 350

I have just finished a body off restoration of my 1989 Chevrolet Scottsdale 2500 HD. My question, is there an OBDI or OBDII or do I need a adapter to scan it? Even if I rebuilt the engine and ...
5
votes
1answer
66 views

What's the Difference Between OBDII adapters and Toyota Mini VCI?

I've been researching Toyota diagnostic connectors, and ran across something called a Mini VCI adaptor meant for use with Toyota's TechStream software. The physical interface looks like a standard ...
5
votes
1answer
394 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
111 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
3answers
122 views

Can the throttle position be high during idle

I used an OBD to get data from one of my friend's car - Volkswagen Polo 1.5L Diesel. But the car was idling at around 900 rpm, while the throttle position I got was around 22%. How is it possible? As ...
5
votes
1answer
1k 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 ...
5
votes
1answer
60 views

DIY OBD II “Memory saver”

Since I had a need for a "memory saver" while changing a battery on a 05' S500 I decided that instead of borrowing one from a friend all the time, I will make my own.. Now isn't it just a power supply ...