Motor Vehicle Maintenance & Repair Stack Exchange
Motor Vehicle Maintenance & Repair Stack Exchange

Questions tagged [obd-ii]

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).

On-Board Diagnostics-II (OBD-II)

On-Board Diagnostics-II is a standard for vehicle self-diagnostic data capabilities as well as real-time data reporting capabilities.

Protocols

The OBD-II standard allows for five different signalling (or data) protocols to be transmitted through the OBD-II interface. These are:

  • SAE J1850
  • PWM SAE J1850
  • VPW ISO 9141-2
  • ISO 14230 KWP2000
  • ISO 15765 CAN

OBD-II Scan Tools

Most modern scan tools are capable of reading the 5 different data protocols. Most are capable of resetting/clearing fault codes while more advanced tools are capable of setting ECU parameters, controlling other on board units such as ABS and Air Bags as well as real time monitoring and data logging of various engine parameters.

Further Reading

  • A list of PIDs can be found on Wikipedia.
  • A list of trouble codes can be found here.
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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?
Shobin P
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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 (read: I guess this seller would not provide…
Kozuch
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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 myself and either go to service immediately or delay…
Brian Carlton
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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.
Bert Wagner
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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 following codes without being able to pair it with my HTC…
sorin
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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. I can't seem to find any apps that work via…
Chase Florell
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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 but when they use it, it isn't OBD-II. I cannot…
Zaid
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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 don't know the pin definitions... Do anyone know…
Eric Fossum
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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 expect to happen is I will read the code, go to…
Jim McKeeth
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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 utilities. A few examples: VWs require a VAG-COM…
Zaid
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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-specific logic in my device to support this feature?
rp1980
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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. However, with cars that apparently have more than one…
Rein
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What is the point of performing an OBD2 diagnostic scan if there is no malfunction indicator?

Where I live, it is common for car mechanics to help their customers who are planning to purchase a new used car by performing an OBD2 diagnostic test on the car in question, even if there are no dashboard warning lights. What is the point of this?…
hb20007
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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've written some firmware to capture and replay…
Isvara
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Do fault codes get recorded with a time stamp into a log with a history of DTCs?

Just scanned my vehicle for the first time to check out the code for a Check Engine Light. I grew curious if these fault codes get logged somewhere with a date and time stamp of some kind at the time they were thrown. I'm imagining some design…
jxramos
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