Motor Vehicle Maintenance and Repair Stack Exchange
Motor Vehicle Maintenance and 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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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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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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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 do I send the command? 060101 or 0601? Please…
Soumya Sen
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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) as 65.535 V, when the battery voltage can at…
Soumya Sen
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OBDII across the world?

Is OBDII consistent across the world? Any vehicle sold in North America particularly in the United States must conform exactly to all OBDII rules. What about vehicles that are sold in the US but also sold abroad? For instance imports such as BMW…
vini_i
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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 discussion in this post, specifically I would like to…
sma
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Would OBD-II devices drain the battery when used 24/7?

There are many OBD-II devices out there that can scan and/or monitor real-time data about your car. Most of these devices are readable via USB or Bluetooth. Either USB or Bluetooth, both require some amount of power. Will these devices drain the…
Abel Melquiades Callejo
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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 out great. However, there is a gauge for vacuum…
Rubber Duck
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How can I access the output of my backup camera?

My 2016 Subaru Forester has a backup camera. First I've ever had, and very neat. Of course, it engages the screen when I put the car in reverse, and shuts off in other gears. I've been reading about the Media-oriented system transport, (MOST)…
Tupelo Thistlehead
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OBD2 Mode 9 Calibration ID and Numbers

What is the actual use of the OBD2 Mode 9 Calibration ID (0904) and Calibration Numbers (0906)? Are they constant or do they change? If so, under which circumstances? I have read the standard, but I'm afraid besides explaining the decoding, it's not…
DrMickeyLauer
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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 them more I see many mixed reviews from general…
DnrDevil
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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 012F\r. Is there any other way to calculate or get…
Strikers
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How to view error codes on a speedometer with no OBD reader?

I have a 2000 Dodge Neon and don't have a real OBD reader yet. The other day I started to turn my car on and, before I got to the ignition the speedometer came on with a "p" and a "1684" (the check engine light has been on for a while). I tried to…
jtpereyda
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