Create an OBD Trouble Code?

**god_of_cpu** · 05-26-2004, 11:57 AM

I just finished building my OBD reader program for the ELM chip and I now need to test the Mode 3 and 4 functions for it that query and reset trouble codes. Anyone know of the easiest way to create a trouble code in my car so I can test reading and resetting the trouble codes.

Preferably something easy to do that won't damage anything?

**Curiosity** · 05-26-2004, 12:07 PM

I was thinking about doing that too, and would assume you could just unplug the mass air flow sensor and turn the key on without cranking the engine. You could probably do that with temp sensors as well. Anyone know for sure?

**buterbn** · 05-26-2004, 12:28 PM

I know on a lot of new cars that if you dont tighten the gas cap all the way you will get a code. You might want to try that

**god_of_cpu** · 05-26-2004, 12:55 PM

Thanks, for your replies.

Looks like disconnecting the MAF is the way to go.
http://g35driver.com/forums/showflat...sed&sb=5&part=

**Zip-Lock** · 05-27-2004, 07:10 AM

The air intake temperature sensor is an easy one too.

**Zip-Lock** · 05-27-2004, 07:10 AM

You can also take off the gas cap, don't even have to open the hood for that one.

**DavidL** · 05-27-2004, 09:41 AM

The gas cap deal isn't instant. There is some tolerance to the ECU reacting.
another good bet is the coolant temp sensor. This will throw the vehicle into "limp mode" and launch a DTC (diagnostic trouble code). Of course, you will need to clear the code once you are done testing and plug the sensor back in or you will have a sick running car for a while.

**god_of_cpu** · 05-28-2004, 09:47 AM

Disconnecting the MAF worked like a charm, took about 2 seconds to do and immediatly caused the car to generate a trouble code. Took me about another hour to figure out why I couldn't read it... Turns out you have to send a mode 1 pid 1 message first to read the number of codes before you can send a mode 3 request, otherwise the mode 3 request will respond that the mode 3 request was successful, but won't return the trouble code.

**muldrick** · 06-23-2004, 04:43 PM

Originally Posted by god_of_cpu

I just finished building my OBD reader program for the ELM chip and I now need to test the Mode 3 and 4 functions for it that query and reset trouble codes. Anyone know of the easiest way to create a trouble code in my car so I can test reading and resetting the trouble codes.

Preferably something easy to do that won't damage anything?

I hope you can clear it.
Disconnecting the battery may not clear it.