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obdiiMasterMind · 12-21-2006, 04:51 PM

Quote: Originally Posted by plisskin

I am trying to build my own OBD-II reader using a PIC. So far I am able to connect to ISO9141-2 and J1850 VPW but am having some trouble with J1850 PWM.

When I send the J1850 PWM message, I cannot get an answer. I have put a scope on Pin 2 and Pin 10 and see the message go out and also a 1 byte IFR being returned from the vehicle approx. 40 us after my message. But no other message is returned from the vehicle.

For example, I transmit 0x61 0x6a 0xf1 0x01 0x00 0x0a which is supposed to read the supported PIDs of the vehicle. All I get back is a 1 byte IFR of 0x1f.

Does anybody know if I am supposed to transmit again after the 1 byte IFR or am I doing something else wrong?

So far, I am using only information that I have found on the internet, such as obddiagnostics.com

Thanks for your help.

What "pic" are you referring too? i would like you're knowledge on the j1850 protocol if you have any. are you willing to share you're knowledge? is the pic you're programming something you bought, or something you actually programmed to logg and send data? if you programmed it with assembly etc,, we would defently need to share knowledge.

12-21-2006, 04:51 PM	#5
obdiiMasterMind Newbie Join Date: Dec 2006 Posts: 5	Quote: Originally Posted by plisskin I am trying to build my own OBD-II reader using a PIC. So far I am able to connect to ISO9141-2 and J1850 VPW but am having some trouble with J1850 PWM. When I send the J1850 PWM message, I cannot get an answer. I have put a scope on Pin 2 and Pin 10 and see the message go out and also a 1 byte IFR being returned from the vehicle approx. 40 us after my message. But no other message is returned from the vehicle. For example, I transmit 0x61 0x6a 0xf1 0x01 0x00 0x0a which is supposed to read the supported PIDs of the vehicle. All I get back is a 1 byte IFR of 0x1f. Does anybody know if I am supposed to transmit again after the 1 byte IFR or am I doing something else wrong? So far, I am using only information that I have found on the internet, such as obddiagnostics.com Thanks for your help. What "pic" are you referring too? i would like you're knowledge on the j1850 protocol if you have any. are you willing to share you're knowledge? is the pic you're programming something you bought, or something you actually programmed to logg and send data? if you programmed it with assembly etc,, we would defently need to share knowledge.