OBDII Communication Issues On Start

[Chuck Gillming]

1999 Sport 4.0 Manual - Trying to read OBD II live data, scanner communicates with PCM “live data” with ignition on and engine off. As soon as I start it the communications fail and I receive a “function not supported” message. Anyone run into this issue or have any suggestions on the cause? BTW, its running very poorly but it's not showing codes.

 

[macleanflood]

What are you using to read the data? Bluetooth reader and Torque Lite?

-Mac

 

[Chuck Gillming]

What are you using to read the data? Bluetooth reader and Torque Lite?

-Mac

Was using Accel AD 310 with issue noted above. Seemed to read if I plugged it in while it running but it's running so bad I have to feather it frequently and not sure if I was getting a complete set of info. Now have a Veepeak Bluetooth scanner and Torque Pro. It seems to be reading OK (I think - cuz I'm just getting used to it). Readings coming out with hexadecimal titles. WTF?, looking into that. Any advice on using the Veepeak? Thanks.

 

[mrblaine]

1999 Sport 4.0 Manual - Trying to read OBD II live data, scanner communicates with PCM “live data” with ignition on and engine off. As soon as I start it the communications fail and I receive a “function not supported” message. Anyone run into this issue or have any suggestions on the cause? BTW, its running very poorly but it's not showing codes.

Dig around and see if you have any melted harness any place. When we run into that, the typical cause is the 5 volt sensor reference is shorted to ground via a melted harness some place and is pulling the PCM down.

 

[Chuck Gillming]

Dig around and see if you have any melted harness any place. When we run into that, the typical cause is the 5 volt sensor reference is shorted to ground via a melted harness some place and is pulling the PCM down.

Can I confirm short at OBD port or elsewhere with an ohmmeter before I go digging?

 

[macleanflood]

I'd download and check the FSM for your Jeep. You know you have power... Bluetooth reader wouldn't work without it.

-Mac

 

[mrblaine]

Can I confirm short at OBD port or elsewhere with an ohmmeter before I go digging?

Depends on where the short is.