OBD II Protocols and tools

[bratcop]

I recently bought an ElmScan ISO off fleabay to start tuning my stroker. I believe(d) that my 01 Jeep GC was iso compliant, however I can't get the thing to read. I got a little information for about 6 minutes, including long term fuel trim, etc, but then it quit working. Has anyone had any luck using an ELM type signal interpreter hooked to their computer? I want to make this one work, however, if all else fails I will need to get another one. Does anyone know what OBDII protocol a 2001 GC Laredo 4.0L used. WJJeeps says "Chrysler uses ISO 9142-2 OBDII Communications Protocol" however, that is one of the few places I see 9142-2 listed. I usually see 9141-1 as a popular protocol. Any help here would be beneficial.

Bratcop

[amcinstaller]

is this item a programmer type thing or just a reader?? does the vehicle still run proper with no check lights??

[gmakra]

I would check with Craig Moates @ http://www.moates.net/index.php?cPath=31.
He might be able to steer you in the right direction

[SilverXJ]

He isn't dealing with some programmer issue or any "chipping" thing. Its a reader only. It can read codes, view live sensor data, data logging and reset the check engine light.

[gmakra]

XJ understood, I was just saying Craig is a knowledgeable guy and quite helpful and that maybe he could steer him to the answer.

[SilverXJ]

Bratcop, from your favorite website: http://www.wjjeeps.com/faultcodes.htm

Chrysler uses ISO 9142-2 OBDII Communications Protocol

I am also having a similar problem with a unit I just purchased by Autoengunity. I tested it on a 2004 WJ (seeing as my XJ is still engine less), and it logs fine for 20 or so minutes then loses connection. Mine is a direct to USB unit, and the only way I can establish connection again is if I turn the WJ off and then restart it. Restarting the PC does nothing nor does unplugging the USB device. I haven't had a chance to test it on another vehicle yet, but I am leaning toward the USB device being faulty.

Also, I seem to remember some of those ELM type scanners having a some sort of chip that doesn't work 100%. I.e. not the genuine article.

[bratcop]

Good dig, Silver.....
That is where I found the protocol I was checking on. I had not seen that protocol before, so I was asking about it on here. The Jeep runs great, I just want to check on the fuel trims and see about installing the PSC1-003. I would tune to zero the trims first, then get a wide band. I need a well respected OBDII reader, and what I got isn't working yet. I am still trying...any input is helpful...

Bratcop

[SilverXJ]

Good dig, Silver.....
That is where I found the protocol I was checking on. I had not seen that protocol before, so I was asking about it on here. The Jeep runs great, I just want to check on the fuel trims and see about installing the PSC1-003. I would tune to zero the trims first, then get a wide band. I need a well respected OBDII reader, and what I got isn't working yet. I am still trying...any input is helpful...

Bratcop

Even with well respected (Autoengunity) you may still have problems as I am. My main problem is that I can't find another vehicle to test it on to verify the problem, as my ZJ is an OBD I 95. Have you contacted the seller yet? I went with the Autoengunity because you can upgrade it to rear manufacturer specific codes on Jaguar and Jeeps, which I primarily work on.

[bratcop]

The seller was a guy on fleabay. I have shot emails back and forth and of course it worked fine on his 99, so I will heat the garage, use the free software he suggested today. I will let u know.

Bratcop

[hatem61]

Hi,
Hope you resolved your problem.
Only came across the thread just now.
Grand Cherokees from 1999 uses a protocol that is OBDII compliant, that protocol uses variable pulse width until the new model GC appeared with the mandated CAN communication protocol.
If it worked fine in the beginning, I do not see a communication protocol mismatch, but I would suspect a scan tool problem or the communication circuit first.
Could you try it on another car? Many vehicles of that era used the same protocol.
Good luck

[bratcop]

Well, I finally got it working. I didn't do anything special, just tried it again, and viola. I found my long term trims to be -4 to -6, so not to bad. I noticed, however, that my absolute throttle position never goes below 16%, and all the way to the floor it only reads 78%, obviously that is only a range of 62%. Would that indicate a bad TPS? I would have thought that it should start at 0 and peak somewhere near 100%. Anyone got any ideas on that?

[SilverXJ]

Did you test the voltage output on the TPS?

[SilverXJ]

Autoenginuity is finally RMAing their device. After 4 months of dealing with them they finally agreed to RMA it. They never return call either. They get a big F

[lafrad]

Well, I finally got it working. I didn't do anything special, just tried it again, and viola. I found my long term trims to be -4 to -6, so not to bad. I noticed, however, that my absolute throttle position never goes below 16%, and all the way to the floor it only reads 78%, obviously that is only a range of 62%. Would that indicate a bad TPS? I would have thought that it should start at 0 and peak somewhere near 100%. Anyone got any ideas on that?

Usually those percentages are just a percentage of the full 0-5V range.

its very rare that WOT on the blade will reach 5V, as that would loose resolution (what if it went further? what if the sensor was a little off to start with?)

same on the low side.

I would assume that if you get a constant sweep of readings from closed, all the way to WOT, its fine.