OBD2 not sending?

#1
Hi. I’ve tried to search the forums for this issue but don’t see it. If anyone can point me in the right direction it’d be great.
I have a wireless (WiFi) ELM type scanner. It works great in my wifes Pontiac GrandAm. But in my 2004 Trailblazer, it will send data until the outside temp, ( and maybe the wiring?) gets over a certain temperature. Then the signals from the OBD2 start coming intermittently then stop all together. In the summertime when it’s over, say 79°F, it doesn’t send any data at all. Is this a common issue, and what can I do to fix it?
When the data stops transmitting, I can take the reader and connect to my wife’s car, and it works no matter how the long the car runs or how warm it is.

Thanks in advance for the help.
 
#2
Thats an odd case. Never heard of temperature affecting it. I have several of the readers and they have always worked in whatever vehicle or conditions. I know my Scanguage works year round in my TB
 
#3
Sounds like there may be a problem with the wiring, and when it gets warm, things expand enough to give you an open circuit so communication is cut off.

Does anything else behave strangely when things warm up? In hopes of a relatively easy fix, you could try checking the wiring near the plug, see if anything looks out of place, any breaks in the insulation. If no problems found there, it becomes a more complicated hunt.
 
#4
Try unplugging and reconnecting the PCM. Could be a dirty or corroded connector (but you'd think when it's running and hot, that would affect it). Another possibility is a module somewhere shorting out the databus. Look for the main databus comb connector (sp205), which is basically the hub. Then jumper the DLC, PCM and BCM only. You need the BCM to power on the PCM. These should help you.

SP306 will be disconnected when you remove the comb from SP205 but if something connected to SP306 is buggering things up, then you'll need to try to isolate the defective module.

BTW, did you try another scanner? These wireless adapters can go bad.
 

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#5
Try unplugging and reconnecting the PCM. Could be a dirty or corroded connector (but you'd think when it's running and hot, that would affect it). Another possibility is a module somewhere shorting out the databus. Look for the main databus comb connector (sp205), which is basically the hub. Then jumper the DLC, PCM and BCM only. You need the BCM to power on the PCM. These should help you.

SP306 will be disconnected when you remove the comb from SP205 but if something connected to SP306 is buggering things up, then you'll need to try to isolate the defective module.

BTW, did you try another scanner? These wireless adapters can go bad.
Thanks,
I’ll try and do what I can. Your info sounds a bit to advanced for my trouble shooting skills, but if don’t find anything I’ll pass your info on to my mechanic.
If my ELM is bad, it came that way. Lol. I saw this issue as soon as I received it in the mail and started using it.

Sounds like there may be a problem with the wiring, and when it gets warm, things expand enough to give you an open circuit so communication is cut off.

Does anything else behave strangely when things warm up? In hopes of a relatively easy fix, you could try checking the wiring near the plug, see if anything looks out of place, any breaks in the insulation. If no problems found there, it becomes a more complicated hunt.
I haven’t noticed anything else acting strange as it gets warmer. I’ll check all the wires I can see at the OBD2 plug.


Thanks everyone.
 

budwich

Well-Known Member
#6
what app are you using? There are status lights on the elm adapter... what do they show? Further, some apps give the status of the obd device somewhere in the "menu areas"... have you checked them? Still, further the wifi status is also shown in the computer device somewhere... what is it saying.

Still further, I tried a wifi elm device and it lasted about two attempts before it had problems... ultimately, I took it apart and found a small ic blown. Not sure that wifi based interfaces are as "robust" as the bluetooth ones. I assume you are using an apple based app device.
 
#7
what app are you using? There are status lights on the elm adapter... what do they show? Further, some apps give the status of the obd device somewhere in the "menu areas"... have you checked them? Still, further the wifi status is also shown in the computer device somewhere... what is it saying.

Still further, I tried a wifi elm device and it lasted about two attempts before it had problems... ultimately, I took it apart and found a small ic blown. Not sure that wifi based interfaces are as "robust" as the bluetooth ones. I assume you are using an apple based app device.
All the status lights are working and blinking like they should on the adapter and the WiFi is connected (green WiFi indicator in app). I am on iOS device using the “4-Stroke” app, upgraded to premium. The device worked fine in other vehicles I plugged it into so far.
I’ll have to do some more experimenting in other cars during different weather, but I’m inclined to blame the wiring in the Trailblazer. I’m already running this car with zero gauges due to the faulty stepper motors they used.

I tried “OBD CARDOCTOR” app, but to me it was lacking and the ”premium” version features weren’t worth what they want to charge.

Is there any other apps you’d recommend that work with these adapters?
 

budwich

Well-Known Member
#8
wiring could be the issue... but does the app give you the status of the interface. All you have provided so far is to indicate the status of the "wifi layer". The app and the exchanges there after "sit above that layer"... meaning you could have wifi connectivity but significant erroring such that the higher layers of the protocol are not happy. For instance, on torque using bluetooth, the bluetooth "layer" indicates that the elm device and the app/tablet/computer are connected, yet at the higher layer, at least android there are / can be issues such that odb portion is not connected and shows in the "status" of torque that it is not connected. Just trying to isolate where the possible issue might be so that you can look at the "wiring" at a given area.... my guess one of the pins in the connector is not seating well into the elm device.
 
#9
I’m already running this car with zero gauges due to the faulty stepper motors they used.
To me, that's a clue right there. None of the gauges work? The likelihood that ALL stepper motors fail at the same time is nil. The cluster may be shorting the databus when it gets hot. Since it's not working, try pulling it out and see what happens.
 
#10
To me, that's a clue right there. None of the gauges work? The likelihood that ALL stepper motors fail at the same time is nil. The cluster may be shorting the databus when it gets hot. Since it's not working, try pulling it out and see what happens.
The gauges didn’t fail all at once. It was gradual, one by one failure over a few years, after the factory warranty expired of course. These are the same steppers that were covered under a recall in full size trucks made during the same time frame, but no recall was made for the trailvoys.

The ELM device does transmit data for a little while each time I try, before it stops. Maybe my computer is dying?

How do I test the pins at the connecter?
 
#11
One of the pins is ground and another is 12V+. I'm not at home so I don't have access to the schematics but you can download them from the link in my signature. That will tell you the wire colours at the OBD connector. Or Google for an image of the OBD connector with pin designation, which is standard for all vehicles.

Anything is possible. Does anything happen when the OBD stops? Engine keeps running or any other weirdness? Do the lights on the adapter stay on? Do you lose connection to the adapter or just the PCM?
 

budwich

Well-Known Member
#13
back on your problem. Not familiar with the app that you are using, and your "problem description" might be a little "thin".... can you provide more details... for instance, I assume that you are reporting that the interface "stops sending data", what data, all data, real time data, freeze frame data,?
Further, on some apps, you can "query" faults codes / check engine status, IM status... do these queries work / does the app support them? IF not, what happens when you attempt them? You might have to post some screen shots of what you are seeing.

As for the connector pins, lots of times the pins themselves have been pushed out of position, check all of them to ensure they are seating appropriately.

Lastly, a lot of elm devices (wifi and others) are under $10, you might want to just buy one and cut your time / effort by ruling out the wifi interface... "works in other cars" doesn't really help do that as each auto maker does its own thing in how they implement the interface and a "non-licensed third party" has to reverse engineer. My interface worked on some fords but not another (I had to use a wired interface then), and worked on TB, toyota.
 
#14
One of the pins is ground and another is 12V+. I'm not at home so I don't have access to the schematics but you can download them from the link in my signature. That will tell you the wire colours at the OBD connector. Or Google for an image of the OBD connector with pin designation, which is standard for all vehicles.

Anything is possible. Does anything happen when the OBD stops? Engine keeps running or any other weirdness? Do the lights on the adapter stay on? Do you lose connection to the adapter or just the PCM?
The TB still runs and drives normal after the data transmission from the ELM to the “4 Stroke” app stops. There is still power to the device, and it shows connect via WiFi, but the real time data, freeze frames, emissions readiness stops on the app.

back on your problem. Not familiar with the app that you are using, and your "problem description" might be a little "thin".... can you provide more details... for instance, I assume that you are reporting that the interface "stops sending data", what data, all data, real time data, freeze frame data,?
Further, on some apps, you can "query" faults codes / check engine status, IM status... do these queries work / does the app support them? IF not, what happens when you attempt them? You might have to post some screen shots of what you are seeing.

As for the connector pins, lots of times the pins themselves have been pushed out of position, check all of them to ensure they are seating appropriately.

Lastly, a lot of elm devices (wifi and others) are under $10, you might want to just buy one and cut your time / effort by ruling out the wifi interface... "works in other cars" doesn't really help do that as each auto maker does its own thing in how they implement the interface and a "non-licensed third party" has to reverse engineer. My interface worked on some fords but not another (I had to use a wired interface then), and worked on TB, toyota.
I thought I was narrowing the problem to the Trailblazer, by moving the wireless ELM from the TB after the “malfunction”, and connecting to my wife’s Pontiac GrandAm (or other cars) and seeing it still function properly.


Thanks for everyone’s help. I promise I’m not trying to be vague on purpose. After today, I’m taking the rest of the week off work, so I may break down and buy a more proper wired OBD2. My son has a one, but all it shows is any stored codes and freeze frames, but no real time data.

I’ll post some screenshots, and maybe a short screen capture video from the app later this week.
 

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budwich

Well-Known Member
#16
thanks for the additional info. Not trying to be "harsh"... just trying to get as much info about what is the problem and what isn't the problem to see if anything stands out.

For instance, on my "torque" when it is receiving / presenting real time data, there is a flashing "led" in the dial displays.... when those are not working for whatever reason (no longer updating), it stops flashing for that value / PID... does your app have anything like indication.

Still further, on the "torque" app, there are "tuning parameters" for the interface in terms of "baud rate" / data rate. (speed -> high / low, read rates, etc)... the torque guys know that the "multitude" of "elm knock offs" don't have all the "guts" of the official elm (which I do believe does not support wifi for android) so they have user adjustments that help the interface "survive" a session. As I indicated, the "wifI layer" may be perfectly happy showing the connection but just like your computer to the internet (over wifi), there are additional "communication layers" that sit on top of that "layer". Those may not be functioning properly or even significantly "erroring" such that those layers are never able to complete their communication to send valid data... hence, they could be just retrying repeated and not providing any indication that there is a problem... depending on how well the program designer has setup the internals / checks.

ONE LAST NOTE:
this taken from the "4 stroke page" on adapters... quote "Most inexpensive generic WiFi OBD Adapters use the same internals and will support sensor read speeds of five requests per second. We have tested against several of these adapters on multiple cars and they have all worked identically in our case." This would appear that they are aware of some "limitations" of the adapters... the question would be how extensive is their test and further still how many years back did they go in terms of vehicles. Their page only shows 3. Which one are you using which I don't think you mentioned / showed.
 
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#17
It looks like it was the adapter overheating and failing. I bought a wired reader and it read fine today during the hottest part of the day. Thanks for everybody’s input on this.

I should have seen the red flag when I tried to load the software from the disc that came with the adapter and found it had a malicious virus on it.
Moral of the story, don’t buy cheap/knockoff ELM adapters.
 

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