I agree, I don't spend a lot of time on the grade school level relays and switches these days.
My current project is an Arduino that reads all messages on the serial data bus and I can choose any given message to trigger any given action that a Tech 2 could do in response, short of...
Getting back on topic, just in case anyone is interested.
Circled here is the actual resistor on an actual passlock sensor circuit board that varies from vehicle to vehicle and produces the variable voltage drop that the BCM sees and evaluates.
The component with the blue dot is the...
On a nice quiet street a thief could spend a half hour or more checking things out. Just might find your switch since it logically would be within a drivers reach. But if the truck dies in the middle of the road it's far more likely to draw attention to the thief as they try to get it restarted...
In that case I could set it to die in say .25 miles. Or once it reached a speed of my choosing. Maybe just cut the fuel if the rpm went above 1200. I can do any of this with my 05 Yukon if I choose to.
Better yet use a timed-off system that allows the fuel pump to run for like 2 or 3 minutes. Let them get out on the road then kill it. Their less likely to hang around trying to get it going again when they're dead in the middle of the road attracting attention!!
Just tossing this out here for what it's worth. The trouble with scanners is they don't always tell you the true status byte value but their intepretation. I read my codes hands-on, issuing the requests with a serial terminal so I see the actual response from the module, not some softwares...
You could look at your OBD2 port and see what terminals have wiring in them. If it is SAE J1850 VPW it will have wires at terminals #2, #4, #5, and #16. Google "OBD2 Pinout" to find a diagram of what wires are used for each of the possible protocols.
My guess is the SAE J1850 VPW protocol. That what GM was using mostly at the time. My 2005 5.3 LM7 Yukon uses J1850 exclusively.
Edit: I cannot say what was used for vehicles not sold in the USA. European models might be different?
Hell, when I was in high school in our auto shop we even had a machine that arced new shoes (drum brakes) to match the inside diameter of the turned drums!
Thanks, Swathdiver. I knew that ;)
My post was prompted by previous posts that claimed the max tire pressure was ONLY as a limit to be used when mounting a tire, and at least suggested that a tire should never be operated at that pressure. My example, at least on the face of it appears to...
The tires are the exact same tire sold with the truck as new. The door sticker is factory supplied. Are you suggesting they manufactured the truck with the wrong tires!!??
I did get the unknown driver etc message. I have the whole thing on video if you're interested.
The results seen at the cluster are very much the same, if not precisely the same when I initiate the event with phone and serial terminal and NOT the Tech 2.
Well lets see what shipping we're...
@George B
I have to have a healthy serving of crow for lunch here!! :)
I was quite surprised to see my cluster do the same at requesting SPS data.!! I need to pay better attention it would seem.
After seeing my own truck do the same I had a look at the data stream and saw the reason for...
So before seeing this video I had thought you only had this type of error on the Envoy.
That sure looks like something is bad with the tool.
For comparisons sake tomorrow I will make and post a short video of my Tech 2 and TrailBlazer requesting SPS data. For the 2002 TrailBlazer/Envoy I...
I HAVE swapped in a junkyard PCM with my TrailBlazer, ran the security relearn and it ran fine. Did it just for the experiment and recorded the class 2 data stream while doing it for later analysis. Also then swapped back my original PCM. I can get used PCMs here for under $20 at the Upull.
Well I have as you know a 2002 GMT360 and have literally used my Tech 2 hundreds of times including requesting SPS data with it and have never experienced any gauge drop or unknown driver events or anything like that.
I am still of the notion there is some hidden issue with your Envoy.
I am of the mindset of if there is not a specific reason or need to update a module I will not do so.
I did update a junkyard 2003 TrailBlazer PCM ($15) on the benchtop just to become familiar with the process as well as snoop the class 2 data bus during the event for curiosity.
While it sounds like it is leaking, the purge valve (one at the engine) leaking would not set a small leak code. It would set a code for purge flow while not commanded. A leaking purge valve would make the Evap test vacuum rise, not fall.
Check your UNLOCK relay. The rear doors are controlled by the BCM and have separate LOCK and UNLOCK relays.
When you use the front door switches or the key fob(s) the BCM gets a message on the class 2 bus to lock or unlock the rear doors.
The BCM also is notified of the PRND321 position and...
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