If the engine is still in the vehicle, all you would need to do is supply a power to the battery cable, and press the button on the cluster, and it should power on, as long as all the fuses are in place.
2008 Trailblazer Atlas Engine Noise
- Thread starter Red955i
- Start date
Thanks, I found an engine today with only 71,000+ confirmed miles for $1000 delivered. Can't beat that. Now I'll take your other suggestions and change some parts before I install. As usual, many thanks
One more question...(sorry) .... I have the VIN for the vehicle the engine supposedly came out of which checks with the mileage quoted. It still has the computer attached....but... Is there are part of the VIN stamped in an LL8 to confirm that the engine matches the VIN I was given. I saw the file posted which shows an Engine ID...(like on some early small blocks) but is that sequence # supposed to be part of the vin? This engine does not have tags where those are shown. It does have a bunch of numbers stamped in the pad back where the trans mounts on drivers side. Any clues?
Attachments
OK, you can read a VIN from the PCM with an OBD service 09 pid 02 request. Got an obd2 bluetooth or usb adapter and some idea of how to use it? I use an android serial terminal app for bluetooth written by Kai Morich. Anyway here is the dirt.... I haven't tried this benchtop but I see no reason it would not work. This is for a 2002 PCM, not sure what you have there so you would need to confirm pins to power up. The 2002 PCM needs 2 power sources out of the 4 to begin communication. Power to C1 pins 20 and 21, ground to C2 65. Serial data is on C1 pin 59.
I suppose you could just swap the PCM into a vehicle for the test also??
Once you have the elm327 connected to the PCM the commands I use are....
AT H1
AT S1
AT SH 68 6A F1
0902
That's it. The PCM will spit out a block like seen below in my log file. The 3rd byte after the timestamp idetifies the sender, '10' as the PCM. The 4th and 5th bytes are an acknowledgment of the 0902 request. The 6th byte is a sequential block number of the 4 bytes that follow. The 7th through 10th bytes are the VIN, represented as the hexadecimal equivalent of the ascii value of the digit or character. The last byte of each line is a checksum.
So pulling out the data we want from this otherwise gibberish my VIN as represented here is...
31 47 4E 44 54 yada yada yada down to the last line. Pull up an ascii table and convert from hex to characters and we have 0x31 = 1, 0x47 = G, 0x4E = N, 0x44 = D, 0x54 = T, and so on down the line.
14:00:44.441 Disconnected
14:00:59.646 Connecting to OBDII ...
14:01:00.797 Connected
14:01:07.171 ath1
14:01:07.171 OK
14:01:07.171
14:01:07.171 >ats1
14:01:09.644 OK
14:01:09.644
14:01:09.644 >atsh686af1
14:01:17.260 OK
14:01:17.260
14:01:17.260 >0902
14:01:20.400 48 6B 10 49 02 01 00 00 00 31 69
14:01:20.400 48 6B 10 49 02 02 47 4E 44 54 E4
14:01:20.400 48 6B 10 49 02 03 31 33 53 36 32
14:01:20.405 48 6B 10 49 02 04 32 32 32 34 E5
14:01:20.414 48 6B 10 49 02 05 31 34 31 32 AA
14:01:20.488
14:01:20.488 >
14:03:40.239 Connection lost
That's great info thanks... My old engine is in the car but every wire is disconnected and the battery is removed preparing to pull engine. So would have to backtrack to put the Replacement Engine's ECM in there. I was wondering if that would even work as the VIN wouldnt match the key???? As for the bench I've worked with Kent-Moore harnesses an breakout boxes so I know people that have the programs and harnesses to read/program the ECM on the bench can read it. I believe without those special harnesses I would need to get an obdII port and wire it. The other thing I am not sure of is when you read that data from the ECM is it stored in the ECM? When the ECM is in the car, it talks to the Transmission Controller (if equipped) the body Control Module, the ABS Control etc and even the dash. So while you may retrieve mileage when tapped into OBDII is it really in the ECM? or is the ECM retrieving it from elsewhere?
Thanks for your help
Thanks for your help
You know where it's coming from by reading the 3 byte header of the SAE J1850 VPW message. Every message has this identifying header that declares what kind of message is it, how important is the message, who the message is intended for, and who is sending the message. If the PCM had requested the data from somewhere else that request would be seen on the data bus.
Ok so the "10" in your example is telling me the PCM is storing the VIN. Cool. Now what about mileage that appears on the dash? DO you know whether the PCM or what other module stores that?
Mooseman
Moderator
Mileage is kept in the gauge cluster.
If a PCM is from the same year, it would still work. Just have to do a security relearn. It can be done without a scanner. Using the PCM with the engine it came with would avoid having to do a CASE relearn.
huge problem after PCM update / calibration (PCM Security Relearn)
If a PCM is from the same year, it would still work. Just have to do a security relearn. It can be done without a scanner. Using the PCM with the engine it came with would avoid having to do a CASE relearn.
huge problem after PCM update / calibration (PCM Security Relearn)
Of related interest (maybe). During vehicle operation the PCM sends incremental distance values to the odometer system. Quite frequently. I have not yet worked out the specific units it is using. Also during vehicle ooeration the instrument cluster reports the odometer reading to the class 2 data bus. Not so frequently though. I'm unsure what the purpose of this odometer report is.
My understandings from when I was a tech at GM, the mileage is stored, and calculated, in another location. This was done on purpose so that people couldnt do roll backs with eBay speedometers for warranty purposes, or lease purposes.
It was also used for when a vehicle would come in with a completely corrupted speedo, so the new speedo could be programmed with actual mileage.
It was also used for when a vehicle would come in with a completely corrupted speedo, so the new speedo could be programmed with actual mileage.
Of course it leaves open the question of where it gets that VIN. Is it only programmed into it? Or are there operations that it does to acquire that VIN, like during a security relearn. I know this much, because I have captured the serial data and can read and translate it. Early on when the engine is being started the BCM broadcasts the VIN over the serial data bus. It does so without any module requesting it. However, very shortly later I have seen the Supplumental Restraints module request the 2nd through 5th character of the VIN and receive it from the BCM. And if you are testing communications and have the instrument cluster up and running without a BCM present on the network then the cluster repeatedly requests the full VIN number.
I find this stuff fascinating.
Did you have any idea of what those stamped #'s are in my second picture? I'm used to "old" Chevy's where the VIN (or part thereof) is stamped somewhere into the engine. Supposedly there is a tag (not stamp) but its gone on both engines. Luckily, when they pulled the engine I bought they only took off AC, PS, & Alternator. They left computer, fan, manifolds throttle body etc. The VIN provided and actual salvage auction match the claimed mileage. But it dawned on me, if there's no stamp, what to stop them from claiming every other 2008-2009 4.2 they sell is related to the same VIN with the same low miles if there's no computer attached to confirm the VIN. Its not exactly the most honest industry
No.... but they dont appear to either on my original car I got from my friend who is the original owner
I should have read the post first I guess. I see now it wouldn't match the vin. I can see mine is stillthere got the sticker after 20 years!
xavierny25
Member
xavierny25
Member
Off topic again! New Yorkers are hard at work to keep there 360's on the road, @Uncleenvoy is currently in the final stages of putting his transmission back together and hopefully back in his trailblazer. He's just down the road from you in Laurelton.
I'm in Bensonhurst Brooklyn keeping my 08 Envoy on the road as best I can. My brother-in-law with the SS is in Staten island which I just recently got done putting in a new starter and new steering rack lines that busted in the process. @KEEBZ489 is also just off the belt parkway iirc not to far from uncleenvoy.
Think I'm going to start a nyc member check in thread.
I'm in Bensonhurst Brooklyn keeping my 08 Envoy on the road as best I can. My brother-in-law with the SS is in Staten island which I just recently got done putting in a new starter and new steering rack lines that busted in the process. @KEEBZ489 is also just off the belt parkway iirc not to far from uncleenvoy.
Think I'm going to start a nyc member check in thread.I was very lucky I did all the underhood stuff but wasn’t looking forward to doing the under the truck stuff. I work in a heavy truck shop in the office and was fortunate to get one of our former workers who is great at this stuff to come over and help. What would scare many off is just another day for him. (If you think this is hard work on heavy trucks where one guy is pulling transmission 3 times their weight) Next weekend I have to get him back for the reinstall