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Torque » Torque OBD ECU Scanner » Torque Discussion / Ideas » GM Cam Retard Offset PID Found!

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Author Topic: GM Cam Retard Offset PID Found!
SoonerCentral
Member
Posts: 6
Post GM Cam Retard Offset PID Found!
on: December 26, 2014 (GMT)

[01/03/2015] This has been edited to correct for mistakes when dealing with negative offsets, and I’ve added the Torque settings to do it a lot easier at the end.

Firstly, big time credit to OBD9141 on the ScanTool forums for posting the commands needed to access this PID. And to rhbguy for reposting it there or I wouldn’t have seen it, as well coming up with a conversion factor that puts this “damn close” to what his CRP123 reads.

You start with a Bluetooth OBDII Adapter. I used a cheap Vgate off of Amazon, which seems to work just fine, but will be buying the higher end Scantool MX “just because”. Install the Elm Basic terminal from the Google Play Store. There is another called Elm327, but I found it to be less than worthless.

Plug the adapter into the vehicle and get it paired with your phone. Loosen the distributor slightly so you can adjust it, then start the engine and let it warm up to normal temp. Now open the Elm Basic terminal and let it connect to the previously paired adapter. Then type in the following commands, in uppercase, hitting the Send button after each line:

ATZ
ATSP2
ATSH6C10F1

If you just stay in the terminal and do nothing else with the adapter then you will not need to issue these commands again.

Time to rev up the engine. Alldata said 1k RPM for my 99 Suburban, but I’ve seen various posts that said 2k for that year. Now type:

22130101

And hit Send. You should receive a string that looks like this:

62 13 01 AA BB

AA and BB is the signed data in hex. If AA is 00 to 7F, then the distributor is too far counter clockwise (positive offset). If it’s FF to 80, then you are too far clockwise (negative).

If AA isn’t 00 or FF, then adjust the distributor slightly and go back to “rev up the engine” above. Otherwise it’s time to look at BB.

If AA is 00 then turn the distributor very slightly clockwise to decrease BB. If AA is FF, then turn it counter clockwise to -increase- BB (signed word).

Perfect is both AA and BB at zero, but in reality that is seldom achievable.

— end edit and now addition

Here’s the easier way with Torque:

– Buy the app, just do it!
– Get it connected and working with your ODB2 adapter.
– Create a custom PID. The critical parts are 221301 as the Mode/PID string, a negative minimum value (-100 should be fine), and the equation is ((Signed(A)*256)+B)*0.024
– Add a real time display to show this PID along with the engine RPM.

Rev engine over 1k, adjust within +/- 2.0, slightly tighten, and retest. I say slightly, because it’s entirely true that the mere act of doing so will generally change the setting. On a 5.7, with the wiring harness in the way…

Capp777
Member
Posts: 2560
Post Re: GM Cam Retard Offset PID Found!
on: December 26, 2014 (GMT)

Drop the 01 at the end of the pid given and use
header 6C10F1 (or Auto)…

((Signed(A)*256)+B)*0.024

((Signed(A)*256)+B)*(720/32768)
((Signed(A)*256)+B)*(768/32768)
((Signed(A)*256)+B)*(1000/15625)
((Signed(A)*256)+B)*(1/16)

ATSH6C10F1 set header to 6C10F1.

ATSP2 set protocol 2 (VPW). Torque will
set the correct protocol when you connect
so all is needed is to create a custom pid
and snap the throttle over the threshold rpm
for value updates.

ATZ resets the adapter.

Edited.

SoonerCentral
Member
Posts: 6
Post Re: GM Cam Retard Offset PID Found!
on: December 26, 2014 (GMT)

Quote from Capp777 on December 26, 2014
Drop the 01 at the end and try
header 6C10F1 (or Auto)…

((Signed(A)*256)+B)*0.024

for signed values.

I did try dropping the 01 once, but it was getting dark and I called it a day. It’ll be a bit before I can try this again as the wife took off with the Suburban and the adapter. Think I heard something about shopping, and her Tahoe not being big enough. And I was afraid that if I went out there she’d ask me to hookup the utility trailer too :(

Here’s what the guy was using in OBDWiz when he came up with the initial conversion:

OBD Header…..ECM
OBD Mode……..22
PID Number……130101
Formula…………(B/100)*2.4
Receive offset…1
Priority……………Low.

That’s 1 byte for the mode, and 3 bytes for the PID. Torque puts that in a single field, but doesn’t allow for 4 bytes.
I highly suspect that OBDWiz is correct in that PID’s can be a full three bytes by themselves, but I’m not willing to pay for SAE J2190 just to find out either :)

Capp777
Member
Posts: 2560
Post Re: GM Cam Retard Offset PID Found!
on: December 26, 2014 (GMT)

The last byte (01) instructs the Elm327 to return
after one response. Not needed within Torque.
(Mode 22 addresses are two bytes from 0000
thru FFFF). Notice the response example given
didn’t include it.

If…

AA=04 and BB=A0 matches +26.0°
AA=02 and BB=AA matcges +15.0°
AA=00 and BB=E6 matches +5.0°
AA=00 and BB=5C matches +2.0°
AA=00 and BB=45 matches +1.5°
AA=00 and BB=2E matches +1.0°
AA=00 and BB=00 matches 0.0°
AA=FF and BB=D2 matches -1.0°
AA=FF and BB=BB matches -1.5°
AA=FF and BB=A4 matches -2.0°
AA=FF and BB=1A matches -5.0°
AA=FD and BB=55 matches -15.0°
AA=FB and BB=60 matches -26.0°

Then multiplier equals (720/32768)

If…

AA=04 and BB=55 matches +26.0°
AA=02 and BB=80 matches +15.0°
AA=00 and BB=D5 matches +5.0°
AA=00 and BB=55 matches +2.0°
AA=00 and BB=40 matches +1.5°
AA=00 and BB=2B matches +1.0°
AA=00 and BB=00 matches 0.0°
AA=FF and BB=D5 matches -1.0°
AA=FF and BB=C0 matches -1.5°
AA=FF and BB=AB matches -2.0°
AA=FF and BB=2B matches -5.0°
AA=FD and BB=80 matches -15.0°
AA=FB and BB=AB matches -26.0°

Then multiplier equals (768/32768)

If…

AA=01 and BB=96 matches +26.0°
AA=00 and BB=EA matches +15.0°
AA=00 and BB=4E matches +5.0°
AA=00 and BB=1F matches +2.0°
AA=00 and BB=17 matches +1.5°
AA=00 and BB=10 matches +1.0°
AA=00 and BB=00 matches 0.0°
AA=FF and BB=F0 matches -1.0°
AA=FF and BB=E9 matches -1.5°
AA=FF and BB=E1 matches -2.0°
AA=FF and BB=B2 matches -5.0°
AA=FF and BB=16 matches -15.0°
AA=FE and BB=6A matches -26.0°

Then multiplier equals (1000/15625)

If…

AA=01 and BB=A0 matches +26.0°
AA=00 and BB=F0 matches +15.0°
AA=00 and BB=50 matches +5.0°
AA=00 and BB=20 matches +2.0°
AA=00 and BB=18 matches +1.5°
AA=00 and BB=10 matches +1.0°
AA=00 and BB=00 matches 0.0°
AA=FF and BB=F0 matches -1.0°
AA=FF and BB=E8 matches -1.5°
AA=FF and BB=E0 matches -2.0°
AA=FF and BB=B0 matches -5.0°
AA=FF and BB=10 matches -15.0°
AA=FE and BB=60 matches -26.0°

Then multiplier equals (1/16)

For VPW header 6C10F1.. the ECU address is 10
and F1 is the tester address.

While in the pid editor, test the pid for the
returned hex code response.

The torque variables used will be dependent on
the byte positions in the hex response.

If the response matches the example given then
Torque variables A and B are correct.

If a P1345 dtc is set at +/- 26 degrees for 1999 (where one
tooth is ~27.7 degrees) ? … curious what value the
hex response reports at that threshold and which
equation comes closest. Not sure how well engine
will run at those thresholds though.

Edited.

cintakc
Member
Posts: 1122
Post Re: GM Cam Retard Offset PID Found!
on: December 27, 2014 (GMT)

Quote from SoonerCentral on December 26, 2014
Torque puts that in a single field, but doesn’t allow for 4 bytes.

torque enables output 4 byte requests
To do this, you need not create external PID manually, and create a file csv, which prescribe such your PID

SoonerCentral
Member
Posts: 6
Post Re: GM Cam Retard Offset PID Found!
on: December 27, 2014 (GMT)

Okay, with 221301 as the Mode/PID string, 6C10F1 as the header string, and (Signed(A)*256)+B)*0.024 as the formula, we get a response of 7F22130112 and constantly updating data if you hold the RPM up a bit.

I know that the closer you get this value to zero, the closer you are to exact specifications. But I highly suspect the formula is slightly inaccurate were A=00 with low values of B, and much more so if A=FF. More on why later.

But for the moment, it doesn’t matter. While holding your phone in one hand you can adjust the distributor with the other. Set as close to zero as you can reasonably get, and you are good to go.

I have some more info regarding ranges, limits, etc, and I’ll try to get it typed up later today. But I’m still not sure if the data is a one or two complement number.

Capp777
Member
Posts: 2560
Post Re: GM Cam Retard Offset PID Found!
on: December 27, 2014 (GMT)

The 7F22… is an unsuccessful message?

My understanding is that the results are
not accurate unless the rpm is greater than
1000, which might explain behavior of the
7F22… message.

Edit:

If you prefer a single snapshot hex value you
could try using a send command display
with its test feature during throttle snaps.

SoonerCentral
Member
Posts: 6
Post Re: GM Cam Retard Offset PID Found!
on: December 28, 2014 (GMT)

Sorry, between the holidays and having to dig up my main sewer line, I’ve just not had time to play with this much. And then it snowed, so I’ve got a muddy mess out here.

With the engine at idle I hit the test button within the PID editor. That returned the last recorded offset and the 7F23130112 response. As soon as you rev it up a bit the data begins to change but the response code does not. As I take it up over 2k RPM the data begins to stabilize roughly 0.2 deg lower than the initial value.

I have Alldata for my vehicles, and I’ve seen the excerpt from the actual GM procedure for this. Nowhere does it say anything about “snapping the throttle”. They heavily imply holding it exactly at 1000 RPM, which, using the GM Tech2 scantool, you can command the engine to do.

And that makes sense. Due to slop in the timing chain the value will change slightly at different RPMs, even on a fresh engine. So any procedure would pick a specific RPM for consistency purposes.

What I don’t know yet is how the CPU is treating this data internally, versus how it sends it you, versus how you display it. I need to confirm something that I’m pretty sure I saw, but it was getting dark and I was out of time.

From the terminal I know that A=00, and B increases as you go slightly positive. I have little doubt that A will increase to 01, 02, etc if you keep going. But I’m not so sure about the negative. I know that A will turn FF, and I have little doubt it will decrease to FE, FD, etc.

But…my admittedly fuzzy memory is telling me that when A=FF, B started out very low and -increased- as I went slightly further clockwise. If you were directly referencing bytes within a word, B would be FF when you first went negative, and decrease as you went more so.

While I’ve little experience with the current crop of vehicle CPU’s, I started with assembly on a IBM 370 mainframe, punch cards, and have done a bit of embedded CPU work. This kind of data structure might be uncommon now, but it didn’t used to be.

I can easily confirm this part, and will when I get a chance later this week. Figuring out if it’s one or two’s complement will take a bit more work. I’m sure I can rig a wedge up to hold the throttle at a fixed RPM 1k or better. And find somewhere that I can lay something to make a fixed reference spot on the distributor.

Now I just got a really dirty look because I eyeballed my wife’s seamstress tape, with millimeter marks on one side. She won’t let me use it to measure circumference, said I get it dirty, and I don’t have calipers that big. So, feeling froggy, I said, well, how about letting me cut just a little tiny bit off of one end, so I can silicon to the distributor?

Whistles to self…

Fire up the vehicle, set it zero offset, and now you can record data versus distance traveled. And that’s easily convertible to degrees for comparison.

Give me some time and I’ll get some more info. Grandpa is too busy getting in trouble at the moment :)

Capp777
Member
Posts: 2560
Post Re: GM Cam Retard Offset PID Found!
on: December 28, 2014 (GMT)

Thank you for your efforts… a lot of people
have requested this function for Torque.

If it turns out to be a two’s compliment two byte
response my previous posting of a modified
scaling based upon your observations is a little
different than the 0.024.

(I’m the kind of guy whom would makeshift a
laser pointer on an old distributor cap to split
hairs :-) a = b tan A :-) )

Where: [________ .

a = movement desired in inches [
b = 36 inch reference point (yardstick) _______ .
A = movement desired in degrees °

At a point 36″ (yardstick) from center of distributor
a 2° shift is ~1.25″ movement perpendicular (90°)
from that point on the sight line and 26° shift is
~17.5″ movement.

Again Thanks!

Edit:

Snapping the throttle above 1000 would update
the values when issueing the command in terminal
mode without a wedge… snap, check last offset, adjust
and repeat until within spec.

Still curious where the hex data is coming from
if you are not getting 62… back. 7F22…
would not provide for aa and bb.

Edited again.

SoonerCentral
Member
Posts: 6
Post Re: GM Cam Retard Offset PID Found!
on: December 30, 2014 (GMT)

Quote from Capp777 on December 28, 2014
Thank you for your efforts… a lot of people
have requested this function for Torque.

I can’t take credit for the most important part…finding and publishing the darn codes :)

We are okay on the positive side right now, it’s the negative that has to be dealt with. That means I have to go loosen a distributor and slowly adjust to negative while watching the data. Just find out whether B resets to 00 or FF when I first go negative (A=FF), which will be easy enough as you slowly turn it with the engine RPM held relatively stable (even a helper will do). I’ll try to get that done in the next couple of days. I’m just really busy right now, and everything seems to be breaking at once, literally :)

Snapping the throttle, while it will work to bring it well within spec, is “not the optimum procedure”. Because of slop in the timing chain as the engine revs up and down, it’s not going to be as consistent. From what I saw driving the other day you can probably tell just how stretched that chain is based on the difference between 1k and 4k RPM.

But it would let you do it “close enough” with one hand, no wedge, no helper, get ‘er done.

The hex data you asked about is coming from the Elm Basic terminal app when I query it manually. As to the 7F response within the editor, I have no idea. Never researched ODBII or Elm327 adapters (yet). But whether in the PID editor test mode, or as a real time display, you -are- getting the data back. It constantly updates as long as the RPM’s are up, and as I mentioned above, varies slightly with it.

I probably need to play with Torque, even there other than add tranny temp and play with this PID, I’ve literally not had the time to do anything. Because of your questions about the 7F response, I’m using the terminal for raw data.

What I really need to see is two separate displays, one showing calculated, another (or two, depending on what you can do in the PID editor), A and B separately either as hex or binary. No signed vs unsigned decimal, strictly raw data.

That would make it go a bit faster.

cintakc
Member
Posts: 1122
Post Re: GM Cam Retard Offset PID Found!
on: December 30, 2014 (GMT)

If the response 7F22130112, this means the wrong format command you issue and the block does not understand this and do not give you
You never tried to issue a request 22130101, could well need
Issue 22130101 created using the PID file csv, see what will give the block

Capp777
Member
Posts: 2560
Post Re: GM Cam Retard Offset PID Found!
on: December 30, 2014 (GMT)

Simple test using elm terminal…

Issue pid without the 01 to compare
response at idle.

If Torque receives the 62… response then
your equations will return data correctly
which you described as working.

The 01 tells elm327 to expect one line of
response. (adapter won’t have to timeout
waiting for a response before returning).

Also you might try adding the pids to
Torque’s file data logging to capture the
values as you slowly move the distributor.

Good luck with your other projects!

Happy New Year :-)

Edited.

cintakc
Member
Posts: 1122
Post Re: GM Cam Retard Offset PID Found!
on: December 30, 2014 (GMT)

Quote from Capp777 on December 30, 2014
The 01 tells elm327 to return first line of
reponse, ignoring subsequent lines.

not always at the end of 01 means a return to the previous line
for example in the protocol for Daihatsu all requests ending in 01
210001
210101
210201
210301
and t. d.

Capp777
Member
Posts: 2560
Post Re: GM Cam Retard Offset PID Found!
on: December 30, 2014 (GMT)

If I am interpreting Sooner’s comments
correctly… in the pid editor, without the
01, he is getting a 62… response with data
and 7F22… response following. Torque is
assigning variables to the 62… response
correctly and Torque display is showing
updating data (green light).

In terminal, with the 01 added, the 7F22…
is ignored and not displayed after the
62… response.

Just trying to build a mental picture of what
Sooner is seeing.

Based upon byte BB’s questionable response to changes, I
would create separate pids using the following
equations:

1. Signed(A)*256

2. B

Edited.

SoonerCentral
Member
Posts: 6
Post Re: GM Cam Retard Offset PID Found!
on: January 4, 2015 (GMT)

I did a limited bit of testing today, and here’s what we have:

– The data is just a signed word, most significant byte first. ((Signed(A)*256)+B)*0.024 works. Because I have doubts about the /100*2.4 conversion, I would guess that the further you get away from zero in either direction the larger the error. Doesn’t matter for now, as you want as close to zero as possible.

– If in the terminal you must issue 22130101 to get back data. Dropping the 01 and sending 221301 alone gets you the same 7F22130112 response that you see when testing the PID in the Torque editor.

– You can leave the header blank in the PID editor, and as long as Torque is already connected to the ECU it will work.

– I do not know what the true range is (min/max values), nor is it particularly important as long as you define a negative minimum.

I’m going to edit the initial post to reflect what I’ve found. It works, I’ve tried it on two separate Vortecs, albeit both are 1999.

B00R
Member
Posts: 2
Post Re: GM Cam Retard Offset PID Found!
on: January 25, 2015 (GMT)

Tahoe 96 with vortec not support this method?

lesmyer
Member
Posts: 3
Post Re: GM Cam Retard Offset PID Found!
on: June 23, 2016 (GMT)

Updated instructions in post #1 would not calculate a value until I changed OBD Header to “Auto”. This custom PID then displays a constant 0.0° for my 2001 Blazer. Unfortunately, I have already established my CMP Retard as 0.3° to 0.7° depending on temp and RPM, using 4 different softwares (Car Guage Pro, Dash Command, Scan XL Pro, and HP Tuners. They all agree with each other. Doesn’t appear you are there yet with a custom PID for Torque Pro.

Racer_X
Member
Posts: 2
Post Re: GM Cam Retard Offset PID Found!
on: July 15, 2016 (GMT)

Les, I thought I’d respond here instead of over on the Blazer forum because this is a little “techy” and app specific to this app and this forum.

Did you specify a negative minimum value? Are you getting any data for PID 221301? Have you tried 22130101?

Also, check to see if you’re getting any data at all, without the scaling factor. Use the formula “(signed(A)*256) + B”. That will display the binary integer the ECM is sending, without scaling. It should range from -32768 to 32767. And make sure with this formula that you set the minimum to a high negative number (-32000 is good).

If that returns a constant zero, I suspect there are two (or more) PIDs used by GM for this data. That would also be consistent with your description of getting this data with another app, where I thought you said there were two (or more) PID choices for “CMP Ret” and one had an asterisk on it.

I’ve been away from my “Oldsmo-Blazer” for a few weeks, and I won’t be back to it for another week or two. I’ll check more on this when I get back to it.

lesmyer
Member
Posts: 3
Post Re: GM Cam Retard Offset PID Found!
on: July 15, 2016 (GMT)

Yeah, I specified -100 as the min value. I also tried the 22130101 unsuccessfully. I got no data until I changed the OBD header to Auto. What I’m wondering is if the formula only approximates the value, and is somehow interpreting my 0.3°-0.7° actual as 0.0°. After all 0.024 in the formula is only 2 significant digits. Guess I could use 0.02359 (98.3% of 0.024) as a test to see if it changes the displayed output at all. What bothers me is that CMP retard will change with engine speed and temperature. My 0.0 reading on Torque never changed from 0.0.

Car Guage Pro is the app that has two different CMP retard choices. Dash Command, Scan XL Pro, and HP Tuners only have one choice.

To be continued at some point….. After all I do have four other ways to read my CMP retard if I wish to do so. Just always wondered why Torque did not include it in an otherwise very nice app. It has become kind of a hobby to me to determine what software does it and what software cannot.

Capp777
Member
Posts: 2560
Post Re: GM Cam Retard Offset PID Found!
on: July 15, 2016 (GMT)

You might want to test the pid while in
the pid editor (with the rpm above the
threshold for a proper response) to see
if a valid hex response is received.

The formula above is good enough to get
one within spec but is not exact to a calibrated
source. You will notice I suggested other equations
that may be closer but were never checked to
my knowledge.

The questions I have are what are your
test response bytes received and what
module is responding?

If your response is valid then we can calculate
a formula from the raw hex bytes and your
known current setting. (0.3 to 0.7°).

If its not valid you could try to run torquescan
to see if a pid can be found with a hex value
that’s close to what you seek.

Edit:

If you created a custom pid did you try…

Dropping the last 01 in the pid number. Torque
doesn’t require it but terminal mode commands
do.

Assuming your protocol is VPW… try
header 6C10F1.

To get a zero result your hex data would be
00 00. Since your stated value is positive your
hex data would have to be greater than 00 00,
e.g., 00 14.

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