Accelerator position via the OBD II

dhrivnak · Nov 5, 2007

By any chance does anyone know if it is possible to determine the accelerator position through the OBD port on a 2004 Avalanche? I am trying to install a major mod to noticeably improve gas mileage and performance. I know this sounds like a long shot but I am installing an electric motor between the transmission and the differential. I have already installed batteries and a charging system allowing me to plug in to get about a gallon of energy from the wall for about $.25/gal. Then when I drive around town the system will try to use the electric motor to help push the truck saving gas.

A shop in Colorado has taken a 1999 Tahoe from 12 MPG to 19 on in-town driving and another person in Chicago has seen a 28% gain on a 1996 Blazer. But to my knowledge I am the first to try this on a newer GM truck. We we are tapping into the OBD to capture the accelerator postion, along with other data. Except in my case I am 99% sure what the system is seeing is the throttle postion, the postion of the throttle body not the postion of the accelerator.

I know we have some guys on this forum that have some deep technical knowledge and am hoping someone can point me in the right direction. Thank you

DamonCollins · Nov 25, 2007

yes...it is called the TPS and it is measured in % opened. (and yes, it's status is available through the OBDII port.)
Good luck!

FlaBouy · Nov 25, 2007

Yep... it can also be manually controlled with tools within HPT....

EDIT: I was travelling on the road yesterday and had to keep it short while I was driving. You are correct to assume the tuners log throttle position with a throttle position sensor (TPS). On the older Av's the throttle was cable driven, but on yours (and mine) it is drive by wire. The accelerator position is fed into the TAC unit located on the engine firewall next to the steering column. The throttle accuator unit drives the throttle plate by converting the accelerator postion switch output to as 0-5 vdc signal for throttle positioning. Get with DrX... I believe he did some work previously with the TAC unit output to correctly drive the 90MM throttle plate on a TB conversion he was doing for the Radix crowd...

PM me if you need further info....

Good Luck.

FlaBouy · Nov 26, 2007

BTW, I am in Tennessee for the next several weeks if you need to see what the HP Tuners package does on a 2004 AV. I can actually tune your truck while we are at it, since I hold a license for all 2004 Avalanches.

GT · Nov 27, 2007

Little late but.......You can log Accelerator Pedal Position if that's what you are asking. Or you can tap directly into the APP sensor output if you require an input for something linked to APP.

motodj · Nov 28, 2007

Dr.X, i noticed your sig has efi live listed..
just a vague question for ya, i have the hypertech now, and i am satisfied...
but, i got the opportunity to get an EFIlive tune (like a 100 bucks for another vin)
i believe i would be happier with that, than with the hypertech..

now my question for you is that my truck 2500, is pretty much stock, would a custom tune still be worth the effort of finding a dyno and doing a true "tune"?

#2 how easy is it to customize? i'm worried i'll be way overmy head here
#3 is there a starting point for a tune? i have looked for downloads and havent seen any "tune" files
#4 can you tune for economy, and use the tow/haul mode for an aggressive tune? i'd like to be able to "toggle" the tune

sorry to thread jack here

now as far as this electric motor, where can i see some info on this?
i'd give it a shot, i'm less than 10 mpgs in the city
i'm interested in doing a "green" mod too
Id like to see a list of parts if ya dont mind dhrivnak

thanks for inducing more modding fever

GT · Nov 29, 2007

motodj said:
Dr.X, i noticed your sig has efi live listed..
just a vague question for ya, i have the hypertech now, and i am satisfied...
but, i got the opportunity to get an EFIlive tune (like a 100 bucks for another vin)
i believe i would be happier with that, than with the hypertech..

now my question for you is that my truck 2500, is pretty much stock, would a custom tune still be worth the effort of finding a dyno and doing a true "tune"?

#2? how easy is it to customize? i'm worried i'll be way overmy head here
#3? is there a starting point for a tune? i have looked for downloads and havent seen any "tune" files
#4? can you tune for economy, and use the tow/haul mode for an aggressive tune? i'd like to be able to "toggle" the tune

If $100 for a licence will get you full access to EFILive whenever you want it, then it is definitely worth it. You can do a lot more than with a handheld. If this is not a one-shot deal, I would work on the tune myself before going for a dyno tune. Particularly on a stock truck. You can always do the dyno later if you still want to. There is definitely a learning curve. So, if you can tweak a few things at a time, that would be great.

You can use the Tow/Haul switch to toggle between "normal" and "performance" shift patterns that you have set up in the tune.

motodj · Nov 29, 2007

cool, thx,

as far as the tuner goes... sits in my friends shop just down the road
>:D

could resonably retune whenever i want... but without ownership in the programmer... i'd be at the mercy of the customer who owns it...

he has let 3 others do it at this shop.. so i've been offered too
he uses his for a diesel hd chevy, he pulls the big sleds for competition

some day i'll be askin ya for some starting points, but not now, i dont want the itch for a neccesary mod
:laugh:

thx again

jconsole · Nov 29, 2007

dhrivnak said:
By any chance does anyone know if it is possible to determine the accelerator position through the OBD port on a 2004 Avalanche?? I am trying to install a major mod to noticeably improve gas mileage and performance.? I know this sounds like a long shot but I am installing an electric motor between the transmission and the differential.? I have already installed batteries and a charging system allowing me to plug in to get about a gallon of energy from the wall for about $.25/gal.? Then when I drive around town the system will try to use the electric motor to help push the truck saving gas.?

A shop in Colorado has taken a 1999 Tahoe from 12 MPG to 19 on in-town driving and another person in Chicago has seen a 28% gain on a 1996 Blazer.? But to my knowledge I am the first to try this on a newer GM truck.? We we are tapping into the OBD to capture the accelerator postion, along with other data.? Except in my case I am 99% sure what the system is seeing is the throttle postion, the postion of the throttle body not the postion of the accelerator.?

I know we have some guys on this forum that have some deep technical knowledge and am hoping someone can point me in the right direction.? Thank you

i beleive we emailed each other outside of this site.

have you considered a motor built into the wheel? the reason i ask is what if the truck is still under warrenty/extended warrenty. if the dealer sees the mod they can void the warrenty for the whole truck. with the wheel motor you can just change it before bringing your truck in.

also as soon as i can get a day off i will be making calls to the irs and consumer affairs to see if the government can give us a tax break of somekind for this mod.

DamonCollins · Nov 30, 2007

jconsole said:
...if the dealer sees the mod they can void the warrenty for the whole truck. ...

not true....see the Magnuson/Moss Warranty Act

dhrivnak · Dec 25, 2007

Does anyone know what protocol the 2004 Avalanche OBD uses? I have a OBD reader and it seems to indicate it is SAE J1850 VPW and I would have thought it would use the newer CAN protocol. I was told the SAE J1850 was used before 2000. The reason I ask is it seems the Accelerator Pedal Position is not in the earlier protocol and the reader I have has not been able to find that code. Thank you

Tahoe Fox · Dec 25, 2007

not i... did a search pull up anything yet? if not, i'm sure someone on here would know

itsstopher · Dec 25, 2007

dhrivnak said:
Does anyone know what protocol the 2004 Avalanche OBD uses?? I have a OBD reader and it seems to indicate it is SAE J1850 VPW and I would have thought it would use the newer CAN protocol.? I was told the SAE J1850 was used before 2000.? The reason I ask is it seems the Accelerator Pedal Position is not in the earlier protocol and the reader I have has not been able to find that code.? Thank you

VPW

Look here

dhrivnak · Dec 25, 2007

Thank you for the prompt replies. This does not look encouraging as the interface module I was planning to use to tie into the OBD to read speed and the accelerator pedal postion. What the avalanche reports back is the throttle postion which due to the drive by wire is not necessarily connected to the accelerator. When cold the throttle will read 18% at idle yet while warm 9%. This means I will not be able to get electric assist under low levels of accelerator. I will keep digging and hopefully I can find a way around this problem.

ohiobellboy · Dec 25, 2007

man, learned something else today. after reading this I just had to go open my hood and look at the wires instead of a cable running to my TB. I never knew that about the TB being DBW.

dhrivnak · Dec 26, 2007

jconsole said:
have you considered a motor built into the wheel? the reason i ask is what if the truck is still under warranty/extended warranty. if the dealer sees the mod they can void the warranty for the whole truck. with the wheel motor you can just change it before bringing your truck in.

also as soon as i can get a day off i will be making calls to the irs and consumer affairs to see if the government? can give us a tax break of somekind for this mod.

I waited until my truck was out of warranty before i started the work. The warranty ran out at 36,000 miles and I started the work at 40,000. I am not sure how I would connect a motor to each wheel. Initially I was going to add 4WD by adding two electric motors to the front wheels but the hubs are different on the 2WD and it appeared there would be some extensive modifications. to make that work. Also finding a motor small enough to fit there and large enough for any meaningful torque was problematic. So I will replace the driveshaft with an electric motor and two smaller drive shafts. If it dies not work then I can unbolt everything. So far with the exception of two small brackets welded to the frame to hold the rear motor mount, everyting is bolt on and bolt off. I still have some updating to do but I am trying to keep people up to date on the progress on my web site at www.hrivnak.com.

FlaBouy · Dec 26, 2007

dhrivnak said:
Thank you for the prompt replies.? This does not look encouraging as the interface module I was planning to use to tie into the OBD to read speed and the accelerator pedal postion.? What the avalanche reports back is the throttle postion which due to the drive by wire is not necessarily connected to the accelerator.? When cold the throttle will read 18% at idle yet while warm 9%.? This means I will not be able to get electric assist under low levels of accelerator.? I will keep digging and hopefully I can find a way around this problem.

HPTuners show a whole range of Thottle/Pedal Position Sensor/Switch circuits with DTC's tied into Range/Performance.... The SES codes thrown are P2120, P2121, P2125, P2126, P2130, 2130, P2131, and P2135....? ?This is in addition to the throttle plate sensor and VSS (vehicle speed sensor)

The TAC module looks at APP (accelerator Pedal Position) for the following:

APP Average? ? ? ? ? ? ? ? ? ? 0-100%
APP Indicated Angle? ? ? ? ?Counts
APP Sensor 1? ? ? ? ? ? ? ? ? ?0-5 Volts
APP Sensor 2? ? ? ? ? ? ? ? ? ?0-5 volts
APP Sensor 1? ? ? ? ? ? ? ? ? ?0-100%
APP Sensor 2? ? ? ? ? ? ? ? ? ?0-100%
APP Sensor 1 & 2? ? ? ? ? ? ?Agree/Disagree

I think what you want to attack is the TAC module, not the PCM.......

BTW, as an afterthought... a simple 0-5V pid built in HP Tuners and delivered via one of the analog input channels on the MPVII will easily read throttle position from the TAC module.... :wave:

dhrivnak · Dec 26, 2007

FlaBouy said:
....
I think what you want to attack is the TAC module, not the PCM.......

BTW, as an afterthought... a simple 0-5V pid built in HP Tuners and delivered via one of the analog input channels on the MPVII will easily read throttle position from the TAC module....

I am showing my ignorance here. How do you access the TAC? Is it throught he OBD 2 port as well? The more I learn the more I realize I need to know.

FlaBouy · Dec 26, 2007

dhrivnak said:
I am showing my ignorance here.? How do you access the TAC?? Is it throught he OBD 2 port as well?? The more I learn the more I realize I need to know.

The TAC module is not "accessed" but one can piggyback/intercede its signals. It is a simple rudimentary dual channel analog device that takes accelerator pedal position (0-5 volts) and outputs a 0-12 volt signal to the throttle plate. Both pedal and throttle plate have redundant position sensors that close the loop back to the module for sensing correct position....

Since the HP Tuners MPVII interface can accept analog inputs and control analog outputs, it is a simple matter of capturing/controlling this circuit. I can also very easily program a Microchip PIC controller to do the very same thing.

EDIT:

Page 348

Page 352 shows an illustration and I can provide specific terminals per my 2004 GM Service Manual :wave:

FlaBouy · Dec 26, 2007

Accelerator Pedal Position Connector

Pin Wire Color Circuit Number Function
A GRY 1273 LOW REFERENCE
B PPL 1272 LOW REFERENCE
C LT BLU 1162 APP SENSOR 2 SIGNAL
D TAN 1274 5 VOLT REFERENCE
E BRN 1271 LOW REFERENCE
F DK BLU 1161 APP SENSOR 1 SIGNAL
G WHT/BLK 1164 5 VOLT REFERENCE
H
J YEL/BLK 1275 5 VOLT REFERENCE
K DK GRN 1163 APP SENSOR 3 SIGNAL

CONNECTOR PART NUMBER: 15318071

FlaBouy · Dec 26, 2007

TAC MODULE CONNECTOR C1

Pin? ? ? ? ?Wire Color? ? ? ? ? ?Circuit Number? ? ? ? ?Function
1? ? ? ? ? ? DK GRN? ? ? ? ? ? ? ? 485? ? ? ? ? ? ? ? ? ? ? ? ?TP SENSOR 1 SIGNAL
2? ? ? ? ? ? GRY? ? ? ? ? ? ? ? ? ? ? 416? ? ? ? ? ? ? ? ? ? ? ? ?5 VOLT REFERENCE
3? ? ? ? ? ? BLK? ? ? ? ? ? ? ? ? ? ? 452? ? ? ? ? ? ? ? ? ? ? ? ?LOW REFERENCE
4? ? ? ? ? ? DK BLU? ? ? ? ? ? ? ? ?84? ? ? ? ? ? ? ? ? ? ? ? ? ?CRUISE CONT SET/COAST
5? ? ? ? ? ? GRY/BLK? ? ? ? ? ? ? ?87? ? ? ? ? ? ? ? ? ? ? ? ? ?CRUISE RESUME/ACCEL
6? ? ? ? ? ? LT BLU? ? ? ? ? ? ? ? ? 1320? ? ? ? ? ? ? ? ? ? ? CHMSL SUPPLY VOLTAGE
7? ? ? ? ? ? PNK? ? ? ? ? ? ? ? ? ? ? 1339? ? ? ? ? ? ? ? ? ? ? IGNITION 1 VOLTAGE
8? ? ? ? ? ? BRN? ? ? ? ? ? ? ? ? ? ? ?582? ? ? ? ? ? ? ? ? ? ? ?TAC MOTOR CONTROL - 2
9? ? ? ? ? ? LT BLU/BLK? ? ? ? ? 1688? ? ? ? ? ? ? ? ? ? ? ?5 VOLT REFERENCE
10? ? ? ? ? BLK/WHT? ? ? ? ? ? ?1704? ? ? ? ? ? ? ? ? ? ? ?LOW REFERENCE
11? ? ? ? ? PPL? ? ? ? ? ? ? ? ? ? ? 486? ? ? ? ? ? ? ? ? ? ? ? TP SENSOR 2 SIGNAL
12? ? ? ? ? ORN/BLK? ? ? ? ? ? ? 1061? ? ? ? ? ? ? ? ? ? ? ?UART SERIAL DATA
13? ? ? ? ? DK BLU/WHT? ? ? ? ?774? ? ? ? ? ? ? ? ? ? ? ? UART SERIAL DATA
14? ? ? ? ? GRY? ? ? ? ? ? ? ? ? ? ? 397? ? ? ? ? ? ? ? ? ? ? ? ?CRUISE CONT ON SW
15? ? ? ? ? BLK? ? ? ? ? ? ? ? ? ? ? 550? ? ? ? ? ? ? ? ? ? ? ? ?GROUND
16? ? ? ? ? YEL? ? ? ? ? ? ? ? ? ? ? 581? ? ? ? ? ? ? ? ? ? ? ? ?TAC MOTOR CONTROL -1

CONNECTOR PART #: 12191065

I will post connector 2 in a bit as well as the PCM to TAC interface and Throttle body connector if needed

FlaBouy · Dec 26, 2007

TAC MODULE ONNECTOR C2
Pin Wire Color Circuit Number Function
A GRY 1273 LOW REFERENCE
B PPL 1272 LOW REFERENCE
C LT BLU 1162 APP SENSOR 2 SIGNAL
D TAN 1274 5 VOLT REFERENCE
E YEL/BLK 1275 5 VOLT REFERENCE
F DK BLU 1161 APP SENSOR 1 SIGNAL
G WHT/BLK 1164 5 VOLT REFERENCE
H
J YEL/BLK 1275 5 VOLT REFERENCE
K DK GRN 1163 APP SENSOR 3 SIGNAL

LOOK FAMILIAR? Other than pin E you are looking at a direct wire from the Pedal position sensor connector

Connector Part # : 12177091

FlaBouy · Dec 26, 2007

Throttle Body Connector

Pin Wire Color Circuit Number Function
A YEL 581 TAC MOTOR CONTROL -1
B BLK/WHT 1704 LOW REFERENCE
C BRN 582 TAC MOTOR CONTROL - 2
D BLK 452 LOW REFERENCE
E LT BLU/BLK 1688 5 VOLT REFERENCE
F PPL 486 TP SENSOR 2 SIGNAL
G DK GRN 485 TP SENSOR 1 SIGNAL
H GRY 416 5 VOLT REFERENCE

CONNECTOR PART # : 15326836

FlaBouy · Dec 26, 2007

So to sum all this up, the TAC Module recieves 2 seperate 0-5 volt references from the pedal position sensors (redundant backups) on connector #2 Pins C and Pins F. It compares the two to make sure they agree and uses it to determine output to the Throttle plate....

So using either of those 5 volt references for throttle position is easy to track.....

GT · Dec 26, 2007

I think this kit utilizes an interface module that taps into the OBD2 databus. It monitors specific PIDs. Doesn't sound like it has provision for analog inputs.