speedometer reads double and gas gauge reads backwards

[pontiacjeff]

2008 LS4 in a 2002 Pontiac Montana.

Scanner shows ECM speed output same as speedo, exactly double. So its not an instrument error.

Not too much differemt bt 2002 and 2008. I wouldnt have expected this issue, of all things that could have gone wrong!

Everthing else is flawless. I turned off DoD for now til the speedo issue is fixed bc it was freaking out.

Any help is greatly appreciated. I was going to post screenshot of speedo but can't on mobile.

[schpenxel]

Do you have both tunes?

Log all of the fuel tank level stuff you can find to see what's going on. If those and the gauge match then it's probably a tune issue and not anything wrong with the cluster.

There should be a table or two in the fuel system-->fuel tank tab that defines fuel level resistance to fuel level volume. Might have to basically reverse that table. Primary level volume and primary level volume gauge

[pontiacjeff]

Yay! Didnt realize the calibration for the gas gauge was so involved. Entered my new capacity, scaled it backwards, and the gauge works correctly now. Thanks for the tip!

Now, for the speedometer.

[pontiacjeff]

All the values in speedometer calibration are correct for gear ratio, tire rev/mile (I always measure actual tire roll-out and calculate). The vss is set to RepTOS. I changed to serial, nothing happened. Changed avg pulses from 4 to 8, nothing happened. I measured w GPS speedometer on my phone, the speed is reading just a tick under double. 70 = 36, 80 = 42.

[Jon S.]

When you get a chance post the original 2002 tune, and the 2008 tune that you are working with

[pontiacjeff]

2002 chevy venture awd 3.4 os:12223488

2008 Grand Prix GXP LS4 5.3 E67 os: 12618164

[pontiacjeff]

I dont have my 2002 van in hp. But I do have a 2004. The numbers in the speedo calibration make absolutely no sense.

Hardware
Vss p/rev - trans = 9.1055

Gear ratio & tire size
Drive sprocket ratio 1.000:1
Trans revs/mile 2,608.82

Sensor calibration
Vss pulses per mile 23,220

The 2008 tune is currently:

Hardware
Vss pulses per rev 30.000
Iss pulses per rev 25
Vss pulses per rev - trans 30.000

Veh speed sensor
veh speed output RepTOS
Pulse avg 4
Max period 300
Serial min freq 1hz

Wheel speed output disabled

Gear ratio & tire size
Final drive ratio
Ratio. 3.29
Ratio error 3.29
Trans. 3.29
Trans error 3.29

Sensor calibration
Vss tire revs per mile
Dist. 746.99 (actual tire roll-out calc by me)
Dist err. 746.99
Dist trans 746.99
Dist T err. 746.99

The weird thing is, when I pulled up the stock file in the gear/tire calculator, it had a tire diameter of 52.45 and short shifted, 2-3-4, boom boom boom. By like 20mph (40 on speedo). I changed it to my 27" tall tire and auto scaled and the trans shifts fine now (mostly) but the speed is still double.

[Jon S.]

OK .. so you are now using an E67 and a T42 ? You have been asked twice, by two different members, to post your tunes - if you actually want any help. Guessing that the problem is a vehicle speed comms issue between the T42 and the E67.

[pontiacjeff]

Post my tunes? Are you asking for the .hpt file? I have to do that from my laptop. Can't do it from my smartphone. I will try to upload it tonight.

[pontiacjeff]

Here is my latest tune.

[Jon S.]

If the Speedometer indicates twice the actual speed, try changing "VSS Tire Revs per Distance" (ECM 9003) from 747 to 1494. Only change this parameter. Do not use the Wizard, nor change anything else.

If the shift behavior remains OK (the same as it is), and the speedometer is close, then fine tune the speedometer by changing ECM 9003 by the percent error.

[pontiacjeff]

Cool. Thanks man! Ill let you know.

[pontiacjeff]

That did it... Ain't even gonna spend one second wondering why. Lol! Thanks for the tip. I really appreciate it.