Ok im trying with the help of member to solve my hesitation issue.So i ve done a couple of logs with datamster.My speedometer was working fine.

I had a dtc code 42 and 51.I clear the code and reflash the pcm with my madz28 tune.Now my speedometer is way too low compare to the real speed that im running.I ve install a new pcm with my tune and it still the same.

I made a WOT run in 4th gear to 6500 rpm and at 6400-6500 rpm my speedometer is showing me around 49-50 mph witch is way to low...I was way over the 100mph mark before.

I also change my vss(vehicule speed sensors) and it didnt change a iota.


So what should i check???

Thanks

 

Sounds like the PCM is programmed for a 40-tooth A4 VSS reluctor, but your T56 has the standard 18-tooth reluctor.

 

I thot it was a 17 tooth reluctor on the manual?

 

just so you know I had the same roughly 1/2 MPH issue myself one day, I never installed anybody elses tune, just my own. I reverted back to when I knew the tune was OK and it fixed it, I then applied the changes to that tune and things have been fine since, my changes never were speedo related except the very first tune I loaded, but that was about 50-75 tunes before I had the problem.

Apparently the Speedo settings are touchy and can get corrupt easily.

 

So changing to a 18 tooth reluctor in the program will solve the problem.

Stupid question:In Tunercat where and how do i do it?

By the way Fred i ve order some o2 sensors(ac delco) since you thougt mine are not heating up.

 

It's very easy in Tunercat. Click on "tools" in the upper tool bar. Then click "speed cailbration". Once that window opens it will be self explanatory.

 

So everything was set correctly... i think:

-TIRE SIZE :285-35r18
-Gear Info: 4.11.1
-Car Type: F or B car
-Trans Type: manual
-Stock speed sensors

This give me 17 driveshaft pulse and dont ask me how but the current calibration got 40 drivesahfat pulse.

So the diagnosis was perfect.I ve change it and i try it later.

Thanks

 

Make sure the 'Automatic Trans. Option' is unchecked in the ECM Switch Table.