FICM recal / speedo recal
 

I have an 04 CC LB dually 72K miles that I just put a new to me 06 FICM ($300) in today. What a relief, that alone brought my mileage up 4 mpg, at least on the lieO meter. The new FICM holds 48.5v all day long although it does have the FICM killer program in it, but not for long. I want to have my OEM FICM retuned then mate it up with the good power supply and reinstall it.

My question is which ECM holds the speedo cal? I have 245x70x19.5 tires that are 33" so I had to have one of the ECM's recalibrated but I don't know which one holds that info? It still seems to be shifting correctly so I am assuming its not in the FICM. I should have brought my GPS with me today that would verify that the speedo is correct.

Mike

Mike,

You are correct the FICM only controls fuel injection. The PCM controls the speedo(located next to the drivers side battery).

Thanks that's what I was thinking.

Speedometer is actually calibrated in the ABS module, this is why most tuners can't change it. If it was in the PCM it would be easy. Auto Enginuity can access and reprogram the values in the ABS module.