Baseline for 7.4l Vortec long block w/TBI induction?

**Casey** · 12-23-2023

Right, it's a '95 TB with '87 injectors.

**1project2many** · 12-23-2023

The last two digits of the BCC code is how late the revision is. For example AA would precede BB

I would not use this logic when looking at calibrations. Calibrations can be released that solve specific issues in certain vehicles but are not appropriate for most vehicles.

I have been told that the van tunes are detuned somewhat I have never actually looked at them myself to see but I've always used the truck tunes

Sometimes van calibrations have some reduced timing values and sometimes the transmission calibrations are milder. I agree with using truck calibrations in trucks.

In '95 it went BMHM->BPRK->CAJR,

BMHM is the initial calibration.
BPRK was released to eliminate code 32 setting under heavy load. See TSB 57-65-09.
CAJR was released to resolve No Upshift/2Nd Gear Only After Cold Start-Intermittent DTC 87-High Ratio Error. See TSB 67-71-53A

It looks like BJKX would be the latest, and is for a truck so I'll start there.

That's a leaded fuel compatible calibration. At a minimum closed loop needs to be enabled. Other related functions may not be correctly calibrated.

16198042, 8055, BJKX N/A -
ECU: 16196395 MODULE, PCM (REMANUFACTURED) *** S/S BY 16197427
Transmission : MT1 AUTO 4 SPD THM R2 (4L80);
Emission System : NM8 EMISSION SYSTEM, LEADED FUEL;