Re: TCC unlock tables?
You're looking at the logic of F42/F43 wrong. The two tables work independent of each other based on the same basic data. The upper table is used if the TCC is currently locked and contains values to determine at what point (TPS vs MPH) the TCC will unlock. Likewise, the lower table is used when the TCC is unlocked and contains values to determine at what point lockup should occur (again, based on TPS vs MPH).
These are functional as long as all the minimum criteria have been met.....including (but not limited to):
- Coolant Temp
- Minimum Run Time
- TPS Unlock Delta (relative to negative/positive criteria).
- Road Speed Coast Level
- Road Speed Upper/Lower limits (discussed below)
- Etc...
The 5 things you'll adjust the most will be:
- Minimum Coolant Temp
- F42
- F43
- KRSHNTLK (lower)
- KRSHNTHK (upper)
KRSHNTHK/LK operate with a hysteresis in mind. Say the lower value is set to 38 and the upper is set to 40. In this example, the TCC will remain unlocked until 40 mph, at which point it will lock (assuming other criteria met) and remain locked until the MPH falls to 38 or lower (again, assuming all criteria met). If we were to set the two values the same (say, 40 mph), then you would have the ECM trying to lock and unlock the TCC at 40 mph, resulting in chatter (and eventually some premature failure if you drove at 40 too much). This is the reason for the hysteresis built in by commanding different road speed values for these 2 constants. General rule of thumb is to keep the lower at least 2-3 mph under the upper.
HTHs