Submitted by: "Louis A. Mendes" (lmendes at direct.ca)
OK Guys and Gals, here's the promised circuits for the TCC Lock and Release Circuits, with lights... The explanations may seem long to some, but I would like everyone to be able to understand what is happening at each phase, so please bear with me... Firstly, in order to properly fill in the gaps on the TCC circuit, there are two separate portions to the control of the TCC... (a) Part 1 -- the ECM controlled portion that locks the TCC *Normally open until the ECM closes it. (b) Part 2 -- the ECM controlled portion that works in conjunction with the brake pedal, cruise control, and engine vacuum functions to disengage the TCC. *Normally closed until opened by the brake pedal. As such, there must be two separate switches; one for each portion of the control from the ECM to the TCC locking solenoid and unlocking circuit. PART 1 --- Frank S.'s original thread and George D.'s repeat of such thread about the TCC Lock circuit is 100% correct; the ECM would normally ground the TCC Solenoid at a given speed (controlled by the ECM) to lock the TCC... By bypassing the ECM to TCC Solenoid circuit with a simple SPST switch between pin 'F' on the Assembly Line Data Link (ALDL) connector and 'Ground' tricks the TCC solenoid into locking at an earlier stage... To verify the correct wire, in case the terminal connection cannot be identified, then look for a TAN wire with a WHITE stripe within the ALDL wire harness... Tan/White Wire ------->[switch ] [switch ]----------->to ground [end #1] [end #2] When the switch is OPEN, the circuit will function under NORMAL ECM controlled function; when the switch is CLOSED, the TCC is ENABLED. If you want to add a light to tell you when the TCC is Locked, the simplest manner to connect a load circuitis as follows... Tan/White Wire ----->[switch ] [switch ]-----------> to ground [end #1] [end #2] | | [SPST ] ------------->[12V lamp]----->to +12 V [RELAY] In this way, when then TCC Locks, the entire circuit will "clamp" to Ground, thus completing the connection through lamp circuit. Until the TCC locks, the lamp will not be lighted. PART 2 --- As Don Bryer, brought up in his thread up a possible DISABLE function, he was right in that the lead from the back of the brake pedal would work in disengaging the TCC from locking. This is the reason that by pressing down on the brake pedal disengages the cruise control function, and also starts a 20 second delay that unlocks the TCC solenoid in the process... In order to keep the TCC unlocked (for towing, etc. as mentioned in Don's thread), your would connect a simple SPST switch on the PURPLE lead that exits the switch on the back of the brake pedal... this lead is the ECM Breaking Switch... So, the switch could be setup as follows: Purple Wire ------->[switch ] [switch ]----------->Purple Wire [end #1] [end #2] This switch tricks the ECM into thinking that the Brake pedal has been pushed down, thus disengaging the TCC in locked mode, or from going into locked mode. So, when the switch is OPEN, the TCC will unlock; when it is closed, it is under NORMAL conditions.