Brake Signal / TCC Ground, and Park Neutral Signal into PCM.

[paradigm]

My PSI harness has two wires not connected from the LS PCM to the '86 Monte Carlo that I have a 5.3 LS in:

PURPLE - Brake Signal / TCC Ground. Signal into PCM to let the PCM know when brakes are applied, to control Torque Converter Lockup and Cruise Control. - This would go to the brake switch on the car, to provide 12V when brakes are not engaged and 0V when brakes are depressed.

ORANGE - Park Neutral Signal into PCM (NOT NEUTRAL SAFETY); Lets your LS PCM know you are in Park and/or Neutral so it can use appropriate Timing tables, and crank relearn can be performed) - Where on the Gbody would I connect this to?

Car is an 86 Monte Carlo SS with a 5.3 LS, PSI conversions wiring harness, and a 700R4 mechanical transmission.

Thanks

 

[paradigm]

I looked by the brake pedal and only found this switch:
None of the exposed leads tested 12V with the key on. Where else can I grab the brake switch 12V when the brakes are not applied and 0V when the brakes are depressed?

Also this wiring harness has the pink wire hot when key is on, but nothing on the purple wire. Where would this have been plugged into?

 

[pagrunt]

Also this wiring harness has the pink wire hot when key is on, but nothing on the purple wire. Where would this have been plugged into?

That would of been plugged into the brake switch at the two bare terminals. It's for the CCC to allow the lock up converter to lock/unlock.

 

[paradigm]

That would of been plugged into the brake switch at the two bare terminals. It's for the CCC to allow the lock up converter to lock/unlock.

The strange thing is that the two bare terminals on the brake switch do not line up with this harness.

 

[ELCAM]

Does it look like it would plug into this?

 

[paradigm]

Does it look like it would plug into this?

Is this a different style of brake switch?

The harness with the pink / purple TCC wire has it's female ends spread a little wider than the male pins on the brake switch. It could be that the prior owner swapped out the brake switch for a different one.

Anyhow I plugged the pink wire / hot lead from the harness onto the brake switch and tested the other pin with a multi meter. It gives 12V when the brakes are not engaged and 0V when the brake is engaged, so this is where I will pickup the TCC wire from.

Now I need to figure out how to get the Park Neutral signal into the LS PCM? The transmission is a mechanical 700R4 so is there even a provision from this? Could it come from a switch on the steering column?

 

[ELCAM]

That's a second brake switch for the cruise control. You can see the hole above your existing switch where it installs.

The two terminals on your existing switch are the ones you want to use as you found out. Just grab power from somewhere and run the other wire back to the computer.
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There should a pair of unused terminals on the backup light/neutral safety switch. The terminals being used are for the back up lights. Same deal grab some power for one terminal and the other goes to your computer. This switch is at the bottom of the steering column.

 

[pagrunt]

Is this a different style of brake switch?

The harness with the pink / purple TCC wire has it's female ends spread a little wider than the male pins on the brake switch. It could be that the prior owner swapped out the brake switch for a different one.

Anyhow I plugged the pink wire / hot lead from the harness onto the brake switch and tested the other pin with a multi meter. It gives 12V when the brakes are not engaged and 0V when the brake is engaged, so this is where I will pickup the TCC wire from.

Now I need to figure out how to get the Park Neutral signal into the LS PCM? The transmission is a mechanical 700R4 so is there even a provision from this? Could it come from a switch on the steering column?

Possible the brake light/TCC switch was changed after everything was pulled but my '86 had that connector that plugged into the switch. There is a pair of terminals on the gear selector/back up/neutral switch on the column that should work. An orange/black stripe wire runs from the ECM to the one blade for the Park/Neutral Input, circuit 434 & a black/white stripe wire for the ground, circuit 450. The switch is closed when it's in the Park & Neutral positions.

 

[paradigm]

Possible the brake light/TCC switch was changed after everything was pulled but my '86 had that connector that plugged into the switch. There is a pair of terminals on the gear selector/back up/neutral switch on the column that should work. An orange/black stripe wire runs from the ECM to the one blade for the Park/Neutral Input, circuit 434 & a black/white stripe wire for the ground, circuit 450. The switch is closed when it's in the Park & Neutral positions.

I will try the harness again on that TCC switch to see if I can get it to fit. Worst case Ill just make my own harness.

The PSI harness orange wire for park neutral signal needs a ground from the car's park neutral switch. Would that come from the orange/black stripe wire or from the black/white stripe wire?

Where are you getting the circuit numbers from? I have a soft copy of the factory service manual but I am not able to locate the circuits in it.

 

[pagrunt]

I will try the harness again on that TCC switch to see if I can get it to fit. Worst case Ill just make my own harness.

The PSI harness orange wire for park neutral signal needs a ground from the car's park neutral switch. Would that come from the orange/black stripe wire or from the black/white stripe wire?

Where are you getting the circuit numbers from? I have a soft copy of the factory service manual but I am not able to locate the circuits in it.

The black/white stripe is the ground & the orange/black stripe is "hot"/signal feed. As for the circuit numbers, I have a collection of electrial manuals for '78-'88 & get them from the diagrams or in some the list of circuit numbers & names. This makes things easier for cross checking changes in harnesses & components.