How does A4 pcm determine its in P/N or in gear exactly?

[GrannySShifting]

Figuring out a way to indicate to pcm on a 4l80e or th400 swapped Camaro/Firebird that it is in or out of gear for gnarly cammed stuff. I had figured this out years ago (@07) and for the life of me cant remember what I did. Officially old now

Its going to take the use of nuetral safety switch circuit, and then using that feed to trigger a relay I believe to make/break contact of the circuit it references to tell it what base IAC table to choose from

[GrannySShifting]

No one knows?

[matty b]

If you are using a 4l60e or a 4l80e, there is an internal pressure switch that indicates the gear. It will not work unless the motor is running as you wont have any line pressure. This is the Transmission Range Swtich and it looks like this



The park neutral switch, which controls the starter, reverse, gear indicator is the one that bolts to the selector shaft

[68Camaro]

the th400 - you can use the neutral safety switch on your shifter and supply 12v to pin 34 of the blue PCM connector. In the tune file under system set the PRNDL setting to P/N only. This will allow you set up your base running airflow table for park/neutral and in gear. hope this is what you are looking for

if using the 4l80 and are not using a PRNDL switch you can set the system parameter to - none - and the pcm will use the internal pressure switch for indicated gear(as long as it is still being controlled by the PCM and not a manual valvebody deal). If it is a manual valvebody 4l80 then just set it up like the th400 deal

[GrannySShifting]

the th400 - you can use the neutral safety switch on your shifter and supply 12v to pin 34 of the blue PCM connector. In the tune file under system set the PRNDL setting to P/N only. This will allow you set up your base running airflow table for park/neutral and in gear. hope this is what you are looking for

if using the 4l80 and are not using a PRNDL switch you can set the system parameter to - none - and the pcm will use the internal pressure switch for indicated gear(as long as it is still being controlled by the PCM and not a manual valvebody deal). If it is a manual valvebody 4l80 then just set it up like the th400 deal

Are you sure that works? Pretty sure I tried that by applying B+ voltage with car running and did not see change

[Asylumwarp]

Aren't they negative inputs? Think so. You use a relay to convert the neutral safety positive to negative for pin 34..

[matty b]

Yes, the P/N circuit requires ground in park or neutral and no ground in any other position.

[Asylumwarp]

May want to also search for which pin is correct, iirc its like pin 33 and 34 for inputs... or is it 34 and 35.. Check that out also.

[68Camaro]

Aren't they negative inputs? Think so. You use a relay to convert the neutral safety positive to negative for pin 34..

this^

sorry about the confusion and thank you Asylumwarp for the correction

[GrannySShifting]

the th400 - you can use the neutral safety switch on your shifter and supply 12v to pin 34 of the blue PCM connector. In the tune file under system set the PRNDL setting to P/N only. This will allow you set up your base running airflow table for park/neutral and in gear. hope this is what you are looking for

if using the 4l80 and are not using a PRNDL switch you can set the system parameter to - none - and the pcm will use the internal pressure switch for indicated gear(as long as it is still being controlled by the PCM and not a manual valvebody deal). If it is a manual valvebody 4l80 then just set it up like the th400 deal

Heres the issue with that. Unlike the 99-02 cars, that have the option for NONE - PRNDL - PN Only, the only options for this is a PRNDL Equiped tab with enable or disable as your options?

[68Camaro]

what computer are you using? red/blue? can you post up your file?

[GrannySShifting]

what computer are you using? red/blue? can you post up your file?

98 Camaro/Firebird red/blue

[68Camaro]

The 98 ECM is different and has different pinouts than the 99-02 ECM's (97-98 Corvettes and 98 Camaro/Firebirds use this ECM). I believe the correct pin for P/N on this PCM is 32 red

[GrannySShifting]

So figured this out. Leave the PRNDL setting as stock. Take the C1 #22 Pin (blue wire Trans range B) from the PCM, to the nuetral safety switch on the aftermarket shifter, then from there to ground. Tie in the PCM side of that switch to a relay as its switching ground when it gets grounded will trigger the relay. The blue wire in console for the shifter PN circuit (Blue and white wires that allows the starter to engage) is the switching side power, and split it to the power feed into the relay. The relay output goes to the white wire.

Thinks its in Park or 2nd

[GrannySShifting]

Dragging this up from the dead... similar subject matter

Have 01 truck PCM running a DBC setup with TH400. Not the pain in the ass to figure out 98 stuff i was messing with. ECU blue pin 34 is wired to neetral switch on shifter, then from there to ground, continuity from the ecu pin to ground when the shifter is in park and nuetral only so that wiring is good, PRNDL equipped set to PN only and it STILL doesnt work? Any ideas, OS that doesnt do it properly maybe?

Was looking in trans tab at trans type but Ive set it to 60e, 80e, non electronic trans and none works

[GrannySShifting]

Not sure how this makes sense but I got agitated and figured id try every combination of PRNDL Equiped settings with every combo of Trans Type, 15 combinations later PRNDL set to None (like it had the 60e or 80e internal pressure sensor???) and Non Elec Auto trans type works

Ive only had to set to PN Only and ground the damn blue #34 before