Rex4Life

I saw some threads talking about this 20K switch but did not definitively answer my question. I don't want to burn up my ECU so here's the question.

Can I ground the L/B wire (F-31 connector) from ECU pin 1O and simulate over 20k mileage to the ECU?

This is for an 1988 Turbo II ECU (N333). I've installed the engine and ECU system into my 84 GSL-SE and that car is not equipped with a 20k switch. Installing the gauge unit is not an option. Currently during my engine break-in I've got the wire disconnected and taped off (the engine is running good and I can't wait to really open it up a bit).

The T2 original cluster gauge unit has about 2.8 ohms thru the switch which isn't much of a load. It looks like to me that the ECU has an internal load on this circuit and just grounding the wire should simulate over 20k miles and not burn up the ECU.

If the switch did supply the load (all 2.8 ohms of it) then the ECU would still see the 12 volts so it doesn't look like this 2.8 ohms is the load on this circuit.

Thanks in advance for your help.

Scott

(edit...remove enormous signature...check your PMs)

SureShot

Hmm - The FSM wiring chart shows the 20K switch as just an open/close contact that closes after 20K.

I never quite understood why it opens at 100K & closes again at 120K, then again at 200K

Bukwild

sweet first gen. Man that will be a fast car. I was going to drop a street ported t2 with a t04b on one before I swapped my vert. Nice job total sleeper

HAILERS

The only thing I know of that it controls is the PORT AIR solenoid. After twenty grand that solenoid isn't energized anymore.............til 100,000 comes up then it's energized for the next twenty grand. Been there, seen that. Obviously there might be more going on here than the Port Air Solenoid.

Rex4Life

I really need to know if it's ok to ground out that wire?

HAILERS

By the power vested in me......I now grant you permission to ground that wire. You must do it this day. After midnight the permission is withdrawn and you will have to wait another thirty days for permission to do it again, all depending on what mood I'm in at that point in time.

In other words.....your ground or the combination meters ground.....one and the same thing. Go get 'em.

Rex4Life

Cool, thanks HAILERS--ehh but I gotta wait for engine break-in first--guess I'll have to wait 30 days--oh well.

Yea I thought it was ok, just wanted some confirmation, ya know about taking a 12v wire and grounding it.

thanks again,

Scott

p.s. oh yea, look like I got busted on my sig. No big deal already fixed.

rxspeed87

just curious whats with this 20k mile ground biz?


my car just passed 200k so is there something with that ground point that I am going to deal with once again?


but what all does it do?

SureShot

HAILERS mentioned the port air solenoid.
Other than that, it looks like an early idea in design whose function later became unneeded.

I grounded mine theorizing if might be holding off my Aux ports & VDI, but that was wrong.
It turned out to be a bad neutral switch connection.

Hot_Dog

The 20K miles switch is only active during the first 20K miles of the car's life. It does not reactivate again after 100K, 200K, 300K miles and so on. The 20K mileage switch will recycle after the odometer turns past the 999,999.9 mile mark. It's unlikely that such an event will ever occur.

Hot_Dog
90 RX7 GXL
02 Acura RSX-S

Amur_

https://www.rx7club.com/showthread.p...threadid=78717

HAILERS

*********The 20K miles switch is only active during the first 20K miles of the car's life. It does not reactivate again after 100K, 200K, 300K miles and so on. The 20K mileage switch will recycle after the odometer turns past the 999,999.9 mile mark. It's unlikely that such an event will ever occur.

Hot_Dog
90 RX7 GXL
02 Acura RSX-************88

No, it works just like that. I've got the living proof out there in my driveway. 212,000 miles and the PortAir solenoid is energized. The other car at some obscene figure 144,000 miles and no Port Air activation and the third one at 184,000 and no Port Air activation.

I don't know who started this idea about the 20,000 mile reactivating, but I was a doubter til I looked at my odometer last year and whoa, its true.

I'm anxiously waiting for the next eight grand to turn over on the first vehicle. If there is not a change I'll be sure to say so on this site.

It ain't unlikely. It's so.

HAILERS

****my car just passed 200k so is there something with that ground point that I am going to deal with once again?****

No is the answer. BUT it would be interesting if you went out to your car and pulled your PortAir solenoid out and turn the engine on and see if the solenoid pulls the poppet valve *in* or not. It's just an emission thing. That PortAir passage is quite small. Adds extra airpump air to the exaust ports. Not much.

theloudroom

The port air solenoid and the 20,000 mile switch are SEPERATE wires. They run to seperate pins on the ECU .

rxspeed87

what is the port air solenoid and where is it?


or is that the thing in the ACV?

anyway to check if it is working without taking it off?

HAILERS

Two solenoids on the acv. The fwd one is the PortAirSolenoid. The aft one is the SplitAirSolenoid.

There is 12v on the black/white wire all day long as long *** the key is to ON. What triggers the solenoid is the other wire. It puts a ground on the solenoid from the ECU. That will pull the 12v down to waaay low like 1-2volts. So if you back probe the other wire with everything connected up...you should read 12v if the odometer reads over 20,000 miles but about 1-2volts from 0-20,000 miles.

BAck probe means finding the connector and shoving the probe (or a piece of wire attached to the probe) thru the backside of the connector. Put the negative lead of the meter on any good chassis ground or engine block/whatever.

And the other solenoid, the SplitAirSolenoid, will have 12v all day long UNTIL you put the car in ffith gear, whereupon it drops to 1-2volts. In fifth it opens the SplitAirSolenoid to add air to the Split Air Pipe for the catalytic converter. You don't need to start the engine to see that happen. Just have the key to ON.

NZConvertible

Nobody said they weren't seperate. The 20,000 mile switch sends a signal to the ECU, and the ECU opens the port air solenoid.

SureShot

When I saw the 20K switch was a seperate 5 wheel odometer, I just jumpered it closed.

No worries..

HAILERS

*****The port air solenoid and the 20,000 mile switch are SEPERATE wires. They run to seperate pins on the ECU .******

See the NZ explanation above. It's no different than engaging fifth gear which in turn triggers the SplitAir solenoid being energized thru the ECU. Or the signal from the TPS triggering a ground on the Switching or Relief solenoid thru the ECU.

Hot_Dog

To my best recollection, the 20K mile switch was a 6-wheel odometer, which is identical to the main odometer.

Hot_Dog
90 RX7 GXL
02 Acura RSX-S

theloudroom

My point was the the port air solenoid and 20k mile switch are both controlled by the ECU, and unless you're further along reverse engineering the ECU than me, you shouldn't be checking to port air solenoid to see if the 20,000 mile swich is closed.

If you've got a car with 212,000 miles on it in your driveway, go measure the 20k mile switch.

HAILERS

No. That's not right. The ECU is NOT controlling the 20,000 switch. The twenty grand switch, when it switches over twenty grand, puts a ground ON the ECU pin. The ECU then stops putting a ground on the Port Air Solenoid.

It's similar to the fifth gear switch. You put the transmission in fifth gear, which in turn puts a ground on the ECU. The ECU sees the ground and then puts a ground on the Split Air Solenoid.

Oh, the pin 1O with the 212,000 miles shows open with the plug disconnected and with the plug connected shows 12v (no ground results in no voltage drop).

The cars with over 220,000 miles shows .350 something volts because of the ground being put on the wire by the 20,000 mile switch.

The 20,000 mile switch is NOT controlled by the ECU. Its nothing different that the water temp switch at the bottom of a series four radiator having open contacts until the water reaches a certain temp whereupon it puts a ground on pin 1H, which tells the ECU that the water is up to temp now, so you can now put a ground on the Relief Solenoid and close off the dumping of the airpump air at the ACV.

The Port Air Solenoid IS controlled by the ECU and the ECU knows when to close the port air solenoid by the twenty grand switch TELLING THE ECU that its now past twenty grand (by putting a ground on pin 1O).

There's nothing high tech about it. Just a ground at twenty grand and above (until you hit 100,000.1 miles, that is.

theloudroom

Of course the 20k mile switch is a sensor, not an actuator.

My point was the unless you've reverse engineered the ECU, the connection betwen the port air soleniod and the 20k mile switch is a debatable topic in itself.

Maybe the ecu just reads the 20 mile switch and toggles the actuator, 1:1 or maybe it does something more complex. We don't know, so if you want to prove something you should measure the switch itself, not the solenoid.


The only way the 20,000 mile switch interacts with anything else in the car it through the ECU.

NZConvertible

The 20K mile switch is an ECU input; the port air solenoid is an ECU output. The ECU can't "control" switches.
You don't need to have reverse-engineered the ECU to be able to read and understand the FSM. Go look at the table on page F1-77 or F2-75 of the S5 FSM where it quite clearly explains how the 20K mile switch affects the operation of the port air solenoid.

theloudroom

You guys should have been able to obviously see what I meant.


This whole debate is because people won't believe the FSM in the first place. The 88 FSM states that the 20k miles switch is trigged above 20,000 miles, PERIOD. It states nothing about 100,000-120,000 miles, etc.