safc causing check engine light

[96 420a-t]

As stated above I installed my SAFC I last night. Works great got the tune dialed in... almost.

But anyways my CEL keeps coming on giving me a p1296. Anyone have any experience with this problem? Maybe a cure. Any help is appreciated.

Edit: mods list is up to date.

 

[TsiJohn333]

Try checking your map sensor. P1296 means No 5 Volts to MAP Sensor. Try going on that route and replacing it and see if the code comes on again.

 

[96TurboGS]

Seems like this only happens to 96'; It happened to me in the past.

The PCM is checking the voltage for ~5v (Atmospheric pressure) several seconds after you turn the key to off. Because you have the SAFC installed, when you turn the key off this in turn opens the circuit and blocks the signal voltage from the map sensor to the PCM. So if you really need to fix it you could install something like a 555 timer circuit or a small IC with a relay connected to the SAFC to act as an "off delay". (Overkill but will keep the light off, normally) However, your zener diode mod may still give you a DTC flag if it's clamping too much voltage, but it should work fine.

If you're using a 12:1 regulator, you don't need a SAFC.

 

[96 420a-t]

Its a brand new sensor, I have to run a safc because I'm running larger injectors.

 

[96TurboGS]

You should be able to handle 275cc (in profile) just fine without one. If you have a constant 5v coming in on the Vref and a output of 4.5v or above with the key "on" then you have the problem I mentioned.

 

[96 420a-t]

That makes sense, I don't understand how to wire it up so it stays on. Any links or anything you can point me in the right direction?

Edit; the main reason I'm running the 275cc's is because I was running lean at about 4psi. So the safc let me choke back the injectors at idle. Fuel trims hover right around 0% at idle and stays rich all the time.

Edit #2: the zener diode is a 4.3v. Under boost my ecu sees 4.5v max. It only happened after the safc install. So I need to keep the safc on for a bit after I shut the car off.

 

[96TurboGS]

I think I used an IC from a digital gauge I built some time ago, but come to think about it, you can use just a relay to trigger the AFC. Connect a relay to AFC (VOUT) and BATT (VIN). Use the 5vref wire to switch on and off the SAFC. (Positive input switch) Make sure you don't hook up the output of 12v to the vref!! You should bench test this before putting it in the car. That way it will stay on long enough after the key is turned off and will turn on whenever you turn the key.

Here is something i pulled off google to get you started, should be easy.