Apexi Safc Install

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Original text: TSN Original Author: Allan, a.k.a. Sprint


So you bought a SAFC, opened the box, looked over the instructions, and found nothing to help you install it into your Saturn S series car, right? Well you've come to the right place. This guide should help you install either SAFC unit into any S series vehicle.

Step one is the installation.

  • For 91 - 99 cars your PCM should be located in the cabin, relatively easy to get to.
  • For the 00-02s however the PCM is located under the hood between the battery and brake booster.

  1. If the display is connected to the wiring harness disconnect it. There's no reason to have the display connected when doing all the wiring.
  2. Disconnect the negative battery cable from your battery. The slightest short while cutting PCM wires can render your PCM worthless and a dead car. Plus for all you 00 - 02 owners you're going want to remove the battery anyway to get good access to your PCM.
  3. Now you need to figure out the wiring for your car.

There were three main wiring schemes based on wiring diagrams available and feedback from others. 
The wiring is broken down between OBDI vehicles 91 - 95, and OBDII vehicles, the two schemes are for 96 - 99 and for 00 - 02.

Wire Color Use for a Saturn

If you look at the SAFC-II wiring harness you will have the following wires. For the SAFC-I simply ignore the purple knock sensor wire:

1 Brown Ground - PCM Side 2 Black Ground - Non PCM Side 3 Red Ignition (B+) 4 Green RPM Signal (Ignition Control CKT) 5 Pink Not Used 6 Orange Not Used 7 Yellow Airflow/Pressure Signal Out to PCM (MAP Sensor) 8 Purple Knock Sensor 9 Blue Not Used 10 White Airflow/Pressure Signal In from Sensor (MAP Sensor) 11 Grey Throttle Signal (TPS Input)

When splicing wires I used the splices supplied. Some people solder their connections or use butt splices. Personally I used what the kit came with and some fancy splicing. For each wire I slowly removed the insulation from about a ¼" piece using an exacto knife. I kind of shaved the insulation off very carefully. When I was done I had a bare spot in the middle of each wire that looked like what you see in Fig-1.

I then took the SAFC wire, laid it parallel to the PCM wire, and spun the bare end around the PCM wiring. I put the crimp connector on and using a wire striper/crimper I smashed it together, as seen in Fig-2:

(Fig-1) Stripped wire
(Fig-2) SAFC Wire crimped onto PCM wire

Then I electrical taped around the splice. If you want you can simple cut the wire in half, splice in your wire, solder it, and tape it up but what I did looked very clean, was very tight, and most importantly worked.

There are two main things to be aware of when wiring this that are also noted in the SAFC manual.

  1. The location of the ground.
    1. You MUST splice the Brown ground wire into your cars ground on the PCM side.
    2. Then move out exactly one inch and splice in the Black ground wire.
      • Do not ground them to the same spot, and do not splice them more then an inch away.
      • You don't need to be completely exact but aim for one inch if you want accurate readings.
  2. The MAP sensor.
    • Use the plugs provided as the SAFC manual shows so if you decide to remove the unit from the loop you can easily reconnect the MAP sensor into the PCM.
    • More on this and other potential pitfalls at the end.

Here's what my ground connections looked like after I taped them both up:

Ground connections

So where do you land all these wires? That's where the vehicles year comes into play.

  • Each group of years PCM is slightly different so reference the table below for your year.
  • Also they have different plugs going into the PCM, though amazingly Saturn used the same colors throughout the years except for the ground on the newer model.

OBDI Saturn Wiring

91-95 OBDI Saturn Wiring
Wire on SAFC 91 Wire on PCM
1 - Brown C-1 (Black/White)
2 - Black C-1 (Black/White)
3 - Red A-7 (Pink)
4 - Green C-11 (White)
5 - Pink Not Used
6 - Orange Not Used
7 - Yellow B-9 (Light Green)
8 - Purple* A-12 (Dark Blue)
9 - Blue Not Used
10 - White B-9 (Light Green)
11 - Gray A-8 (Dark Blue)
Ignore 8 (knock sensor) if wiring a SAFC-I

OBDII Saturn Wiring

96-02 OBDII Saturn Wiring
Wire on SAFC 96 - 99 Saturn 00 - 02 Saturn
1 - Brown J2 - B6 (Black/White) J1 - Pin 73 (Tan/White)
2 - Black J2 - B6 (Black/White) J1 - Pin 73 (Tan/White)
3 - Red J1 - C12 (Pink) J2 - Pin 23 (Pink)
4 - Green J2 - B7 (White) J1 - Pin 46 (White)
5 - Pink Not Used Not Used
6 - Orange Not Used Not Used
7 - Yellow J2 - A7 (Light Green) J1 - Pin 3 (Light Green)
8 - Purple* J3 - C10 (Dark Blue) J1 - Pin 28 (Light Blue)
9 - Blue Not Used Not Used
10 - White J2 - A7 (Light Green) J1 - Pin 3 (Light Green)
11 - Gray J2 - A6 (Dark Blue) J1 - Pin 1 (Dark Blue)
Ignore 8 (knock sensor) if wiring a SAFC-I

  • 97 - 99 PCM:
    • J1-Large Blue
    • J2-Small Blue
    • J3-Large Brown (Manual) or Pink (Auto)
  • 00 - 02 PCM:
    • J1-Large Black
    • J2-Small Black


I'm going to cover setup of both the SAFC I and II in one procedure because honestly there is so much in common with them there's no reason not to. For the most part you will use up and down arrows to change values, left to go back, and right to go forward or select. If you ever are unsure check your manual.

  1. Hook your negative battery cable back up.
  2. Turn your ignition to the on position but DO NOT start your car.
  3. The SAFC should display a nice blue splash screen then list three options: Monitor, Settings, and Etc.
  4. Scroll down to Etc and select it.

ETC Menu

This menu is where we will be setting up the sensor types and configuration information.

  1. Start with the first selection, Sensor Type.
  2. The Saturn's use a pressure sensor so select this option in the list then press next or right.

The next setting will determine how the SAFC reads this pressure sensor. For most cars this will be set to 04 IN / 04 Out.

  1. After setting the pressure sensor press the back button or left a couple times to get back to the etc menu.
  2. Select "Car Select" and next.
  3. For the Cylinder (Cyl) setting use "4" for 91 - 95, "12" for 96 - 99, and "2" for 00 - 02. For all models make sure the arrow points up and to the right.

Now we need to set how the graph will be displayed. In other words how the graph will look compared to the values received.

  1. Press back or left once and look for "Grph Scale" for the SAFC-I or "Disp Scale" for the SAFC-II.
  2. Select it and press next or right.
  3. For Pr (pressure scale) leave it at the default value of 760mmHg.
  4. Ne is the maximum RPM. For our cars this should be set to 7000.
  5. If your Saturn can rev past this then set it to a few hundred past your cars redline.
  6. Next thing to change here is the Cr for correction ratio, which should be set to 30%.

Last thing to change is the VFD brightness.

  1. Press back or left until you are back to the etc menu and select "VFD Bright".
  2. Set the day, dim, and night settings as you see fit. Personally mine are 99, 60, and 15. This is one of the few settings you may need to play with depending on where it's mounted and how easy it is to read for you.
  3. When done press back or left until you're back to the main menu

Settings Menu

The settings menu, strangely enough, contains most of the settings. The first thing to change is the throttle point. This is what tells the SAFC the difference between lo and hi throttle.

  1. Select "TH Point" and press next or right. The two settings are low and high.
  2. Low should be set between 20% and 30%.
  3. High should be set between 60% and 80%.
  4. Start with 25% and 75% and see how those settings work for you first before playing.
  5. Press back or left to get back to the settings menu when done

Next we can set which points in our RPM range to make corrections. Here is where one of the main differences comes into play between the SAFC I and II. The SAFC-I has a total of 8 points; the SAFC-II has 12 that you can adjust.

  1. Select "NE Points" and you will see a list of RPM points.

Since I'm using mine with performance cams, which cause a rich condition and rough idle at lower revs I wanted a closer range on the low side so I could lean it out a little more precisely. Plus my Saturn should never see revolutions over 6500 so I don't need to leave the default of 7000+ in there on the high end. I would suggest starting at 800 on the low side and 6600 on the high for both units, and evening out from there. Just select each point with the right or next then go up and down to raise and lower. The points on my SAFC-II looks like this, giving me a little finer tuning on the low end:

Ne01: 800 Ne02: 1200 Ne03: 1600 Ne04: 2000 Ne05: 2400 Ne06: 3000 Ne07: 3600 Ne08: 4200 Ne09: 4800 Ne10: 5400 Ne11: 6000 Ne12: 6600

Once these are selected press back or left to get back to the settings menu.

The next setting to verify is the Dec.-Air setting. This is used on a hot wire type airflow sensor, which we do not use.

  1. Select with next or right and make sure that "Thr" is set to ****, which means not used.
  2. Press back or left to get to the settings menu.

There's one last setting for those with the SAFC-II, the knock sensor.

  1. Press left or back to the main menu and select "Monitor".
  2. On the next screen select 1 channel, press down until "Rev" is selected, and then next.
  3. It should display a nice engine revolution display. Start the car and let it idle.
    • The display should match your tachometer exactly. Rev it slightly to make sure.
    • If it doesn't you need to change your cylinder setting, see the troubleshooting section at the end.
    • Do not try to setup the knock sensor until the revolutions match or the knock sensor will not be setup correctly.
  4. Once you have verified it is correct press back to the main menu.
  5. Select settings.
  6. Select "Knk Set"
  7. Press right or next.
    • The car needs to be running, which it should be because you just verified the revolutions, right? Good.
  8. Move the cursor to the "1: 0" line. Next to it you will see it says "1500". Press the gas and try to hold the tachometer to a value between 1300 and 1700 RPMs.
  9. You should see your revs as the top number.
  10. Once you have it steady press right or next once.
  11. It will put a number in place of the 0 so it will read something like "1: 26".
  12. Now move down to the "2: 0" line and do the same with the tach between 3200 and 3700.
  13. It will enter a number in again like "2: 38".
  14. You've now calibrated the SAFC-II with your knock sensor. Press the left or back button once.


Your SAFC-I or II is now setup for your car. If you go into the monitor you should be able to display the current revolutions and throttle position and if you rev the engine both should display correctly. Now its time to tune! This procedure "should" only be done on a dyno, although people do street tune their cars. I will say that I don't recommend this but if you do decide to try it make sure you can tune in third gear somewhere and have a buddy in the passenger seat tuning, or you tune while he/she drives.

Whatever way you decide to do it a wide band O2 sensor is a must.

You will be adjusting the amount of fuel your engine receives at different RPM points and you can easily cause a lean condition resulting in detonation and a dead engine.

  1. You will make these changes from the Settings menu.
  2. Then selecting either "Hi-Thrtl" to adjust the curve when under hi throttle or "Lo-Thrtl" to adjust the curve under low throttle.
    • These hi and lo points are what you set them at a couple steps ago.
    • Left and right should cycle you through your rev points.
    • Up and down should adjust the fuel.

I can't tell you how to tune your car as every car is different but I can give some suggestions I have collected from myself and others:

  1. Lo throttle, at least the first couple points, can be tuned in park/neural. This is very helpful to even out a rough idle caused by performance cams.
  2. Aim for an A/F ratio of 13.1 for the most power throughout your RPM range.
  3. Always aim richer instead of leaner when adjusting the hi-throttle curve as that's your fuel under load.
  4. Hold the RPM you intend to tune and adjust it until you reach your desired A/F ratio and it stays steady. This will be your low throttle so use this as a guide for you're hi throttle. See step 3.
  5. If using a SAFC-II you can save two full sets of correction profiles under Settings -> Datafile. This is helpful to set a max power N/A profile then a slightly richer profile for nitrous so you can reduce the risks of detonation. Check your manual for more information.


Problem: SES Light comes on
Solution: There are many reasons for this but two common ones I found.
  1. You may throw a code when tuning because the PCM is looking for values from sensors that it's not getting.
    • For the most part you can ignore the SES light while tuning and reset it when done.
    • Disconnect the batter for 20-30 seconds to clear the code once the trouble is resolved.
  2. Once the SAFC is wired in the MAP sensor relies on the SAFC harness being connected.
    • Disconnect the harness and start up the car and you will get a MAP sensor failure.
    • Disconnect the batter for 20-30 seconds to clear the code once the trouble is resolved.
Problem: Revolutions are displaying wrong.
Solution: Change your cylinder setting.
  1. It should be an even number, every Saturn I have heard of either uses 2, 4, or 12. Try these settings and check the display.
    • This is a setting that can be changed while the car is running as long as you haven't made any corrections, which you shouldn't have until verifying this was right.
Problem: In the monitor for the MAP sensor you are reading boost and not vacuum.
Solution: Correct the sensor type, the sensor type is not right for your car.
  • The only exception I have found so far is having a SAFC-II on an OBDI car (91 - 95).
  • In this case if you find that you read boost when viewing the MAP sensor status try using 07/07 instead of 04/04.
  • Make sure you change this setting with the engine off.
  • Changing the sensor type when running can cause your PCM to see a sudden change in pressure causing a sudden rich or lean condition, either not being good for your engine.