Written by: Big Ross Pictures by: Big Ross PCM Info: Ford TIS DVD
Experience Level: Intermediate (Although written for beginners)
In this tutorial, I will explain how to install an Air/Fuel ratio gauge into your cougar. The pictures are taken during the install on my 1999 Cougar V6 ATX and I‘m installing a Sunpro gauge. I will also include install information for each year as I go along. Lets begin…
Disconnect negative connection to the battery. This is important, continuing without doing so could cause damage to your PCM (Powertrain Control Module). Most people will have top post connections, in the picture below, It shows the removal of a converted side post optima.
[My yellow top with the negative cable off]
Locate the power steering reservoir at the back left of the engine compartment as shown below. Remove the reservoir by lifting straight up. It is just clipped in and will slide right out. If you have trouble, try wiggling the reservoir back and forth and try to pull straight up again.
[The location of the power steering reservoir]
[Wiggling the reservoir to lift it out]
Once the reservoir is lifted out of it’s clips, push it off the side without too much force otherwise you could damage your power steering hoses. It should stay somewhat out of the way.
Grab a socket wrench and a long enough extension so you can easily remove the bolt on the PCM. The PCM is located behind where the power steering reservoir was located. I used a 10mm socket to unbolt the wire harness on the PCM shown in the picture below. Once unbolted, the harness should disconnect with ease.
To access all the wires connected to the harness, you need to remove the black plastic housing over the PCM harness. It wasn’t an easy task based on the room available, but it is the easiest to remove by prying the cover off with a small flathead screwdriver. Once off, you have the ability to search for the pin and locate the correct wire.
[Removing the black plastic housing off of the PCM harness]
Go inside your car and find the place you want to mount your gauge. I choose to mount mine inside the area where the stock gauges are. I also wanted to mount it in front of the check engine light since it was getting a bit annoying. I would much rather look at my air to fuel ratio then a bright orange light. I ran the wires behind the dash to keep them out of sight and make sure my car looks neat. Once you place and run the wires of your Air/Fuel ratio gauge, it is time to start hooking the wires up.
On my gauge, there are 3 wires. Here is the descriptions… Red Wire - 12v power wire to provide positive electricity to the gauge. It will be hooked up into the passenger fuse compartment. Black Wire - This is the ground wire for the gauge. It provides negative power to the gauge. It will be hooked up to a bare metal ground inside your car or can be ran to the battery. Green Wire - Can also be a different color such as violet. This is the o2 sensor sending wire. This wire will be spliced into the PCM. White Wire - Depending on the gauge you have purchased, there may be a white wire which is a dimmer for night use. It is connected to your headlight switch. I did not hook this up (yet anyways) so I did not add a tutorial about this wire.
First, we will run the green wire to the PCM. Drill a hole in your firewall to pass this wire through the interior into the engine compartment, The best place to run the wire through is the drivers side. If it is closer, it might be easier to run the wire through the passengers side. Since I have an ATX transmission, I have a spot on the drivers side where the clutch pedal would be placed and it is blocked by a rubber grommet. I just removed the grommet and passed the wire through the hole. Run the wire along the back of the engine compartment (zip ties may come in handy to keep the wire in places). Once the wire is ran the PCM, we can proceed to splice the wire.
[Open PCM harness]
If your gauge came with quick connects, it will be a lot easier to splice the wires. If not, you may want to run to your local auto parts store and pick up a package of quick connects.
Here comes the hard part. Depending on what year and engine your car has, you will have to find the wire to splice the green wire into. I will list the wires for certain cougars below. NOTE: Make sure you pay attention to which wire your splicing into since there could be more than one wire with the same colors. Always double check the wire before splicing into one.
[1999 Cougar V6]
+ Built before May 1999
- Pin number 87 (White wire with a red stripe)
+ Built after May 1999
- Pin number 35 (White wire with a blue stripe)
[1999 Cougar l4]
+ Built in 1999 (Includes Cougars built in/for early 2000 that may have the l4)
- Pin number 60 (White wire)
[2000-2002 Cougar V6]
+ Built from 2000 through 2002
- Pin number 87 (White wire with red stripe)
There should be a diagram on the harness which states the pin numbers. Find the pin number for your car and locate the wire. Double check to make sure it is the right wire. For my car, I had to splice into the wire going into pin 87 which was a white wire with a red stripe.
[It is hard to see but the wire that is being seperated from the harness is pin 87 which is a white wire with a red stripe]
Grad your quick connect and insert the green wire into the hole which doesn’t allow the wire to go all the way through. After, slide the wire coming from the PCM into the side of the quick connect that allows the wire to pass all the way through. Use pliers to squeeze down on the quick connect and latch the quick connect closed. The wire is now spliced into the PCM.
[I know, the wire running in is red instead of green but the green wire wasn't long enough, so I had to use some spare red wire I had to continue the run]
Now we have the run the ground and 12v power wire to the appropriate places. The ground should be attached to an area inside the cabin which is bare metal and clear of paint or grime. You can sand down a section to drill and mount the wire. I used the bracket that holds the dash up which is located on the right side of the drivers side behind the plastic cover. If you find it difficult to find a good ground, you can always run the ground wire through the firewall and connect it to your battery’s ground.
The last wire we need to run is the 12v power wire. Run the red wire to the passengers fuse panel located under the dash on the drivers side. You will need to find a fuse that controls something that only turns on when the ignition is on. One of the fuses that protects something that only turns on with the car is the radio. I used the radio fuse. Locate the fuse you want to use (look in the manual if you have trouble finding a fuse) and pull the fuse. You can get a fuse holder which allows you to splice a wire off a fuse (can be picked up at your local parts store) or you can do it the ghetto but very workable way without issues. Strip the red wire to show about an inch and a half of bare wire. Wrap the bare wire around one of the metal tabs of the fuse and put the fuse back in as light as you can get it. Now you can close the fuse panel.
If you have any wires dangling, try to keep then out of the way using zip ties.
Now that we have hooked up the gauge, we can start putting everything back together.
First, you will need to slide the black plastic cover back over the PCM wire harness. Once you do, you can go ahead and put the harness back onto the PCM. Bolt the harness back in. Do not bolt it very tight. Just enough to keep it in and sturdy. If you over tighten the bolt, it could snap or damage the harness/PCM.
[I couldn't fit the black housing back over the harness so I bolted it back in without it]
Slide the power steering reservoir back into place. Make sure you slide the clips back into their original slot otherwise it may not be held in properly.
Reattach the negative to the battery.
Start up your car! Check to see if the gauge is functioning properly. If you have followed all the steps, it should be giving a reading. It may bounce all over the place at idle. If your gauge doesn’t light or show a reading, you may have spliced into the wrong wire or your ground/12v power wire is not hooked up correctly. Hopefully it is working perfect for you.
If you have any other types of problems, using the troubleshooting section at the end of this tutorial.
Enjoy your new gauge and hopefully it will help you diagnose issues with your cougar in the future.
+ The gauge is not lighting up or not showing any information.
- Check all your connections to make sure they have good contact. If they are all good, you maybe have spliced into the wrong wire at the PCM. Make sure you have choose the right wire and try again. There is also a possibility that it is a bad gauge.
+ The gauge is bouncing around like a yoyo, is it a bad gauge or wrong wire?
- This is normal for some people. The gauge is fine and your wiring is correct. If you continue to get a yoyo effect while driving, double check your connection to the PCM.
+ The gauge shows information at idle but disappears when driving.
- You have spliced into the wrong wire at the PCM, find the right wire and try again.
If you have any questions contact me or post on this tutorial and we will gladly help you.
Thank you for reading my tutorial and I hope it will help you out while installing an Air/Fuel Ratio Gauge!
I wrote this tutorial for everyone who might have an issue installing an Air/Fuel gauge. I have a lot of trouble installing mine and I was very appreciative of everyone helping me on this install. Thanks everyone!