99/01 Cobra cluster in GT

[Mustang5L5]

Perhaps someone on here might be able to help me brainstorm through this. This is something i've wanted to do for a long time, but perhaps it's just not achievable in the manner I want.

My Goal is to retrofit a 99/01 Cobra cluster into my GT, and have it fully functional with the correct vehicle mileage and correct speedometer calibration. Now, there are two ways to do this but neither one solves both problems simultaneously. Each method only fixes one of the two issues I need to solve.

Method #1) Swap the circuit board. That takes care of the issue with PATS programming and the odometer, but it fails to correct the speedo discrepancy as the board is still a GT board outputting values based on the 150MPH speedometer. Your odometer should still be correct however, as it's taking the VSS input and interpreting it correctly, it's just not scaled to sweep the speedometer right to account for the different speedometer value spacing. The speedo will show you slightly faster than you are really going. (EDIT: I do plan to try this and confirm the speedometer is in fact not correct and sweeping like it's the 150MPH face)

Method #2) Programming. Before you had to go to Ford for this. Now you can use Forscan and do it yourself. You are just performing PATS programming which is a service function in Forscan. 15 mins and it's done. Now, i've seen folks do this with Mach 1 and Bullitt clusters successfully. I have yet to confirm it can be done with the Cobra cluster. Also, this does not correct the odometer. You are stuck with whatever mileage the cluster had before.

There are some wiring differences as well to pay attention to. Next post.

 

[Mustang5L5]

The main wiring difference i've seen between 99-00 clusters and 01-04 clusters is Ford put the defrost circuit into the 01-04 clusters. When you hit the button, it sends a signal to the cluster which then outputs on a different wire to activate the relay. This is not present on the 99-00 clusters. SO, if you mix the generations up, it may cause an issue with popping fuses or having the defroster be on 24/7 even with car off.

I think this issue is a concern for 01-04 owners installing a 99 cluster. I beleive the pins on the board are a ground which shorts it out and causes the relay to be active. 99-00 owners can likely use 01 (or maybe even 03/04 cobra clusters) without issue.

But i think a good rule of thumb to use is for 99-00 GT owners to seek out a 1999 cobra cluster, and for 01-04 owners to use an '01 Cobra cluster. This ensure the defrost wiring is fully compatible with the cluster.

How can you tell the difference between the '99 and '01 cobra cluster? Well the warning lights. Specifically the far right light. On 99/00 cars, it says LOW COOLANT. On the 01-04 cars, Ford changed it to CHECK GAS CAP. So this is what you will want to pay attention to to identify the year of the 99/01 cluster as they are not the same.

I actually don't know what triggers the "check gas cap" indicator light, so I assume this will not be functional in 99-00 cars. More reason to just get the correct cluster for your year span.


99-00 Cluster wiring

01-04 Cluster wiring: Pin 8 & 9 on right plug are the added defrost logic, and pin 17 on left is deleted for the low coolant

 

[Mustang5L5]

So that’s where I am right now. I’m going to try out the easiest thing and just swap my GT board over. This should get me up and running with least amount of risk in terms of "bricking" the car. I am curious to try and see how speedometer calibration is done in the cluster. I actually don't think the descrepancy will manifest itself until much higher speeds. It looks like 80MPH is at the 12 o'clock position in a GT cluster, and the Cobra has 85MPH there. So 5MPH discrepancy at 80 isn't bad. However i'm the type of person that needs it to be correct.

The odometer should be correct because like i said, it's not a tire calibration that needs to be done. VSS is still taking the signal and interpreting it the same. It's just how the cluster is outputting the visual representation on the cluster that may be the issue.

Also, this is an '01 cluster. It will bother me not having the proper low coolant light for my '00 GT so i'll likely flip this back on ebay and track down a '99 cluster.

That's where I am. I'll fiddle with this as I have time as its not a high priority project.

 

[02 281 GT]

Have you tested the cluster to see where the mileage currently sits? If lower, you could probably just go with option 2 and set up a bench test scenario that allows you to advance the mileage until it reaches that of your GT.

 

[Mustang5L5]

Decided to play around with this tonight and check the wiring out. Now, this won't really apply to method #1 if you swap the board. This is really a watchout in case you decide to perform the PATS programming (or PATS delete) and just swap the entire cluster over. I think the benefit here is the speedo will operate correctly, but the downside is no mileage match.

But regarding Method #2, there is some wiring difference that you need to pay attention to. Specifically the defrost wiring into the cluster. Not sure if Ford decided to relocate the timing circuit to the cluster, but when you press the defrost button on a 01-04, a signal goes to the cluster and then another wire out to the relay. Assumption here is the timing circuit is in the cluster.

SO poking around, i found that this wiring is non-existent in the 99-00 harness. If you scroll up to post #2, the wire locations marked "NOT USED" do not have a wire present at all. Likewise, i managed to snag a couple connextors from a junkyard 01-04 car, and confirm that the 01-04 wiring diagram is accurate. What this means is the low-coolant wire is missing, but the two defrost wires are present. Long story short, the diagrams in post #2 are correct. Surprise surprise.

So, had to do a test. I plugged in the 01-04 cluster harness ends and tested continuity between the two defrost wires. (pin 9 and 10, small plug). I had zero continuity. That means what whatever happens inside the cluster is controlled and activated by something. My guess, power on allows the circuit to close when the defrost on wire is energized.

Next, i took the 01-04 cluster plugs and plugged it into my 99-00 cluster. I tested continuity and had it between pin 9 & 10. Now, i don't have a circuit diagram, but I would make a reasonale assumption that having these two wires always in continuity probably isn't going to cause a desirable outcome. I had read about folks having a constantly on defroster, and now see why.

SO, long story short. If you are going with method #2 and performing the PATS reprogram/delete, you will really want to pay attention to your clusters. 99-00 cars should use 99-00 clusters but they might be able to use a 01-04 cluster because they completely lack the wiring for the defrost. However they also lose the low coolant light for good. 01-04 cars should only use an 01-04 cluster because the 99-00 clusters will short the defrost wires and possibly cause a drain issue or even blown fuses. You can remove this wires and make the defrost inop if you want. Might be other solutions but that's beyond the scope of what I'm doing here.


CLiffs Notes for Method 2 (Pats reprogram/delete)
99-00 cars should seek a 99-04 cluster, possible can use 01-04 cluster but no low coolant light
01-04 cars should only use 01-04 clusters.


Now, one other minor difference between the two CObra clusters as well. 99 cobra cluster will have blue illumination, ANd 01 cobra cluster will be green. Here's '01. I have a 99 cluster on the way as I prefer blue.

 

[Mustang5L5]

Going to try Method #1 shortly. This is your basic circuit board swap that will carry over the PATS programming and your mileage. Downside, speedo off slightly. It's not something that can be recalibrated by a handheld tuner as its how the cluster interprets the data from VSS and outputs to the needle. The odometer should be 100% correct, but your needle is off.

Best way I can show it is like this.

Essentially when you are really traveling 80MPH on the GT cluster, it will show as 85MPH on the cobra cluster due to the spacing. Your odometer is correct, but you are off 5MPH at 80 (and 10mph off at 150). At normal speed like 40MPH, you are probably 3MPH faster than the needle is showing. Not really a huge deal i guess as long as you know this. Most importantly however, your odometer will still be correct. AGain, the cluster doesn't know what face is on it, so that's why the speedo will be off.

My GT has 70K miles on it, so keeping that true is important to me. SO method #1 will likely be the way I go. But i really want to try #2 first and see if i can find a way to correct the odometer.

 

[Mustang5L5]

Have you tested the cluster to see where the mileage currently sits? If lower, you could probably just go with option 2 and set up a bench test scenario that allows you to advance the mileage until it reaches that of your GT.

Looks like that won’t work.

 

[Mustang5L5]

Method 1 works as expected.

Everything works, and my mileage transferred over. Only real issue is my low coolant light (which works) now says check gas cap.

But I’m not thrilled with the 01-04 green lighting and it doesn’t match the blue in my ‘00. I have a ‘99 cluster in the mail which I assume is blue backlighting.

Didn’t test the speedo, but talked with someone on FB who confirmed my suspicion. The odometer is correct in how it measures miles, but the speedo is off. He said it was 6-7mph off at 80mph.

I’ll take it for a spin shortly but unless I report back otherwise (and edit this post) the speedo issue is true.

I’m probably going to try method 2 with the ‘99 cluster when it arrives.

 

[Mustang5L5]

SO tried Method #2.

This is essentially PATS programming, which can be done via ForScan. I've done it successful in the past as my car initially came with 1 key and I needed a 2nd. SO i know it works and its easy to do.

I plugged the '01 Cobra cluster in and fired up ForScan.

And it did NOT work. I repeated this 3 times (12 mins each time for PATS programming) and it would either display a solid THEFT or flash it quickly. EIther way, the car would not start. FOrScan will show module DTC"s and it showed a number of PATS errors specific to communicating with the PCM,

I have a suspicion this doesn't mean it can't be done, but I believe the issue is programming an 01+ cluster into a 99-00 car. I pulled the backplates off both and compared the boards and there are differences in the surface mount components in terms of what is present. I wouldn't be surprised if there is some software differences. Needless to say, I dont think Method #2 works here with the '01 cluster in an 99-00 car.

SO the '01 cluster will go back on ebay. '99 Cluster on the way. Stay tuned.

 

[Mustang5L5]

Got my 1999 Cluster. Main difference with this cluster is blue coloration vs green in the 01-04 clusters and the addition of the low coolant light.

Attempted method #2 again and failed on the first try, however I noticed with Forscan I could perform a "Module Initialization". SO I loaded up the PATS service function and picked this option. It went through it's procedure and asked me what part I replaced. I selected IC (instrument cluster) and it completed the initialization.

I then performed the PATS procedure and erased all previous key and registed my 3 keys with the cluster. This went off without a hitch.

As you can see, it worked! My car has 70K miles and I was pleasantly surprised to see this cluster has 65K. I also swapped LED's into the cluster first.

Unfortunately it started to rain, so no drive to verify the speedometer is accurate. My guess is that it will be. Tach and all other functions seem to work ok. DOwnside is the mileage. It's going to be off obviously.

I want to take it for a drive and confirm MPH is spot on, and then i'll go back to my original cluster. Ultimately I think I will go back to Method 1 with this cluster as keeping the miles accurate is VERY important to me as I don't want to cause a mileage issue on a 70K mile car that I intend to sell.

Unfortunately I need to pick between the mileage being wrong, or the speedometer displaying 4-8MPH off. I think I can handle the latter.

Unless someone has a method to adjust the mileage. I do not have the proper bidirectional OBD scanner to do this.

 

[Mustang5L5]

BTW my original GT cluster still works. I swapped it back in and it fired up using all my keys. Able to swap back and forth between both clusters so they are both currently programmed to my car/keys

 

[Mustang5L5]

Confirmed. Speedometer and odometer are spot on. Everything works as intended, just the mileage is off.

Ill probably go back to method 1 to keep my odometer record intact and just live with the speedometer being off by a factor of 1.06