I have searched and couldn't find the answer to my problem, so I am asking for some help. My fuel gauge has worked off and on since the beginning of Covid since I started working from home. I have only put a little over 3,000 miles on the car in that time. This is where it gets confusing. Ever so often I would add a fuel additive (thinking I had something on the float) and a couple of the times, a few starts later, the gauge would actually start working. I have now given the car to my 16-year-old son and he apparently wants the gauge fixed. We have changed the fuel pump assembly on the driver's side and the sending unit on the passenger side and it is still not working. We also measured the resistance on both sending units and they appeared to be correct based on the information that we found. We also did the engineering test on the gauge cluster (premium) and the gauge went up and down like it was supposed to. We were able to get some codes from that test. They are B1A75:15 and then B1A76:15. After the conversion, the code appears to be a short to voltage on each side. We followed the pinpoint test in the workshop manual and we were unable to find any issues in the wiring. We are thinking that the gauge cluster is the problem at this time, but can't really find if there are any tests that can be done to the cluster prior to sending it off to be repaired.

Any help is greatly appreciated! Thank you!

 

I Could Not Find any TSB'S or SSM's For The Car Either By DTC's or Just Looking at Fuel Related Issues. Is Car Completely Stock No Module Type Modifications Upgrades Etc?? Anything Aftermarket Electrical Tied into System??

KC

 

Car is completely stock other than mufflers.

 

Give This a Look!

https://issautomotive.com/blogs/news...rument-cluster

KC

 

Thanks for the response! It sounds like that is the same as going in to "engineering mode"? We think we may have got an additional code this time after installing the gauge cluster and doing the "engineering mode" again. This code was P1243:06 and in addition to codes that we had before and still have which are B1A75:15 and then B1A76:15.- My understanding is that the P1243:06 is the computer detecting that there is more fuel in the passenger side tank (which is supposed to drain first) than the driver side tank. We checked the resistance of the fuel pump on the driver side tank and found that it was 12 ohms, which I believe is in spec for full. I believe the B1A75 and 76 codes are from the computer in the IPC detecting a short to power in the circuits of both sending units. However, we have checked voltage and resistance on both sides and it appears to be functioning correctly minus the codes. According to what I have read, the computer sets the fuel level to E when these codes are detected.

Would it make sense that all of these issues are caused by the instrument panel cluster itself? It feels like that's the only part that we haven't confirmed is working. I just don't want to throw more money at something that won't fix it, like I did with the fuel pump and sending unit..

Any help is appreciated. Thank you.

 

Realize As You Check & Correct Things It takes Awhile for the System To Reset. So You Could Fix Something and The Results May Not Come Instantly. Saw That in the Shop Manual When I was Gleaning Some Help For You!

Meanwhile a Small Gas Can May Need to Be a Companion Until it gets Sorted!

Kc

 

Here is Something That Can Happen As Well. Not Sure of Internals on Mustang Tank But if it Has Baffles in it and They Come Loose It Might Jam Up Sender. It's Worth a Peek Inside! Scrape Marks on Underside of Tank Would Be a Red Flag But Not the End All!

Just a Thought!

KC

 

Thanks again for all the responses! I am thinking before I send the cluster off for repair, we will run down the tank some more and recheck the driver side resistance. If that is in spec, the only other thing I can think to do is pull the driver side fuel pump assembly again and make sure nothing is jammed up like you suggest. If there isn't any other ideas by the time we run that tank down, then I guess we will send the gauge cluster off for repair and hope that fixes it.