Fuel Gauge and clock Issues on Cayman 987.2

Hello Fellow Caymanians First time member and post. I'm sorry if there is a answer too my issue, but I haven't been able to find it anywhere. My car is a 2011 987.2 , 2.9PDK right hand drive, Australia My problem has been so annoying and frustrating, I am hoping someone has had similar problems and found a fix. Problem 1,When I start the car every time the clock starts at 12:00 and after 2-3 minutes it gives the correct time, I can live with that. Problem 2, This I can't live with. The fuel gauge randomly after switching off the car and back on even after 5 minutes goes from full to yellow light empty, and it will not read full again doesn't matter how many times I switch the car on and off, even tried disconnecting the battery. Everything I read said battery or fuel sender, I replaced the fuel sender, $600 later problem still there, battery is always on trickle charge and has been load tested, in perfect condition. Had the car at a Porsche dealer and they had it on the PIWI 3, no fault codes,( Dealer had no answer) he reset the cluster, problem still there. I have taken out the sender and plugged it back in and move it up and down out of the tank and the gauge works fine. Sometimes it will be fine for 3 or 4 days and then, I stop somewhere and restart it and it is showing empty, even though the tank has plenty of fuel in it. I've checked many times and the sender is not catching on anything in the tank. Since I do many track days in the car it is so frustrating, when I get to the track it is showing half full, I do 6 laps I come in and switch it off, next session go back out and now it is showing empty and I don't know where I am at, regarding fuel level. The only reason I mention the clock in the case it is somehow connected to the fuel gauge issue. Any ideas or suggestion would be appreciated. Thank You in Advance Loypee

Loypee, welcome to the forum! Your clock is functioning normally, although the time set should happen as soon as you put the key in the car. The clock will spin around through about 24 hours and back and finally settle on the actual time. The clock is set to 12 when the computers in the car turn off (about 15 minutes after the key is out and the door is closed) and the power to it is shut down (to save standing battery life.) When you power on the computers again, a signal with the time is sent via the CANBUS to the clock telling it what time it is and to set itself. The dancing hands is it setting itself. So take the clock out of the equation. The fuel sensor is typically resistive - a float that moves an arm that turns a potentiometer that varies in resistance depending on the position of the arm. It will have a minimum and maximum value. Minimum is likely 0 Ohms. If you don't own an ohmmeter and know how to use one - you need to find someone who does. Here is the diagram of the fuel sensor ("rest of world", ie - not US): A2 and A3 go directly to the instrument cluster. The other portion of the sensor is supposed to shut off the fuel pump if the tank is empty since the fuel pump is lubricated and cooled by the fuel flowing through it. You want to read the resistance between A2 and A3 when it's working normally and when it isn't. See if the sensor is still an issue (despite being replaced). It probably is best done with the tank full in order to have a standard fuel level that you're measuring against. let us know what you read. You may also be able to do some diagnostics with a tool such as a Durametric or Foxwell or Launch.. you need a diagnostics tool that can read the sensor value. Again - getting readings when it's working and not working will be important. Since the sensor goes directly to the instrument cluster - and you've replaced the sensor - my WAG is a wiring issue between the sensor and cluster, or - much more expensive - a bad gauge in the cluster. Since you said you've removed the sensor and moved it by hand and the gauge display was correct, I'm going to guess that act of removing it somehow cleared the wiring issue temporarily. I'd be looking REALLY carefully (eye-loupe or macro-camera on a phone) at the connector to the sensor and the wiring near it. Good luck, let us know how it works out. BTW - when you have a chance, go to our New Member Intro forum and tell us more about yourself and your Cayman! --> New Member Introductions

Hi Don You sound like a very knowledgeable person. Firstly the Durametric is off no use on the 987.2 Cayman, it can not recalibrate the sender or have live readings of fuel level, that comes from Durametric support. I hope I explain myself so that you can follow what I'm saying if not clear please ask. I'll attach as many phots as I can. I removed the sender from the tank and bench tested it, 100% working thru the range on the ohm meter, 10ohm full and 300ohm empty and everything in-between. Put it back into the tank which had 12 liters (about 3gal) of fuel and hooked up the ohm meter to the 2 middle connectors which is the float resistance wires with no battery connected but all plugs were connected. The reading was 136ohm (IMG 1670) then I added 20 liters of fuel (5gal), so I have a total of 32litre (8gal) and the reading was 95 ohm (IMG 1671), makes no sense. Then I disconnected the plug and put the ohm meter directly on the 2 float sender wires (nothing else was connected) and I got 140ohms, which is about right, the tank is just below half full. (IMG 1672).I measured the resistance in the plug with no battery connected and got 426ohms (IMG 1673). Now it gets really weird, I connected the battery and started the car and I got -1446 ohm (IMG 1674). The last image shows my gauge even though it has 8 gallons in it. There you have it Don, I keep reading other peoples comments and a common thing keeps coming up Battery batter battery, my car starts fine it's always on a trickle charge and it tested ok under load, the only thing it came up with on the battery was that the CCA was down to 206, where the battery specs are 760CCA. The battery tester in the shop said it starts fine the voltage is 12.4Volts, it should be fine. I don't know how old the battery is, I tried looking up the Varta code but my Russian is not too good. Sorry for the drawn out explanation, but hopefully you can make some sense out of it. Best Regards Danny

I'm not sure I have an actual answer to your question, but I think you may be making a mistake with some of your readings. The fact that you're getting a negative ohm reading means that you have voltage on the lines... this makes sense if you have the sender connected to the car, and the car is started/running, because the control module (whichever one it is) is sending voltage to the sender in order to generate a reading. In other words, you cannot measure resistance of the sender when it's powered and connected to the car... it won't give you correct readings. For that matter, due to resistances in the "reading" circuit in the module, you also cannot properly measure resistance of the sender when it's connected at all, even if it's not powered (unless, for some reason, the reading circuit in the module has a very high impedance/resistance). The reason is because you will then be reading the resistance of two parallel circuits - the sender circuit and the impedance/resistance of the module's reading circuit. Again, this will give you false and useless information. Based on your numbers from the disconnected testing, it sounds like your sender is providing correct readings when disconnected (even by your admission). That proves it's working properly. (Another suspicion I had was that maybe your tank was dented or something, causing unexpected levels for different capacities, but it sounds like that is ok as well, so far). Therefore, if the readings are still going wonky, then this means the wires to the module or the module itself are suspect. Since you noted some other issues with other parts of the car, I might start looking at the module itself, particularly if it's the same one as the other issues you are seeing. One thing you could do to confirm it's not a dashboard issue is to use PIWIS or some other CANbus reader to see what the actual readings are showing on the bus, to make sure they match up. Assuming you can actually do that, of course. If those are correct, then the sender-reading module is probably fine and then it could be an issue in the dash that's causing issue with the display of the value. I think this is far less likely, but just wanted to mention it. EDIT: As I look at your last photo, I see "PSM failure" reported on your dash. Are you seeing other such failure messages on the car? If so, then I'd REALLY suspect a module issue, or some other problem. You need to chase those down completely. The thing to remember here is that this car (like many modern cars) is not taking a straight voltage reading from the sensor and sending it to the dash... it's reading it on some module, converting it to a CAN signal, then sending it digitally to other modules which then do things and display on the dash. It's not an old-school voltage reading, even though it's a "needle" on the dash! So just measuring voltages and resistances won't troubleshoot the entire system... there's a LOT more to it than that. This is also why people talk about the battery FIRST on these cars, because if a module is unhappy, all sorts of hell breaks loose. What is the voltage on your battery or the car when the car is NOT running? Just being able to start doesn't mean it's fine, necessarily...

That's an excellent response of accurate info from @schwinn - couldn't say it better myself. An "in-circuit" reading is almost never going to be accurate, with the system powered up or not. I really wanted to see the numbers of the sensor ALONE when installed in the tank, just in case there was something really odd going on that was binding up the movement of the sensor arm. And your half-tank reading pretty much reveals there isn't. I'll try to spend some time later today with my Foxwell NT530 and see what diagnostics it offers for the fuel level circuitry on the 987.2. Hopefully it's better than the Durametric (it seems to be better in other respects for this model..)

Thank you Schwinn Don't worry about the PSM Failure that always comes up when you disconnect the battery and goes away after 2 miles of driving. Just for the hell of it I will go and buy a new battery today!!!!! Regards Danny

Be sure the battery is fully charged before using the car to charge it. People often think this is ok, but if the new battery is low, the alternator has to make up for the charge and this strains it... sometimes to failure. Ask me how I know (not on this car, but a previous one many years ago). Again, if you can measure the voltage, that helps... it would be good to know what the current battery has, and what the new one has. For example, here is a ROUGH guide for voltage vs charge level: BU-903: How to Measure State-of-charge Note that this shows 12.65 and higher = fully charged, and 0% is 11.89... that's not a wide range, as you can see... Again this is a ROUGH guide. The article mentions that this is not the ideal way to measure SoC, but it's easy so most people do this... but it's not "gospel"... you could have "ok" voltage and still have a bad battery. On a sensitive vehicle (like most modern ones) it's easier to just change the battery, particularly if it's more than a few years old. Incidentally, how old is your battery? It should say this somewhere on the casing...

SORRY guys I have taken so long to give you a result to my fuel gauge problem. It has taken me this long to use up a full tank of petrol (Gas). Well. where do I start, as I said above I am going to buy a new battery and I did that same day, straight after I went to a gas station and filled up. The first thing that happened, the fuel gauge went straight to full, not a slow climb and my clock was not showing 12:00 every time I switched off the car and it kept the AM and PM time settings, where as before it wouldn't. Today the tank was nearly empty and I filled up again for the second time and bingo straight to full with no problems. As I mentioned before on many forums people said Battery Battery Battery and I kept thinking it can't be the battery because my car starts fine every time. When I had the battery tested it showed low cranking amps of 206 and it should be around 760, I thought that's no good but even the battery guy said "If it starts don't worry about it" Months of frustration, $600 for new sender, Cluster in and out many times, fuel sender in and out (I Lost Count). Fingers crossed that the new battery fixed the problem of the Fuel gauge and clock....but so far so good I hope this helps anybody else experiencing similar issues... Best wishes Danny

We hope that solves the problem for you as well, and thanks for posting back! Yes, we emphasize battery because the car is so sensitive to it... we speak from experience, haha! Again, glad it's squared away now, we all hope!