987.1 Always showing oil level full 5 bars

Hello, I have been troubleshooting Porsche 987.1 oil level sensing. No matter how much oil is in the engine, instrument cluster always shows five bars. Sensor has been replaced twice by the previous owner.I have also checked the resistance of the oil level sensor wires, short to power short the ground etc. I measured the voltage drop across the sensor and for sure the instrument cluster runs the test. I even increased the sensor resistance to simulate the low oil condition with same results. I purchased the cluster from eBay. However, I have the same issue with the used cluster. I’ve sent my original cluster to someone that can programmed it and it was programmed correctly to the vehicle build code. After cluster reprograming, same exact issue is there 5 bars every time. Reading the DME with icarsoft , I can read the oil temperature correctly. Instrument cluster 12V and ground is in spec and connector pinout is correct. Really getting puzzled on what is wrong and I wish I had PIWIS to read the cluster data. There are multiple treads that have similar issues but I never seen the exact problem that I am having. Thank you.

You have been incredibly thorough and methodical, that is a curious problem. Particularly since the icarsoft gives you the right reading. As much of a pain as it is, in the interim, you have to read it through the service port. If you are a member of PCA, this is exactly the kind of problem I would throw to one of their technical people who also have access to factory people.

Thank you sir. I have tried everything possible with the tools that I have. The icarsoft gives me the temperature only, not the level and the temp is measured by the DME and then broadcasted over CAN. The CAN bus is not jammed because everything else works flawlessly. Interesting part is that cluster runs the test, I can see the multimeter registering voltage drop across the sensor and it is always converting the value oil full level. I am not the PCA member, but I may have to join since this is really puzzling issue. 🙂

Where are you located? Maybe someone near you has a PIWIS ? That seems like the next step. This issue seems like a DME one. It’s like the gauge is giving an “adjusted” result. I’m not sure if this is possible with oil level. But it’s possible for coolant temp and mph. For example, the mph reading we get is adjusted up by about 2 mph. Perhaps an attempt to keep folks driving more conservatively. It’s like someone setting their watch to be 5 min fast so they won’t be late to stuff. just a wild idea on my part. I’m not sure if the oil level can even be adjusted like this. But since other things can, it might be an area to investigate.

I notice that your display isn't registering "full", it shows overfilled . That top segment should normally be off. Since each generation seems to measure oil level differently, I gave up trying to keep up on the subtle differences. For example, IIRC the 981 doesn't recalc the level until you do some kabuki dance in the trunk. On a 987.2 you need the engine at normal operating temp, but 987.1 is different. I wonder if there is another temp sensor that the DME isn't happy with. .

Thanks for the feedback. I reached out to the friend that knows the porsche tech. PIWIS is the next step for sure and I am opening PCA mebership to reach out to someone that knows exactly how the oil leveling is programmed. This is my interpertation of the 987.1 oil level sensing. Since my car is 987.1 the oil level is measured by the instrument cluster directly. The oil level sensor is a piece of wire that is submerged in the engine oil. The wire is very thin and resitance chages in respect to oil level. In other words the oil cools the wire and depending on the oil level it will cool it more or less. Once the cluster intitates the test, it records the voltage drop accross the sensor and then it converts it from analog to digital value. Micro controller inside of the clusetr has the look up table to know which digital value coressponds to the Level displayed. This is my understanding how the system works on the high level. The temperature is read by the DME and is reading correctly and it can be seen with the scanner. As you mentioned maybe the temperature has an impact to the calibration but I have tried all conditions including manipulating the resistance to force the voltage drop to the value tha t should read low oil. Thank you.

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This is a case where you need a diagnostic tool that can read the values that the DME is seeing from the oil-level sensor. The PIWIS should be able to do this. I have to try it - but I suspect most of the Foxwell Porsche tools can do it. ----------------------------------------------------------------------------------------- If the value as seen by the DME is changing with oil level changes (not easy to test since it involves taking a measurement, then removing or adding some oil, then taking another measurement) then the issue is what is the output being sent to the cluster look like. ----------------------------------------------------------------------------------------- One caveat here - if you are overfilled, and each time you measure the oil you're overfilled - and it displays overfilled (ie - top tiny segment lit up), then you won't see changes in the display. Adding a resistor in line with the sensor may not work since that increases the total resistance, which might mean it's just moved more in the direction of overfilled. ----------------------------------------------------------------------------------------- To really determine what's happening - you have to take a measurement when you absolutely KNOW the sump is underfilled.. that sounds scary, but I think being 1 liter low from the specified oil quantity (and make certain that quantity is spec'd for your engine, your year, your model) isn't going to hurt anything. 1 liter out of 7 or 8 liters isn't really that low, and if the engine is stationary is not going to expose the oil pump pickup to air. My first step would be - drain out 1 liter of oil - and do the measurement. If the measurement doesn't change - drain another liter out. Can you tell us the exact quantity of oil you're putting in when changing the oil? And the year/model/size of your engine? ----------------------------------------------------------------------------------------- This could be a chicken-little(1), or shoot the messenger(2) situation. First we have to determine that the engine is not overfilled. If not - then we have to resolve why the gauge thinks it is. (1) Chicken-little: The phrase "The sky is falling!" comes from the classic European folk tale of Chicken Little (or Henny Penny/Chicken Licken), a story about a chicken who panics and spreads a false alarm about the world ending after an acorn hits her head, leading other animals to join her hysterical quest to warn the king, only to be tricked and eaten by a fox. The idiom signifies a hysterical or mistaken belief that disaster is imminent. (2) Shoot the messenger: is a metaphoric phrase used to describe the act of blaming the bearer of bad news, despite the bearer or messenger having no direct responsibility for the bad news or its consequences. (Wikipedia)

BTW - want to get really confused: Google Search

Thank you for the feedback. This is 987.1 and it has the wire sensor, not the ultrasonic sensor like 987.2. The instrument cluster does the entire job to measure the level. DME only reads the temperature of the oil and broadcast the temp via CAN bus. I have been troubleshooting this for a while now and long story short, it really looks like the cluster is incorrectly coded or the internal analog to digital conversion is not correct. Hot wire sensor is resistive type, more oil means less resistance and less oil means higher resistance. 987.1 the oil check procedure is with engine off, preferably sitting for few hours or overnight. After trying so many things and 3 different oil level sensors, I drained the engine completely. I have tested all of the wiring and even perform the check with 5 different resistors directly at the instrument cluster. I also compared the sensor voltage drop in respect to oil level to someones table (found on this website) from the good known vehicle. This step eliminates the sensor wiring, and the sensor, at this point there is no doubt in my mind that something is wrong with the cluster or the coding. No matter what the resistance is or the actual oil level the cluster reads over filled. The cluster has been already programmed, and the programming is matched to my vehicle build and correct VIN. I really need to find someone that has PIWIS again, to check what is going on and if the coding is correct then I will need another cluster. 😐 Thanks so much for the comments and the help.

One thought comes to me.. from BMW motorcycle days.. BMW on one series of bikes added a marvelous new fully electronic fuel level sensor that required no float/resistor assembly. It used a flat printed strip of plastic, with two metallic grids printed on the plastic, held in a plastic assembly that reached from the top to the bottom of the tank. This seemed wonderful - initially - until they started failing. I had one of the bikes that had 7 sensor strips under warranty (each new strip came with a 2-year warranty.. meaning as long as they failed less than every 24-months, there was a perpetual warranty on the strips). I won't get into what the failure cause was (bad connection) or the resolution.. but... On that system, which used the two grids as a bridge circuit sort of temperature sensor, similar design, heat the strip, then measure the current draw to heat it, as the fuel cooled it, changing level resulted in changing current draw, converted into fuel level. When one of the strips failed, and had to be replaced, the instrument cluster had to be programmed for the value of the new strip . Each and every time. Just plugging in a new strip wouldn't work. The calibration involved removing all fuel from the tank, then using their diagnostics tool, tell the cluster the tank was empty, then fill the tank, and again using the diagnostics tool - tell the cluster the tank was full. I wonder if there is a procedure like that supposed to be done when an oil level sensor is replaced on a 987.1 ??

Good point, but to my knowledge so far I think no calibration is needed. Also no fault codes in the cluster or the DME. I am really determined to figure this out, college from work knows a local porsche tech and maybe he has the access to PIWIS. That is my next step. I will post back what I have found but it may take a while. Thank you, really value the feedback 🙂!