I think the speed sensor has failed on my 98 355 F1. Yesterday took the car to my shop to clean the motor. Did the usual yearly cleaning procedure, same as before. Only a 15 minute drive home and about half way the speedometer went dead and the F1 warning light came on. Made my home slowly and without issue except I could not up shift past second gear. Is there a possibility that that water has penetrated the speed sensor? Has never done this before. If so, is there a way to verify? I removed the sensor and took an ohm reading across the terminals. The first ohm reading was 550 ohms. I then reversed the polarity and the ohm reading was 1060 ohms. Has anyone checked the resistance before and if so are these readings normal? I would just like to confirm if the speed sensor has failed. I am thinking that water should not be an issue. I have driven in fairly heavy rain at times and never a problem before. Thanks
Park it in the garage with the decklid open (maybe even use a couple of fans to blow dry) for a few days to let it THOROUGHLY dry out, then see what happens Also, look for ANY connections in the engine bay which may have been loosened / dislodged by the engine washing. Simple deduction says that if it was working fine before the wash, something about the wash caused the problem --- it is doubtful that the sensor coincidentally failed, however it could have been damaged during that process somehow.
It is the sensor for the vehicle speed, left side of transmission, close to the left cv boot. Proper name is a pulse sensor, part number 14905.
Best way I know of is to use an oscilloscope and check the output of the sensor: it should give you a sine wave as the teeth pass by the sensor. And they can go bad when water gets in them (they are sealed but the sealant shrinks with time and thermal cycling)
If the 355 is the same as the 348 in this regard (I don't know this for a fact) the speedo sensor wires pass through the twist connector near the top of the left rear shock tower, and it MAY be possible that the connector isn't attached tightly (as suggested in finnerty's post). Seen it more than once. Easy to check.
That makes sense. Lets face it the car is 15 years old. A lot of heat cycles, maybe coincidental but still failed. Agreed about the method buT I do not have an oscilloscope, is there an alternative method to check?
Regarding the connector, the only connector I found was the sensor to harness connector. Don't know about 348 models.
No other good way to check w/o a scope. I would recommend swapping with the sensor from a buddy's car and see if the problem goes away ---- then, of course, you have indirectly confirmed that your sensor is bad. BTW, I believe the correct p/n is 149095 ---- assuming this is your part ---- Image Unavailable, Please Login
Yes, that is the part, got the wrong part number earlier. I am going to order the sensor. I have done a little more research and found that if the sensor fails on a F1 equipped car, the F1 warning light illuminates and the speedometer quits working and that is what mine does. There is chance that I may have a loose connection on the back of the speedometer itself and will check that too. I also found that occasionally the lift sensor fails, causing a fuse to blow, which is on the same circuit. Since I have no blown fuses, I am going to assume the speedometer sensor is the cause. When I install the new sensor I will update. Thanks for your help on this. Gary
You may want to keep the old one as a spare. After a few weeks, if it got some water leaked / forced into it, it may come back to life after it dries out . Ricambi has that sensor in stock for about $200, if you need a source. Hope that fixes it for you --- good luck .
You cannot check that sensor with an ohm-meter, it is not just a winding wrapped around a pick-up core. It has a circuit board inside with multiple components. They do fail quite often, and it is possible that water penetrated the sensor, or the shock of being hot and then hit with cold water caused it to fail. One wire is switched 12v power to the sensor, the other is output to the speedometer/F1 ECU and it grounds through the the outer shell. Brian Brown Patrick Ottis Co.
Thank you Brian, no wonder a simple ohm meter reading was of no help. I did order a replacement, hopefully I have it before the weekend. Gary
I received the new sensor and installed it last night. Road test and all is good. I guess there is no way to tell if it failed due to water migration or not. Coincidence that it failed after an engine wash? If that is the case, I am quite satisfied to replace the part. Obviously it was going to go any ways, glad it did not happen when taking a drive to go someplace fun. I also replaced two parts I thought should be replaced. First item is the cat temp sensor module for the bypass valve. I had replaced both left and right modules with the upgraded green ones. Thought it good time to replace the last one for the bypass valve. Second item is the crank sensor, the connector was looking a little rough. So, speed sensor was replaced, because it had to be done. Bypass temp sensor and crank sensor "while you're in there" Good little project, and big thanks to all for your responses. Gary
