الموضوع: 2010 kia forte / soul input / output speed sensor set

. According to the AMG 98 shop manual the output speed sensor is a magnetic unit just like an electric guitar pickup. It consists of a permanent magnet surrounded by a wire coil. The sensor is mounted on the output of the transfer case opposite a gear-type rotor pressed onto the output carrier. The rotor and gear teeth interrupt the sensor magnetic field as they rotate. This induces an AC current in the sensor coil. The output sensor provides a voltage signal proportional to the vehicle speed. The sensor signals are used by the TCM (Transmission Control Module) / PCM (Power train Control Module) to control shift speed, pattern, torque converter clutch apply and the speedometer.
The TCM/PCM also monitors the Automatic Transmission Input (Shaft) Speed Sensor (A/T ISS) along with the Output Speed Sensor (OSS) during shifts in order to determine if a shift is occurring too fast or too slow. The TCM/PCM adjusts the signal to the transmission pressure control solenoid valve in order to maintain a set shift feel. The TCM/PCM also monitors the sensors after a shift to calculate the amount of slippage in that gear. It then adjusts the signal to the Transmission Pressure Control Solenoid in order to maintain slippage below a set amount. This is the way the 4L80-E transmission continuously adapts for normal wear in the transmission.

A failure of this sensor will affect shifting and converter clutch apply. Shifts will be erratic and the converter clutch applies at the wrong time. You can also experience and intermittent or loss of speedometer reading. It can cause the truck to go into backup / limp mode where it will only drive in 2nd gear. If you do get stuck out on the road with this problem sometimes shutting down the truck and then restarting it will allow the TCM/PCM to reacquire the correct signal from the sensor long enough to get home.
Because the primary part of the speed sensor is a strong magnet it has been attracting all the loose iron particles circulating in the transfercase since it was new (see picture of my sensor). These iron filings which range from the size of dust to slivers of ....l pile up on the sensor eventually causing the signal to degenerate. These false speed readings are fed to the computer which in turn causes all kinds of problems. John Ward tells me that this is not a problem on the input speed sensors because the transmission doesn't create the wear that the transfercase does. I also suspect that most of the junk floating around the transmission is picked up in the very fine transmission oil filter. John also said that "the transmission has a output speed sensor that is not used on the Hummer because we get the output speed from the T-case. This sensor is the same as the input speed sensor, which can be used as a spare in case the input speed sensor fails". John says "the failure of the input speed sensor is very unlikely".
Fortunately maintaining the Output speed sensor is very easy. The speed sensor is screwed into the top of the transfercase (see picture). You might want to remove the undercarriage protection plate (2 screws) under the transfercase first. All you have to do is remove the sensor which is a plug from the top and unscrew it from the case. Carefully clean off all the iron particles. If the sensor is chewed up in any way you will have to replace it.
The connectors and wires for the speed sensors are known to be troublesome at times. The connector is a standard GM part. Most failures are caused by water intrusion, due to a connector that is not well sealed.
AMG has come out with a 10 thousands shim washer (see picture) that goes under the sensor to space it out a bit from the rotor. Screw it back in and plug back the wire and you're all done. The shim is important. Owners that had light wear on the end of the sensor and were having intermittent problems with the truck going into limp home mode reported the problem solved when they installed the shim.
Trouble Shoot the Speedometer

The output speed sensor produces the signal that the cruise control and the speedometer uses. A quick way to test everything up to the speedometer is to try the cruise control. If the cruise control works and your speedometer doesn't then your speedometer is bad. If the cruise doesn't work then check the sender, DRAC and associated wiring .
While we're down there I would check the transfercase fluid which is Dextron III. Looking at the picture there are two rearward facing plugs in the case. These plugs use a hex wrench to open and may be on too tight. I usually have to take a piece of pipe over the hex wrench to get more leverage. Open the top plug and make sure the fluid level is 1/8" below the lower edge of the hole. Take a drop of fluid and put it on a white towel to check it's condition. According to the shop manual "normal fluid color ranges from dark red to light pink". In my experience fluid in good condition is a nice red color. Fluid that has been overheated will be dark red to brown in color. Burned fluid will be dark brown to black and smell burned. I can tell you from experience that if your truck has been driven 70 mph or faster, especially on a road trip you should check the transfercase oil ASAP.
You can drain the oil by removing the lower plug. Clean off the area around the drain and replace the plug. You can use a little liquid Teflon pipe sealer if you want. Stay away from Teflon tape because sometimes small pieces of it find there way into the case and can plug lubrication holes. Don't over-tighten the plug. If you find that your oil is burned or off color you might consider replacing it with one of the synthetic Dextron ATF's such as Amsol or Mobile. These products will take a higher temperature before they break down and it only takes 2 to 3 quarts to fill (buy 3 because you will spill some). The auto stores sell a "bottle pump" which screws into the oil bottle and allows you to pump the oil up into the fill hole. It's well worth the few bucks. I've filled my case with a funnel and gotten a Dextron bath at the same time.
The transmission has 2 speed sensors which are the same part that's used in the Hummer transfer case. I don't believe that the transmission output sensor is used on the Hummer. You may be able to swap the 2 sensors out using the one in the trans for the spare.


Notes:

I wrote a couple of weeks ago regarding my 98 TD going into limp mode and my speedo not working. I took the advice, got the shim for the output speed sensor and still had the problem. I located the DRA (thanks to Chuck and the very helpful picture in his article), took it apart, cleaned it out and that seems to have solved the transmission shifting problem. Everything appears to be working well except the speedo still doesn't work. However, the check engine light came on and after hooking it up to a scan tool, the following codes came up. P0501 VSS Signal out of range and P0722 Output speed sensor CKT no signal. Does anyone have any idea what these codes mean and what I should do now?
The vss (vehicles speed sensor) code is a problem with the sensor on the t-case not the transmission. Check the wiring to it. You should remove the sensor and check it with ohm meter to see if it has an open circuit. the other code for output speed sensor could have set when you removed it to install the shim or the shim set it out to far and it is not sensing the tone ring. The best way to diagnose this is to monitor the vehicle speed signal and output speed sensor signal under engine data on the scanner. If these sensors are not working correctly they will not show a signal on the data screen or it will be very erratic. if you don't have access to a scanner you will just have to try and replace both sensors.