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Message: [QUOTE="Racer X, post: 266236, member: 1934"] 4X4 4R100's and 4X2 4R100's with PTO option have 2 shaft sensors. In the case at the front is the turbine shaft sensor (TSS) with the OSS in the extension housing. The PTO models use a different TSS than 4X4 models do. Both sensors were added to the 4R100's to supplement the axle sensor so DTC's would be more accurate. Some DTC's had their meanings revised once the new sensors were added. Previously, the PCM had no sensor in the transmission itself to detect slip. When the axle sensor was out of range, the PCM assumed it was the transmission. It then would set a DTC for trannsmission slip. However, the problem could be in the axle itself or anything between axle and transmission, including drive-line components and transfer cases on 4X4's. Some 4x2 4r100's have the OSS on the side of the extension housing where the speedometer cable would enter the tail section. As mentioned, the actual DTC can be set due to a wiring problem or a bad or dirty sensor. Wiring is part of electronic control systems as it depends on it to work correctly. The system is advanced, but it can't tell the difference between mechanical failure and Electronic Control System failure. DTC's are a clue a tech uses to determine if a mechanical or electronic system failure exists. A bad PCM will set DTCs that are false. I mentioned bad PCM due to the Keep Alive Memory (KAM) DTC set. Yes, disconnecting battery power will set this code, which makes it common. Edge186 if your batteries went dead or you disconnected them, chances are thats what set the KAM DTC. A bad PCM thats lost it's memory circuits will too. Usually there are other symptoms when the PCM has lost it's memory capability. In the early days of electronic control systems they controlled the engine only. Precise control of air to fuel ratios in gasoline engines is where they really shine. They improved engine performance while actually exceeding emission and MPG standards imposed on the automakers by law. When it came to Power-train control, electronics were asked to take the place of the linkage, cable and vacuum signal that always worked reliably. Those are big shoes to fill. I remember when the magnetic fields from alternators and starters interfered with some early sensors which had to be revised. That was what coined the phrase "noisy signal." ;) Racer Product research and development consultant to the automotive industry. Certified specialist on automotive electronic control systems, diesel and gasoline engines, custom transmission, powertrain and engine builder. [/QUOTE]