Cub Cadet service manual M48 Tank, Figure

M48 Tank

•Do not connect a battery charger to the TANK with the key switch turned on.

•The ECU requires at least 7.0 volts to function.

•If the battery goes dead, or is disconnected, the adaptive memory in the ECU will be cleared. It will take 10-15 minutes of running, at normal operating temperatures, under a variety of loads and throttle settings to re-learn the full envelope of performance. Clearing the memory will also clear diagnostic trouble codes.

•The ECU receives signals from a variety of sen- sors. These include: crankshaft speed and posi- tion, throttle position, engine temperature, oxygen content of the exhaust gas, battery volt- age.

•There is an indicator light that flashes diagnostic codes in the event that there is a malfunction. If the signal from any of the sensors are not in the range that the ECU is expecting from compari- son to its adaptive memory, a code will flash.

•In the event of a malfunction, the ECU has a “limp home” mode that will allow it to plug in a fixed value in place of the reading from the mal- functioning sensor.

11.12.The Throttle Position Sensor tells the ECU what the position of the throttle plate is. It is essen- tially a potentiometer. See Figure 11.12.

Figure 11.12

•If a TPS fails, it will result in rough or erratic engine performance. If a “dead” spot develops in the potentiometer, the engine will run badly whenever the throttle is in a position that corre- sponds with the “dead” range of the TPS.

•The TPS can be checked with an Ohm meter, looking for “jumps” as the throttle is swept through its full range of travel.

•If the TPS mounting is disturbed for any reason, there is a Kohler-specified initialization proce- dure that must be performed.

11.13.The engine temperature has a bearing on the fuel/air mixture and ignition timing. The ECU “takes the engine’s temperature” with a ther- mometer in the engine oil.

•When the engine is cold, the oil temperature is the same as the ambient temperature. Being an air-cooled engine, as the engine warms-up, the oil temperature reflects a balance between engine load and ambient temperature when operating normally. This is sufficient for the pur- poses of the ECU.

•A bad temperature sender may result in rich fuel/ air mixture accompanied by an erratic idle and somewhat reduced WOT power.

•At 68deg. f, (20deg. c), the Ohm reading across the terminals of the oil temperature sensor should be in the 2375-2625 υ range.

11.14.In order to coordinate the timing of the fuel injec- tor triggering, as well as tune the fuel delivery and ignition timing to match the load applied to the engine, the ECU needs to know the speed that the crankshaft is spinning and the position of the crankshaft.

•There is a 60 tooth ferrite ring gear on the fly- wheel. This ring gear is separate from the starter motor ring gear. A Hall-effect pick-up mounted .049”-.069” from the ring gear gener- ates a pulse as each tooth passes by. The ECU counts the pulses to determine engine RPM.

•There are two consecutive teeth missing from the ring gear. The ECU gets a signal from each of the present teeth every 6 degrees of crank- shaft rotation. The 12 degree gap is positioned 84 degrees before cylinder #1 reaches TDC. This tells the ECU where the engine is in terms of piston position.

•Each time the engine is started, it will take 720 degrees of crankshaft rotation for the ECU to “find” the piston and begin working.

•Comparing engine speed to throttle position, the ECU can interpolate the engine load.

•If the cranks trigger signal fails to reach the ECU, the engine will not run.

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