Cub Cadet Challenger 550, Service Manual

Page: 252 / 255

Electrical component replacement
Most UV dealerships and parts suppliers will not accept the return of any electrical part.
If you can’t determine the exact cause of any electrical system malfunction, then you
purchase a new electrical component(s), install it, and then find that the system still
does not work properly, you will probably be unable to return the unit for a refund.
Consider any test results carefully before replacing a component that tests only slightly
out of specification, especially resistance. A number of variables can affect test results
dramatically. These include: the testing meter’s internal circuitry, ambient temperature
and conditions under which the machine has been operated. All instructions and
specifications have been for accuracy: however. Successful test results depe nd to a
great degree upon individual accuracy.
ECU unit
This is the brain for the UV. The ECU controls all the electrical and motor systems on
the UV. It sends out voltage to the sensors which use the voltage to measure
something. In their processing of the measurement they use up some of the voltage
that was sent, the remainder of voltage is read by the ECU, this reading tells the ECU
exactly what measurement the sensor got and the ECU adjusts fuel delivery
accordingly. There are very few tests for the ECU. Test all the sensors and if everything
else tests properly, re flash the ECU. If this does not fix the problem replacement of the
ECU is necessary.
Re flash procedure.
Set the Parking Brake. Make sure the shift lever is in the neutral position. Start the UV.
With your foot on the Brake, push down the accelerator pedal slowly to the floor. The
motor will peak until the rpm’s reach the rev limiter. Keep your foot on the accelerator
pedal while turning off the ignition. Once the motor comes to a complete stop you can
release the accelerator pedal. Wait approximately 15 seconds and you should be able
to turn the ignition key to the on position and fault codes should be gone.
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