Electronic Control Unit (Ecu); Ecu Overview; Ecu Rpm Limits; Ecu Service - Polaris ACE 900 2017 Service Manual

ELECTRONIC CONTROL UNIT (ECU)

ECU OVERVIEW

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The ECU is the central processing computer of the
entire EFI fuel/ignition management system. During
operation, sensors continuously gather data which is
relayed through the wiring harness to input circuits within
the ECU. Signals to the ECU include: ignition (on/off),
crankshaft position and speed (RPM), throttle position,
engine coolant temperature, intake air temperature,
intake manifold absolute pressure and battery voltage.
The ECU compares the input signals to the programmed
maps in its memory and determines the appropriate fuel
and spark requirements for the immediate operating
conditions. The ECU then sends output signals to set the
injector duration and ignition timing.
During operation, the ECU continually performs a
diagnostic check of itself, each of the sensors, and
system performance. If a fault is detected, the ECU turns
on the "Check Engine" light in the speedometer and
stores the fault code in its fault memory. Depending on
the significance or severity of the fault, normal operation
may continue, or "Fail-Safe" operation (slowed speed,
richer running) may be initiated. A technician can
determine the cause of the "Check Engine" light by
referencing the "Instrument Cluster Trouble Code
Display" and "Diagnostic Trouble Code Table" or by using
Digital Wrench®. The ECU requires a minimum of 7.0
volts to operate. The memory in the ECU is operational
the moment the battery cables are connected.
To prevent engine over-speed and possible failure, an
RPM limiting feature is programmed into the ECU. If the
maximum RPM limit is exceeded, the ECU suppresses
the injection signals, cutting off the fuel flow and retards
the ignition timing. This process repeats it self in rapid
succession, limiting operation to the preset maximum.
9929422 R02 - 2017-2019 ACE 900 Service Manual
© Copyright Polaris Industries Inc.

ECU RPM LIMITS

RPM Limit:
8300 RPM

ECU SERVICE

Never attempt to disassemble the ECU. It is sealed to
prevent damage to internal components. Warranty is void
if the case is opened or tampered with in any way.
All operating and control functions within the ECU are
pre-set. No internal servicing or readjustment may be
performed. If a problem is encountered, and you
determine the ECU to be faulty, contact the Polaris
Service Department for specific handling instructions. Do
not replace the ECU without factory authorization.
The relationship between the ECU and the throttle
position sensor (TPS) is very critical to proper system
operation. If the TPS is faulty, or the mounting position of
the TPS to the throttle body is altered, the TPS must be
adjusted.
For the purpose of troubleshooting, a known-good ECU
from another Polaris Vehicle of the same model number
and year may be used without system or engine
component damage.
FUEL SYSTEM
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