4
4.9
9925723 R01 - 2015
RZR
900 Service Manual
© Copyright 2014 Polaris Industries Inc.
ELECTRONIC CONTROL UNIT (ECU)
Operation Overview
The ECU
1
is the brain or 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 power (on/off), intake air temperature, manifold
absolute pressure (load), engine coolant temperature,
crankshaft position and engine speed (RPM), throttle
position and battery voltage. The ECU compares the
input signals to the programmed maps in its memory and
determines
the
appropriate
fuel
and
ignition
requirements for the immediate operating conditions.
The ECU then sends output signals to set 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 on the instrument cluster 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.
RPM Limit: 8300
ECU Service
Never attempt to disassemble the ECU. It is sealed to
prevent damaged 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
preset. No internal servicing or readjustment may be
performed. If a problem is encountered and you
determine the ECU to be faulty, contact Polaris Technical
Service for specific handling instructions. Do not replace
the ECU under warranty without factory authorization.
For the purpose of troubleshooting, a known-good ECU
from another Polaris
RZR
900 of the same model and
year may be used without system or engine component
damage.
ECU Replacement
Although the need for ECU replacement is unlikely, a
specific replacement procedure is required to ensure that
all essential data contained within the original ECU is
transferred to the replacement ECU.
IMPORTANT: Refer to this procedure and carefully
follow all instructions provided in Digital Wrench.
1. Remove the driver’s seat and the ECU access panel.
2. Connect the Vehicle Interface Cable to the Digital
Wrench diagnostic connector. Go to the Special Tests
menu and select ECU Replacement. Carefully follow
the ECU replacement instructions.
3. Remove the four T-25 Torx screws
1
retaining the
ECU to the rear panel.
FUEL SYSTEM
