4.16
ELECTRONIC FUEL INJECTION
9924096 - 2013 RANGER RZR XP 900 / RZR XP 4 900 Service Manual
© Copyright 2012 Polaris Sales Inc.
ELECTRONIC CONTROL UNIT (ECU)
Operation Overview
The ECU 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.
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.
For the purpose of troubleshooting, a known-good ECU
from another Polaris RANGER RZR XP 900 of the same
model 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. Carefully follow the ECU replacement instructions
provided in Digital Wrench® to ensure that all
essential data contained within the original ECU is
transferred to the replacement ECU.
2. Remove the black plastic cover by lifting up on the tab.
Remove the retaining screw that attaches the ECU to
the left rear fender well.
Maximum RPM Limit: 8750
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