Electronic Control Unit (Ecu); Operation Overview; Ecu Service; Ecu Replacement - Polaris 2008 sportsman 800efi Service Manual

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 (on/off), crankshaft position and speed
(RPM), throttle position, engine coolant temperature, air
temperature, intake manifold air 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 Malfunction Indicator
Light (MIL) (Check Engine Light) on 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 access the stored
fault code using a "blink code" diagnosis flashed out through the
Instrument cluster. 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, a rev-
limiting feature is programmed into the ECU. If the maximum
RPM limit (6500) is exceeded, the ECU suppresses the injection
signals, cutting off the fuel flow. This process repeats it self in
rapid succession, limiting operation to the preset maximum.
Sportsman 700 / 800 EFI RPM Limit:
Hard Limit - Injector suppression occurs
• High: 6500 (6600 - H.O engine - all gears)
• Low: 6500
• Neutral: 6500
• Reverse: 6500
• Park: 6500
Soft Limit - Timing suppression occurs
• High: None
• Low: 6300 (6400 - H.O engine - L/N/R/P)
• Neutral: 6300
• Reverse: 6300
• Park: 6300

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 re-initialized.
For the purpose of troubleshooting, a known-good ECU from
another Polaris ATV EFI of the same model may be used
without system or engine component damage.

ECU Replacement

1. Remove the retaining screws (2) holding the ECU.
2. With the Ignition turned off, disconnect the wire harness
from the ECU.
3. To install, reverse the procedures, reapply a small amount
of dielectric grease to the connector if desired. Tighten
screws to specification.
ECU Retaining Screws
10 in. lbs. (1.1 Nm)
FUEL INJECTION
= T
4.9
4