Service Manual

3.10
ELECTRONIC FUEL INJECTION
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, intake 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 “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 initiating the “Blink Code”
sequence 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 (8000) 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 XP 850 RPM Limit:
Hard Limit - Fuel injector suppression occurs
• All Gears: 8000 RPM
Soft Limit - Spark timing suppression occurs
• All Gears: 7500 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 Sportsman XP 850 of the same model may be
used without system or engine component damage.
Maximum RPM Limit: 8000