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Composite
Vehicle
is equipped with either a MAP sensor or a MAF sensor.
RPM:
is a magnetic pickup but the scan tool just shows the RPM
LOAD:
the MAP sensor puts out an analog voltage. Idle at 18"Hg
will give us 1.0 v, and wide open throttle with 0"Hg will put
out 4.5 v. The MAF sensor option is also an analog voltage.
Idle will be about 0.5 v and wide open throttle will be about
4.5 v
TPS:
is an analog potentiometer that gives us a variable
voltage, with 1.0 v at closed throttle idle, and 4.5 v at wide
open throttle.
ECT:
Engine coolant temperature sensor that is a negative coefficient
thermister which gives 3.5 v at 32 degrees F and 0.5 v at 195
degrees F.
O2:
Normal zirconium oxygen sensor where values below 0.45 v are leaner
than 14.7:1 and values higher than 0.45 v are air-fuel ratios
richer than 14.7:1.
LFTRIM:
Given in %, where +% is adding time to the injector pulse width
to richen the mixture, and -% is subtracting time from the injector
pulse width. Normal values can be between + 10% and - 10%. Maximum
range is -25% to +25%.
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Scan Tool Diagnosis #2
The
questions below have be reprinted with permission from Professor Steve
McAfee, www.Smogsite.com
Composite Vehicle Specifications
are located on left side, under menu
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