
Electronic Engine Controls
WARNING
To avoid personal injury and/or vehicle damage, refer to the service precautions at the
beginning of this section.
General Information
The Engine Management System (EMS) uses several different sensors and actuators to
gather and control various emissions and driveability aspects of the vehicle. These may
include but are not limited to:
MAP
– Manifold Absolute Pressure Sensor
FTP
– Fuel Tank Pressure Sensor
ECT
– Engine Coolant Temperature Sensor
A/F
– Air Fuel Ratio Sensor
APP
– Accelerator Pedal Position Sensor
CKP
– Crankshaft Position Sensor
CMP
– Camshaft Position Sensor
HO
2
S
– Heated Oxygen Sensor
IAT
– Intake Air Temperature Sensor
KS
– Knock Sensor
MAF
– Mass Air Flow Sensor
TP
– Throttle Position Sensor
VSS
– Vehicle Speed Sensor
These sensors provide critical information to the EMS such as, barometric pressure,
atmospheric pressure, intake manifold/engine vacuum, fuel tank pressures and changes
as the vehicle is operated.
MAP Sensor
The EMS uses the MAP sensor on systems that have a Mass Airflow Sensor (MAF) as a
backup. The EMS also uses the MAP sensor as an EGR diagnostic device and as an
engine load verification device. The EMS system uses this information to calculate engine
load and EGR flow rates. The EMS uses speed-density calculations (non-mass airflow
sensor systems) to determine the required amount of fuel delivery.
FTP Sensor
The Fuel Tank Pressure (FTP) sensor is part of the evaporative emissions system. The
engine control system monitors gasoline vapor pressures in the fuel tank to determine fuel
tank sealing. The FTP sensor can be used in conjunction with an EVAP vent valve and an
EVAP canister purge valve.
Canister Purge Valve Only Vehicles
When ambient temperatures are above 68° Fahrenheit the gasoline in the fuel tank
vaporizes increasing fuel tank pressure. The FTP sensor is used to determine how much
Summary of Contents for TrailBlazer
Page 1: ......
Page 26: ...Fig 3 Typical body and undervehicle maintenance locations Refer to chart for descriptions ...
Page 29: ......
Page 30: ......
Page 31: ......
Page 175: ...Spring free length check Valve spring squareness check ...
Page 192: ...Front of piston mark ...
Page 361: ...5 3L Engine Except Saab Underhood Fuse Block 2003 2005 Early Production ...
Page 469: ...Removing the outer band from the CV boot Removing the inner band from the CV boot ...
Page 470: ...Removing the CV boot from the joint housing Clean the CV joint housing prior to removing boot ...
Page 471: ...Removing the CV joint housing assembly Removing the CV joint ...
Page 472: ...Inspecting the CV joint housing Removing the CV joint outer snap ring ...
Page 473: ...Checking the CV joint snap ring for wear CV joint snap ring typical ...
Page 474: ...Removing the CV joint assembly Removing the CV joint inner snap ring ...
Page 475: ...Installing the CV joint assembly typical ...
Page 553: ...9 Torque the lug nuts to specification 10 Lower the vehicle ...
Page 556: ...Toe in Frame Misalignment Frame misalignment ...
Page 588: ...Bleeding caliper ...
Page 624: ...Manifold gauge set components Refrigerant recovery recycling station ...
Page 676: ...A C Specifications ...
Page 677: ......