Chrysler PT Cruiser. Manual — part 739
opposite preset limit or switch point. The process
then repeats itself in the opposite direction.
Short term fuel correction will keep increasing or
decreasing
injector
pulse-width
based
upon
the
upstream O2 Sensor input. The maximum range of
authority for short term memory is 25% (+/-) of base
pulse-width. Short term is violated and is lost when
ignition is turned OFF.
Long Term
The second fuel correction program is the long
term adaptive memory. In order to maintain correct
emission throughout all operating ranges of the
engine, a cell structure based on engine rpm and load
(MAP) is used.
Ther number of cells varies upon the driving con-
ditions. Two cells are used only during idle, based
upon TPS and Park/Neutral switch inputs. There
may be two other cells used for deceleration, based
on TPS, engine rpm, and vehicle speed. The other
twelve cells represent a manifold pressure and an
rpm range. Six of the cells are high rpm and the
other six are low rpm. Each of these cells has a spe-
cific MAP voltage range Typical Adaptive Memory
Fuel Cells.
As the engine enters one of these cells the PCM
looks at the amount of short term correction being
used. Because the goal is to keep short term at 0 (O2
Sensor switching at 0.5 volt), long term will update
in the same direction as short term correction was
moving to bring the short term back to 0. Once short
term is back at 0, this long term correction factor is
stored in memory.
The values stored in long term adaptive memory
are used for all operating conditions, including open
loop and cold starting. However, the updating of the
long term memory occurs after the engine has
exceeded approximately 170°-190° F, with fuel control
in closed loop and two minutes of engine run time.
This is done to prevent any transitional temperature
or start-up compensations from corrupting long term
fuel correction.
Long term adaptive memory can change the pulse-
width by as much as 25%, which means it can correct
for all of short term. It is possible to have a problem
that would drive long term to 25% and short term to
another 25% for a total change of 50% away from
base pulse-width calculation.
TYPICAL ADAPTIVE MEMORY FUEL CELLS
Open
Throttle
Open
Throttle
Open
Throttle
Open
Throttle
Open
Throttle
Open
Throttle
Idle
Decel
Vacuum
20
17
13
9
5
0
Above 1,984
rpm
1
3
5
7
9
11
13 Drive
15
Below 1,984
rpm
0
2
4
6
8
10
12
Neutral
14
MAP volt =
0
1.4
2.0
2.6
3.3
3.9
Fuel Correction Diagnostics
There are two fuel correction diagnostic routines:
• Fuel System Rich
• Fuel System Lean
A DTC is set and the MIL is illuminated if the
PCM detects either of these conditions. This is deter-
mined based on total fuel correction, short term
times long term.
PROGRAMMABLE COMMUNICATIONS
INTERFACE (PCI) BUS
DESCRIPTION
The Programmable Communication Interface Mul-
tiplex system (PCI Bus) consist of a single wire. The
Body Control Module (BCM) acts as a splice to con-
nect each module and the Data Link Connector
(DLC) together. Each module is wired in parallel to
the data bus through its PCI chip set and uses its
ground as the bus reference. The wiring is a mini-
mum 20 gage wire.
OPERATION
Various modules exchange information through a
communications port called the PCI Bus. The Power-
train Control Module (PCM) transmits the Malfunc-
tion Indicator Lamp (Check Engine) On/Off signal
and engine RPM on the PCI Bus. The PCM receives
the Air Conditioning select input, transaxle gear
position inputs over the PCI Bus. The PCM also
receives the air conditioning evaporator temperature
signal from the PCI Bus.
The following components access or send informa-
tion on the PCI Bus.
14 - 24
FUEL INJECTION
PT
FUEL INJECTION (Continued)
• Instrument Panel
• Body Control Module
• Air Bag System Diagnostic Module
• Full ATC Display Head (if equipped)
• ABS Module
• Transmission Control Module
• Powertrain Control Module
• Travel Module
• SKIM
SYSTEM DIAGNOSIS
OPERATION
The PCM can test many of its own input and out-
put circuits. If the PCM senses a fault in a major
system, the PCM stores a Diagnostic Trouble Code
(DTC) in memory.
For DTC information see On-Board Diagnostics
(Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/POWERTRAIN CONTROL MOD-
ULE - DESCRIPTION) .
SPECIFICATIONS
TORQUE
DESCRIPTION
N·m
Ft. Lbs.
In. Lbs.
Air Cleaner Lid Screws
3.9
35
Crankshaft Position Sensor Mounting Bolts
8
70
Engine Coolant Temperature Sensor
18
13.2
165
IAC Motor-To-Throttle Body Bolts
4.5
40
MAP Sensor
4.5
40
Oxygen Sensor
28
20
Powertrain Control Module (PCM) Mounting
Screws
4
35
Throttle Body Mounting Bolts
11.75 ±4
105 ±20
Throttle Body Cable Bracket Bolts
11.75 ±4
105 ±20
Throttle Position Sensor Mounting Screws
6.2
55
Vehicle Speed Sensor Mounting Bolt
2.2
19.4
SPECIAL TOOLS
FUEL
Pressure Gauge Assembly C–4799–B
Fuel Pressure Test Adapter 6539
PT
FUEL INJECTION
14 - 25
FUEL INJECTION (Continued)
ACCELERATOR PEDAL
REMOVAL
(1) Remove the throttle cable from the throttle
body cam as described in Throttle Cable of this sec-
tion.
(2) Reach behind the top of the pedal shaft and
push the retainer toward rear of vehicle (Fig. 1). It
may be necessary to squeeze retainer ears together
on dash side of pedal shaft.
(3) Lift cable up through slot in top of pedal shaft.
(4) Remove nuts from accelerator pedal assembly
studs. Remove assembly from vehicle.
INSTALLATION
(1) Position accelerator pedal assembly on dash
panel. Install retaining nuts. Tighten retaining nuts
to 12 N·m (105 in. lbs.) torque.
(2) Place cable through slot in top of pedal shaft.
(3) While holding pedal lever, Push retainer clip
forward in vehicle engaging it into the pedal lever.
(4) Hold the throttle body lever in the wide open
position and install the throttle cable.
Spanner Wrench 6856
Fuel Line Adapter 1/4
O2S (Oxygen Sensor) Remover/Installer—C-4907
O2S (Oxygen Sensor) Remover/Installer - 8439
Fig. 1 Accelerator Pedal and Throttle Cable
14 - 26
FUEL INJECTION
PT
FUEL INJECTION (Continued)
ACCELERATOR PEDAL
POSITION SENSOR - 1.6L
DESCRIPTION
The Accelerator Pedal Position Sensor (APPS) is a
variable resistor that provides the PCM with an
input signal (voltage) (Fig. 2). The signal represents
throttle blade position. As the position of the acceler-
ator pedal changes, the resistance of the APPS
changes (Fig. 3).
REMOVAL - LHD
(1) Remove the air cleaner cover.
(2) Disconnect the negative battery cable.
(3) Unlock the electrical connector and then dis-
connect the electrical connector from the module (Fig.
4).
(4) Remove the mounting bolt.
(5) Remove assembly from the mountng bracket.
(6) Open the APPS module cover and disconnect
the cable from the cam and module.
INSTALLATION - LHD
(1) Open APPS module and connect the cable (Fig.
4).
(2) Install APPS module.
(3) Tighten the mounting bolt.
(4) Connect the negative battery cable.
(5) Install the air cleaner cover.
CRANKSHAFT POSITION
SENSOR
DESCRIPTION
The crankshaft position sensor mounts to the
engine block near the starter (Fig. 5).
The PCM uses the Crankshaft Position sensor to
calculate the following:
• Engine RPM
• TDC number 1 and 4
• Ignition coil synchronization
• Injector synchronization
• Camshaft-to-crankshaft misalignment (Timing
belt skipped 1 tooth or more diagnostic trouble code).
OPERATION
The PCM sends approximately 5 volts to the Hall-
effect sensor. This voltage is required to operate the
Hall-effect chip and the electronics inside the sensor.
Fig. 2 APPS MODULE
Fig. 3 ASSP MODULE OPEN
Fig. 4 PEDAL POSITION SENSOR
PT
FUEL INJECTION
14 - 27
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