1993 CHEVROLET PLYMOUTH ACCLAIM Service Manual

coolant level ESP inoperative relay android auto fuel consumption oil additives

Page 449 of 2438

CHEVROLET PLYMOUTH ACCLAIM 1993 Service Manual pick-up (a Hall Effect device and magnet) through
which the shutter blades rotate. As the shutter
blades pass through the pick-up, they interrupt the
magnetic field. The Hall effect device in the pic

pick-up (a Hall Effect device and magnet) through
which the shutter blades rotate. As the shutter
blades pass through the pick-up, they interrupt the
magnetic field. The Hall effect device in the pick-up
senses the change in the magnetic field and switches
on and off (which creates pulses), generating the in-
put signal to the PCM. The PCM calculates engine
speed through the number of pulses generated. On 2.5L MPI (flexible fuel AA-Body) engines, one
of the shutter blades has a window cut into it. The
PCM determines injector synchronization from the
window. Also, the PCM uses the input for detonation
control.
DISTRIBUTOR PICK-UPÐ3.0L ENGINE
The distributor pick-up provides two inputs to the
powertrain control module (PCM). From one input
the PCM determines RPM (engine speed). From the
other input it derives crankshaft position. The PCM
regulates injector synchronization and adjusts igni-
tion timing and engine speed based on these inputs. The distributor pick-up contains two signal gener-
ators. The pick-up unit consists of 2 light emitting
diodes (LED), 2 photo diodes, and a separate timing
disk. The timing disk contains two sets of slots. Each
set of slots rotates between a light emitting diode
and a photo diode (Fig. 17). The inner set contains 6
large slots, one for each cylinder. The outer set con-
tains several smaller slots. The outer set of slots on the rotating disk repre-
sents 2 degrees of crankshaft rotation. Up to 1200
engine RPM, the PCM uses the input from the outer
set of slots to increase ignition timing accuracy. The outer set of slots contains a 10 degree flat spot.
This area is not slotted (Fig. 17). The flat spot tells
the PCM that the next piston at TDC will be number
6. Each piston's position is referenced by one of the
six inner slots (Fig. 18). As each slot on the timing disk passes between the
diodes, they interrupt the beam from the light emit-
ting diode. This creates an alternating voltage in
each photo diode which is converted into on-off
pulses. The pulses are the input to the PCM. During cranking, the PCM cannot determine which
cylinder will be at TDC until the 10 degree flat spot
on the outer set of slots rotates through the optical
unit. Once the flat spot is detected, the PCM knows
piston number 6 will be the next piston at TDC. Since the disk rotates at half crankshaft speed, it
may take up to 2 engine revolutions during cranking
before the PCM determines the position of piston
number 6. For this reason the PCM energizes all six
injectors at the same time until it senses the position
of piston number 6.
COOLANT TEMPERATURE SENSOR
On 2.2L TBI, 2.5L TBI and 2.5L MPI engines, the
coolant temperature sensor is installed behind the
thermostat housing and ignition coil in the hot box
(Fig. 19). On 3.0L engines the sensor is located next
Fig. 16 DistributorÐ2.5L MPI (Flexible Fuel AA-Body)Fig. 17 Distributor Pick-upÐ3.0L Engine
Fig. 18 Inner and Outer Slots of Rotating DiskÐ3.0L Engine
Ä IGNITION SYSTEMS 8D - 7

Page 450 of 2438

CHEVROLET PLYMOUTH ACCLAIM 1993 Service Manual to the thermostat housing (Fig. 20). The sensor pro-
vides an input voltage to the powertrain control mod-
ule (PCM). The sensor is a variable resistance
(thermistor) with a range of -40ÉF to 265ÉF

to the thermostat housing (Fig. 20). The sensor pro-
vides an input voltage to the powertrain control mod-
ule (PCM). The sensor is a variable resistance
(thermistor) with a range of -40ÉF to 265ÉF. As cool-
ant temperature varies, the sensors resistance
changes, resulting in a different input voltage to the
PCM. The PCM contains different spark advance sched-
ules for cold and warm engine operation. The sched-
ules reduce engine emissions and improve
driveability. Because spark advance changes at dif-
ferent engine operating temperatures during warm-
up, all spark advance testing should be done with the
engine fully warmed. The PCM demands slightly richer air-fuel mixtures
and higher idle speeds until the engine reaches nor-
mal operating temperature. The coolant sensor input is also used for radiator
fan control.
MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR
The MAP sensor reacts to absolute pressure in the
intake manifold and provides an input voltage to the
powertrain control module (PCM). As engine load
changes, manifold pressure varies. The changes in
engine load causes the MAP sensors output voltage
to change. The change in MAP sensor output voltage
results in a different input voltage to the PCM. The input voltage level supplies the PCM with in-
formation relating to ambient barometric pressure
during engine start-up (cranking) and engine load
while its operating. The PCM uses this input along
with inputs from other sensors to adjust air-fuel mix-
ture. On 2.2L TBI, 2.5L TBI and 2.5L MPI (flexible fuel
AA-body) engines, the MAP sensor is mounted to the
dash panel (Fig. 21 or Fig. 22). On 3.0L engines, the
sensor is mounted to a bracket across from the dis-
tributor (Fig. 23). The sensor is connected to the
throttle body or intake manifold with a vacuum hose
and to the PCM electrically.
AUTO SHUTDOWN (ASD) RELAY AND FUEL PUMP
RELAY
The powertrain control module (PCM) operates the
auto shutdown (ASD) relay and fuel pump relay
through one ground path. The PCM operates the re-
lays by switching the ground path on and off. Both
relays turn on and off at the same time. The ASD relay connects battery voltage to the fuel
injector and ignition coil. The fuel pump relay con-
nects battery voltage to the fuel pump and oxygen
sensor heating element. The PCM turns the ground path off when the igni-
tion switch is in the Off position. Both relays are off.
When the ignition switch is in the On or Crank po-
sition, the PCM monitors the distributor pick-up sig-
Fig. 19 Coolant Temperature SensorÐ2.2L TBI, 2.5L TBI and 2.5L MPI Engines
Fig. 20 Coolant Temperature SensorÐ3.0L Engines
Fig. 21 MAP SensorÐ2.2L and 2.5L TBI Engines
8D - 8 IGNITION SYSTEMS Ä

Page 451 of 2438

CHEVROLET PLYMOUTH ACCLAIM 1993 Service Manual nal. From the pick-up signal, the PCM determines
engine speed and ignition timing (coil dwell). If the
PCM does not receive a distributor signal when the
ignition switch is in the Run position, it w

Page 452 of 2438

CHEVROLET PLYMOUTH ACCLAIM 1993 Service Manual up. Refer to Auto Shutdown (ASD) Relay and Fuel
Pump Relay in this section.On 2.2L TBI, 2.5L TBI and 2.5L MPI engines, the
ignition coil is mounted to the thermostat housing
(Fig. 29). On 3.0L engine

Page 453 of 2438

CHEVROLET PLYMOUTH ACCLAIM 1993 Service Manual 2.2L TBI, 2.5L TBI, 2.5L MPI AND 3.0L IGNITION SYSTEMSÐDIAGNOSTIC PROCEDURES
INDEX
page page
Coolant Temperature Sensor Test ............ 13
Failure to Start TestÐ2.5L TBI and 3.0L Engines . 12

2.2L TBI, 2.5L TBI, 2.5L MPI AND 3.0L IGNITION SYSTEMSÐDIAGNOSTIC PROCEDURES
INDEX
page page
Coolant Temperature Sensor Test ............ 13
Failure to Start TestÐ2.5L TBI and 3.0L Engines . 12
General Information ....................... 11
Ignition Coil ............................. 11 Manifold Absolute Pressure (MAP) Sensor Test . 13
Poor Performance Test .................... 13
Spark Plugs ............................ 11
Testing for Spark at Coil ................... 11
GENERAL INFORMATION
For additional information, refer to On Board Di-
agnostics in the Fuel Injection General Diagnosis
sections of Group 14. Also, refer to the DRBII scan
tool and appropriate Powertrain Diagnostic Proce-
dures Manual.
SPARK PLUGS
Faulty or fouled spark plugs may perform well at
idle speed, but frequently fail at higher engine
speeds. Faulty plugs can be identified in a number of
ways: poor fuel economy, power loss, decrease in en-
gine speed, hard starting and, in general, poor en-
gine performance. Spark plugs also malfunction because of carbon
fouling, excessive electrode air gap, or a broken insu-
lator. Refer to the General Information Section of
this group for spark plug diagnosis.
IGNITION COIL
The ignition coil is designed to operate without an
external ballast resistor. Inspect the coil for arcing. Test the coil according
to coil tester manufacturer's instructions. Test coil
primary and secondary resistance. Replace any coil
that does not meet specifications. Refer to the Coil
Resistance chart. If the ignition coil is replaced due to a burned
tower, carbon tracking, arcing at the tower, or dam-
age to the terminal or boot on the coil end of the sec-
ondary cable, the cable must be replaced. Arcing at the tower will carbonize the nipple which, if it is con-
nected to a new coil, will cause the coil to fail. If a secondary cable shows any signs of damage,
the cable should be replaced with a new cable and
new terminal. Carbon tracking on the old cable can
cause arcing and the failure of a new coil.
TESTING FOR SPARK AT COIL
WARNING: APPLY PARKING BRAKE AND/OR
BLOCK THE WHEELS BEFORE PERFORMING ANY
TEST WITH THE ENGINE RUNNING.
CAUTION: Spark plug cables may be damaged if
this test is performed with more than 1/4 inch clear-
ance between the cable and engine ground.
Remove the coil secondary cable from the distribu-
tor cap. Hold the end of cable about 6 mm (1/4-inch)
away from a good engine ground (Fig. 1). Crank the
engine and inspect for spark at the coil secondary ca-
ble. There must be a constant spark at the coil second-
ary cable. If the spark is constant, have a helper con-
tinue to crank engine and, while slowly moving coil
secondary cable away from ground, look for arcing at
the coil tower. If arcing occurs at the tower, replace
the coil. If spark is not constant or there is no spark,
proceed to the failure to start test. If a constant spark is present and no arcing occurs
at the coil tower, the ignition system is producing
the necessary high secondary voltage. However,
COIL RESISTANCE
Ä IGNITION SYSTEMS 8D - 11

Page 454 of 2438

CHEVROLET PLYMOUTH ACCLAIM 1993 Service Manual make sure that the spark plugs are firing. Inspect the
distributor rotor, cap, spark plug cables, and spark
plugs. If they are in proper working order, the ignition
system is not the reason why the e

make sure that the spark plugs are firing. Inspect the
distributor rotor, cap, spark plug cables, and spark
plugs. If they are in proper working order, the ignition
system is not the reason why the engine will not start.
Inspect the fuel system and engine for proper opera-
tion.
FAILURE TO START TESTÐ2.5L TBI AND 3.0L
ENGINES
Before proceeding with this test make sure
Testing For Spark At Coil has been performed.
Failure to do this may lead to unnecessary diag-
nostic time and wrong test results.
WARNING: BE SURE TO APPLY PARKING BRAKE
AND/OR BLOCK WHEELS BEFORE PERFORMING
ANY TEST WITH THE ENGINE RUNNING.
(1) Battery voltage must be at least 12.4 volts to
perform test. (2) Crank the engine for 5 seconds while monitoring
the voltage at the coil positive (+) terminal (Fig. 2 or
Fig. 3). If the voltage remains near zero during the
entire period of cranking, refer to Group 14 for On-
Board Diagnostic checks. Also, refer to the DRBII scan
tool and the appropriate Powertrain Diagnostic Proce-
dures manual. These checks will help diagnose prob-
lems with the PCM and auto shutdown relay. (3) If voltage is at near-battery voltage and drops to
zero after 1-2 seconds of cranking, refer to On-Board
Diagnostic in Group 14. Also, refer to the DRBII scan
tool and the appropriate Powertrain Diagnostic Proce-
dures manual. These tests will help check the distribu-
tor reference pickup circuit to the PCM. (4) If voltage remains at near battery voltage during
the entire 5 seconds, with the key off,remove the
PCM 60-way connector. Check the 60-way connector
for any terminals that are pushed out or loose. (5) Remove the connector to coil (+) and connect a
jumper wire between battery (+) and coil (+). (6) Using the special jumper (Fig. 4), momentarily ground terminal #19 of the 60-way connector (Fig.
5). A spark should be generated when the ground is
removed.
(7) If spark is generated, replace the PCM.
(8) If no spark is seen, use the special jumper to
ground the coil (-) terminal directly. (9) If spark is produced, inspect wiring harness for
an open condition.
Fig. 2 Coil TerminalsÐ2.2L TBI, 2.5L TBI and 2.5L MPI Engines
Fig. 3 Coil TerminalsÐ3.0L Engine
Fig. 4 Special Jumper to Ground Coil Negative
Fig. 1 Checking for Spark
8D - 12 IGNITION SYSTEMS Ä

Page 455 of 2438

CHEVROLET PLYMOUTH ACCLAIM 1993 Service Manual (10) If no spark is produced, replace the ignition coil.
POOR PERFORMANCE TEST
To prevent unnecessary diagnostic time and
possible incorrect results, the Testing For Spark
At Coil procedure should be

Page 456 of 2438

CHEVROLET PLYMOUTH ACCLAIM 1993 Service Manual 2.2L TBI, 2.5L TBI, 2.5L MPI AND 3.0L IGNITION SYSTEMSÐSERVICE PROCEDURES
INDEX
page page
Coolant Temperature Sensor ................ 14
Distributor Pick-UpÐ2.2L TBI, 2.5L TBI and 2.5L MPI Engin

2.2L TBI, 2.5L TBI, 2.5L MPI AND 3.0L IGNITION SYSTEMSÐSERVICE PROCEDURES
INDEX
page page
Coolant Temperature Sensor ................ 14
Distributor Pick-UpÐ2.2L TBI, 2.5L TBI and 2.5L MPI Engines ....................... 18
Distributor ServiceÐ3.0L Engine ............. 18
DistributorÐ2.2L TBI, 2.5L TBI and 2.5L MPI Engines .............................. 17
Idle RPM TestÐ2.5L and 3.0L Engines ........ 16
Ignition CoilÐ2.2L TBI, 2.5L TBI and 2.5L MPI Engines ....................... 14 Ignition CoilÐ3.0L Engines
................. 15
Ignition Timing ProcedureÐ2.2L TBI, 2.5L TBI, 2.5L MPI, and 3.0L Engines ............... 16
Manifold Absolute Pressure (MAP) Sensor ServiceÐ2.5L TBI and 3.0L Engines ........ 22
Powertrain Control Module (PCM) ............ 14
Spark Plug Service ....................... 15
POWERTRAIN CONTROL MODULE (PCM)
The powertrain control module (PCM) is located
next to the battery (Fig. 1).
REMOVAL
(1) Remove air cleaner duct or air cleaner assem-
bly. (2) Remove battery.
(3) Remove PCM mounting screws.
(4) Remove 60-way wiring connector from the
PCM. (5) Remove PCM.
INSTALLATION
(1) Connect 60-Way electrical connector to PCM
(Fig. 1). (2) Install PCM. Tighten mounting screws.
(3) Install battery.
(4) Install air cleaner duct or air cleaner assembly.
COOLANT TEMPERATURE SENSOR
On 2.2L TBI, 2.5L TBI and 2.5L MPI (flexible fuel
AA-Body) engines, the coolant temperature sensor is
located behind the ignition coil (Fig. 2). On 3.0L en-
gines the sensor is located next to the thermostat
housing (Fig. 3).
REMOVAL
(1) Drain cooling system until coolant level is below
coolant sensor. Refer to Group 7, Cooling System. (2) Disconnect electrical connector from sensor.
(3) Remove sensor from engine.
INSTALLATION
(1) Install coolant sensor. Tighten 2.2L TBI, 2.5L
TBI or 2.5L MPI engine coolant sensor to 28 N Im (20
ft. lbs.) torque. Tighten the 3.0L engine coolant sensor
to7N Im (60 in. lbs.) torque.
(2) Connect electrical connector to sensor.
(3) Fill cooling system. Refer to Group 7, Cooling
System.
IGNITION COILÐ2.2L TBI, 2.5L TBI AND 2.5L MPI
ENGINES
The ignition coil mounts to the thermostat housing
(Fig. 4).
Fig. 1 Powertrain control module (PCM)
Fig. 2 Coolant Temperature SensorÐ2.2 TBI, 2.5L TBI and 2.5L MPI Engines
8D - 14 IGNITION SYSTEMS Ä

Load next 8 pages

Page: < prev 1-10 ... 417-424 425-432 433-440 441-448 449-456 457-464 465-472 473-480 481-488 ... 2440 next >

fuses park assist carplay differential coolant reservoir navigation update