Coolant Temperature Switch (Or Sensor); Diagnostic Procedures For C4 System - Jeep J-10 Series 1982 Technical & Service Manual

1J-88 FUEL SYSTEMS
(3) Remove retaining screw and unit from
carburetor.
(4) Install replacement motor on carburetor with
retaining screw. Tighten with 25 inch-pounds (2.8 N«m)
torque.
(5) Connect wire connector.
(6) Install air cleaner.
Coolant Temperature Switch (or Sensor)
NOTE: For six-cylinder engines, the coolant temper
ature switch is integral with the intake manifold heater
coolant temperature control switch. The switch is lo
cated at the rear of the intake manifold For four-cylin
der engines, the sensor is located at the left rear of the
cylinder block.
(1) Disconnect wire connector.
(2) Remove switch.
(3) Install replacement switch. Tighten with 72
inch-pounds (7 N«m) torque.
(4) Connect wire connector.
DIAGNOSTIC PROCEDURES FOR C4 SYSTEM
The C4 System should be considered as a possible
source of trouble for engine performance, fuel economy
and exhaust emission complaints only after normal tests
and inspections that would apply to a vehicle without
the C4 system have been performed. An integral self-
diagnostic subsystem within the ECM detects the prob
lems that are most likely to occur.
The diagnostic system will illuminate a test bulb if a
fault exists. If the trouble code test pigtail wire is man
ually connected to ground (located under the dash), the
system will flash a trouble code if a fault has been
detected.
As a routine system test, the test bulb will also be
illuminated when the ignition switch is first turned on
and the engine not started. If the test lead is grounded,
the system will flash a trouble code 12, which indicates
that the diagnostic system is functioning normal (i.e., no
engine rpm voltage to the ECM). This consists of one
flash followed by a pause and then two flashes. After a
longer pause, the code will be repeated two more times.
The cycle will repeat itself until the engine is either
started or the ignition switch turned off. When the en
gine is started, the bulb will remain illuminated for a
few seconds.
If the test lead is grounded with the engine operating
and a fault has been detected by the system, the trouble
code will be flashed three times. If more than one fault
has been detected, the second trouble code will be
flashed three times after the first code is flashed. The
series of code flashes will then be repeated.
A trouble code indicates a problem within a specific
circuit, for example, code 14 indicates a problem in the
coolant temperature sensor circuit. This includes the
coolant temperature sensor, wire harness, and electronic
control module (ECM). The procedure for determining
which of the three is at fault is located in the Trouble
Code 14 chart. For other trouble codes, refer to the
applicable charts.
Because the self-diagnostic subsystem does not detect
all possible faults, the absence of a flashed code does not
always indicate that there is no problem with the sys
tem. To determine this, a system operational test is
necessary. This test should be performed when the test
bulb does not flash a trouble code but the C4 System is
suspected because no other reason can be determined for
a specific complaint. In addition to the test bulb, a dwell
meter, test lamp, digital volt-ohmmeter, tachometer,
vacuum gauge and jumper wires are required to diag
nose system problems. A test lamp rather than a volt
meter should be used when so instructed. Although
most dwell meters should be acceptable, if one causes
a change in engine operation when it is connected to
the mixture control (MC) solenoid dwell pigtail wire
connector, it should not be used. The following models
of older Sun tach/dwell units should not be used: G,
GA, TDT1,2, 5, 216 and 216-1.
The dwell meter, set for the six-cylinder engine scale
and connected to a pigtail wire connector from the mix
ture control (MC) solenoid in the carburetor, is used to
determine the air/fuel mixture dwell. When the dwell
meter is connected, do not allow the terminal to contact
any engine component that is connected to engine
ground. This includes hoses because they may be elec
trically conductive. With a normally operating engine,
the dwell at both idle speed and partial throttle will be
between 10 degrees and 50 degrees and will be varying.
Varying means the pointer continually moves back and
forth across the scale. The amount it varies is not impor
tant, only the fact that it does vary. This indicates closed
loop operation, meaning the mixture is being varied
according to the input voltage to the ECM from the
oxygen sensor. With wide open throttle (WOT) or cold
engine operation, the air/fuel mixture ratio will be fixed
and the pointer will not vary. This is open loop oper
ation, meaning the oxygen sensor output has no effect
on the air/fuel mixture. If there is a question whether or
not the system is in closed loop operation, richening or
leaning the mixture will cause the dwell to vary if the
system is in closed loop operation.
NOTE: Normally, system tests should be performed
with the engine warm (upper radiator hose hot).
Trouble Code Memory
When a fault-is detected in the system, the test bulb
will be illuminated and a trouble code will be set in the