Chrysler RAM TRUCK 2500 1994 Service Manual page 380

• IGNITION SYSTEMS 80 - 23
or punctured, there will be a noticeable spark jump
from the damaged area to the test probe. The cable
running from the ignition coil to the distributor cap
can be checked i n the same manner. Cracked, dam­
aged or faulty cables should be replaced with resis­
tance type cable. This can be identified by the words
ELECTRONIC SUPPRESSION printed on the cable
jacket.
3.9L/5.2L/5.9L Engines: Use an ohmmeter to test
for open circuits, excessive resistance or loose termi-
. nals. Remove the distributor cap from the distributor.
Do n o t remove cables from cap. Remove cable
from spark plug. Connect ohmmeter to spark plug
terminal end of cable and to corresponding electrode
in distributor cap. Resistance should be 250 to 1000
Ohms per inch of cable. I f not, remove cable from dis­
tributor cap tower and connect ohmmeter to the ter­
minal ends of cable. I f resistance is not within
specifications as found i n the Spark Plug Cable Re­
sistance chart, replace the cable. Test all spark plug
cables i n this manner.
S P A R K
P L U G
CABLE RESISTANCE
MINIMUM
M A X I M U M
2 5 0 O h m s Per Inch
1 0 0 0 Ohms Per Inch
3 0 0 0 O h m s Per Foot
1 2 , 0 0 0 O h m s Per Foot
J908D-43
To test ignition coil-to-distributor cap cable, do not
remove the cable from the cap. Connect ohmmeter to
rotor button (center contact) of distributor cap and
terminal at ignition coil end of cable. I f resistance is
not within specifications as found i n the Spark Plug
Cable Resistance chart, remove the cable from the
distributor cap. Connect the ohmmeter to the termi­
nal ends of the cable. I f resistance is not within spec­
ifications as found i n the Spark Plug Cable
Resistance chart, replace the cable. Inspect the igni­
tion coil tower for cracks, burns or corrosion.
For removal and installation of spark plug cables,
refer to Spark Plug Secondary Cables i n the Compo­
nent Removal/Installation section.
OXYGEN SENSOR (02S) TESTS
For an operational description, diagnosis and re­
moval or installation of the 02S, refer to Group 14,
Fuel Systems i n this manual.
0N-B0ARD DIAGNOSTICS (OBD)
F O R IGNITION SYSTEM COMPONENTS
The powertrain control module (PCM) has been
programmed to monitor certain ignition system cir­
cuits:
I f a reference signal is not being detected during
engine cranking from the crankshaft position sensor,
a Diagnostic Trouble Code (DTC) number 11 can be
observed at the Check Engine Lamp.
I f the problem is sensed i n a monitored circuit of­
ten enough to indicate an actual problem, a DTC is
stored. The DTC will be stored i n the PCM memory
for eventual display to the service technician. I f the
problem is repaired or ceases to exist, the PCM can­
cels the DTC after 51 engine starts.
Certain criteria must be met for a DTC to be en­
tered into PCM memory. The criteria may be a spe­
cific range of engine rpm, engine temperature and/or
input voltage to the PCM.
A DTC indicates that the PCM has recognized an
abnormal signal i n a circuit or the system. A DTC
may indicate the result of a failure, but never iden­
tify the failed component directly.
It is possible that a DTC for a monitored circuit
may not be entered into memory even though a mal­
function has occurred. Refer to On-Board Diagnostics
(OBD) i n Group 14, Fuel Systems for additional in­
formation.
ACCESSING DIAGNOSTIC TROUBLE CODES
A stored Diagnostic Trouble Code (DTC) can be dis­
played by cycling the ignition key On-Off-On-Off-On
within three seconds and observing the Malfunction
Indicator Lamp. This lamp was formerly referred to
as the Check Engine Lamp. The lamp is located on
the instrument panel.
They can also be displayed through the use of the
Diagnostic Readout Box (DRB) scan tool. The DRB
connects to the data link connector i n the engine
compartment (Fig. 39). For operation of the DRB, re­
fer to the appropriate Powertrain Diagnostic Proce­
dures service manual.
POWERTRAIN CONTROL
MODULE (PCM) J9414-11
Fig. 39 PCM and Data Link Connector—Typical
EIAMPLES:
• I f the lamp flashes 1 time, pauses and flashes 1
more time, a flashing Diagnostic Trouble Code (DTC)
number 11 is indicated.