1993 DODGE TRUCK Service Repair Manual

14-54 FUEL SYSTEM

• is good, replace the PCM. If terminal/pin-4 has a
short circuit to 12 volts +, correct this condition be­
fore replacing the PCM.

CRANKSHAFT POSITION SENSOR TEST
To perform a complete test of this sensor (Fig. 26)
and its circuitry, refer to the DRB II tester and ap­
propriate Powertrain Diagnostics Procedures manual.
To test the sensor only, refer to the following: (1) Near the rear of the right cylinder head, dis­
connect the sensor pigtail harness connector from the
main wiring harness.

Fig.
26 Crankshaft Position
Sensor—
Typical
(2) Place an ohmmeter across terminals B and C
(Fig. 27). Ohmmeter should be set to lK-to-lOK scale
for this test. The meter reading should be open (no
resistance). Replace sensor if a low resistance is indi­
cated.

VIEW
LOOKING
INTO

CPS
WIRING
CONNECTOR
Fig.
27
Sensor
Wiring
Connector

THROTTLE POSITION SENSOR (TPS) TEST
To perform a complete test of the TPS and its cir­
cuitry, refer to the DRB II tester and appropriate Powertrain Diagnostics Procedures manual. To test
the TPS only, refer to the following:
The TPS can be tested with a digital voltmeter.
The center terminal of the TPS is the output termi­ nal (Fig. 28).

AAANIFOLD
ABSOLUTE
Fig.
28
Throttle
Position
Sensor
(TPS)
Connector—
Typical

With the ignition key in the ON position, check the
TPS output voltage at the center terminal wire of the connector. Check this at idle (throttle plate closed) and at wide open throttle (WOT). At idle, TPS output
voltage should must be greater than 200 millivolts.
At wide open throttle, TPS output voltage must be
less than 4.8 volts. The output voltage should in­
crease gradually as the throttle plate is slowly
opened from idle to WOT.

OXYGEN
(02)
SENSOR HEATING ELEMENT TEST
To perform a complete test of single or dual 02 sen-
sor(s) and circuitry, refer to DRB II tester and appro­
priate Powertrain Diagnostics Procedures manual. To
test the 02 sensor only, refer to the following:
On 3.9L/5.2L/5.9L LDC engines, the single 02 sen­
sor is located on the right exhaust down pipe (Fig.

29).
On 5.9L HDC engines, the dual 02 sensors are
located on each (left and right) exhaust down pipe (Fig. 29).
The 02 heating element can be tested with an ohm­
meter as follows: Disconnect the 02 sensor connector. Connect the
ohmmeter test leads across the white wire terminals
of the sensor connector. Resistance should be be­
tween 5 and 7 ohms. Replace the sensor if the ohm­ meter displays an infinity (open) reading.

•

FUEL
SYSTEM
14 - 55

Fig.
30
Dual
Oxygen
Sensors—5.9L
HDC
Engine
IDLE
AIR
CONTROL
(IAC)
MOTOR
TEST

To perform a complete test of IAC motor (Fig. 81)
and its circuitry, refer to DRB II scan tool and appro­
priate Powertrain Diagnostics Procedures manual. To
test the IAC motor only, special IAC motor exerciser tool number 7558 (Fig. 32) may be used.

CAUTION:
Proper safety precautions must be
taken

when
testing
the IAC
motor,

• Set the parking brake and block the drive wheels
• Route all tester cables away from the cooling fans,
drive belt, pulleys and exhaust components
• Provide proper ventilation while operating the en­
gine
• Always return the engine idle speed to normal be­
fore disconnecting the exerciser tool
(1) With the ignition OFF, disconnect the IAC mo­
tor wire connector at throttle body (Fig. 31).
(2) Plug the exerciser tool (7558) harness connector
into the IAC motor (Fig. 32).
MANIFOLD
ABSOLUTE
Fig.
31 IAC Motor—Typical
Fig.
32 IAC Motor
Testing—
Typical

(3) Connect the red clip of exerciser tool (7558) to
battery positive terminal. Connect the black clip to
negative battery terminal. The red light on the exer­
ciser tool will be illuminated when the exerciser is
properly connected to battery. (4) Start engine.
When the switch is in the HIGH or LOW position,
the light on the exerciser tool will flash. This indi­ cates that voltage pulses are being sent to the IAC
stepper motor.

14
- 56
FUEL
SYSTEM

• (5) Move the switch to the HIGH position. The en­
gine speed should increase. Move the switch to the
LOW position. The engine speed should decrease.
(a) If the engine speed changes while using the
exerciser tool, the IAC motor is functioning prop­
erly. Disconnect the exerciser tool and connect the
IAC stepper motor wire connector to the stepper motor.
(b) If the engine speed does not change, turn the
ignition OFF and proceed to step (6). Do not discon­
nect exerciser from the IAC stepper motor.
(6) Remove the IAC stepper motor from the throt­
tle body.

CAUTION:
When checking IAC motor operation with
the motor removed from
the
throttle
body,
do not
extend
the
pintle (Fig.
33)
more than
6.35 mm (.250
in).
If the pintle is
extended more than
this
amount,
it

may
separate
from
the
IAC stepper
motor.
The
IAC
mo­
tor
must
be
replaced
if the pintle
separates
from
the
motor.
WIRE HARNESS
PINTLE
J9314-116
Fig.
33 IAC Stepper Motor Pintle—Typical (7) With the ignition OFF, cycle the exerciser tool
switch between the HIGH and LOW positions. Ob­
serve the pintle. The pintle should move in-and-out
of the motor.
(a) If the pintle does not move, replace the IAC
motor. Start the engine and test the replacement
motor operation as described in step (5). (b) If the pintle operates properly, check the IAC
motor bore in the throttle body bore for blockage and clean as necessary. Install the IAC motor and
retest. If blockage is not found, refer to the DRB II scan tool and the appropriate Powertrain Diagnos­
tics Procedures service manual.

RELAYS—OPERATION/TESTING
OPERATION
The following operations/tests apply to these
relays only: Automatic Shut Down (ASD) and Fuel Pump. For operations/tests on all other relays, refer
to the appropriate section of this service manual.
These relays are located in the engine compart­
ment (Fig. 34).
DATA LINK CONTROL
CONNECTOR MODULE
J9314-164

Fig.
34 Relay Location The relay terminal numbers from (Fig. 35) can be
found on the bottom of the relay. • Terminal number 30 is connected to battery volt­
age and can be switched or B+ (hot) at all times.
• The center terminal number 87A is connected (a
circuit is formed) to terminal 30 in the de-energized (normally OFF) position.
• Terminal number 87 is connected (a circuit is
formed) to terminal 30 in the energized (ON) posi­
tion. Terminal number 87 then supplies battery volt­ age to the component being operated.
• Terminal number 86 is connected to a switched ( +
)
power source.
• Terminal number 85 is grounded by the power-
train control module (PCM).

TESTING
(1) Remove relay before testing. (2) Using an ohmmeter, perform a resistance test
between terminals 85 and 86. Resistance value (ohms) should be 75 ±5 ohms for resistor equipped
relays.
(3) Connect the ohmmeter between terminals num­
ber 87A and 30. Continuity should be present at this
time.

(4) Connect the ohmmeter between terminals num­
ber 87 and 30. Continuity should not be present at
this time.
(5) Use a set of jumper wires (16 gauge or small­

er).
Connect one jumper wire between terminal num­
ber 85 (on the relay) to the ground side (-) of a 12 Volt power source. (6) Attach the other jumper wire to the positive
side ( +
)
of a 12V power source. Do not connect this
jumper wire to relay at this time.

•
BOTTOM
VIEW

OF RELAY RELAY
CONNECTOR

DE-ENERGIZED
RELAY
ENERGIZED

RELAY
9214-157

Fig.
35 Relay Terminals

CAUTION:
DO NOT
ALLOW
THE
OHMMETER
TO

CONTACT TERMINALS
85 OR 86
DURING THESE

TESTS.
DAMAGE
TO
OHMMETER
MAY
RESULT.

(7) Attach the other jumper wire (12V +) to termi­
nal number 86. This will activate the relay. Continu­
ity should now be present between terminals number
87 and 30. Continuity should not be present between
terminals number 87A and 30.
(8) Disconnect jumper wires from relay and 12
Volt power source.
If continuity or resistance tests did not pass, re­
place relay. If tests passed, refer to Group 8W, Wir­ ing Diagrams for (fuel system) relay wiring schematics and for additional circuit information.

STARTER
MOTOR RELAY TEST
Refer to Group 8A, Battery/Starting/Charging Sys­
tem Diagnostics, for starter motor relay testing.

FUEL INJECTOR TEST
Disconnect the fuel injector wire harness connector
from the injector (Fig. 36). Place an ohmmeter across
the injector terminals. Resistance reading should be approximately 14.5 ohms ±1.2 ohms at 20°C (68°F).
Proceed to following Fuel Injector diagnosis chart.
FUEL INJECTOR

HARNESS
CONNECTORS
FUEL
INJECTOR
J9214-30

Fig.
36
Fuel
Injector Wiring
Connector—
Typical

FUEL PUMP
PRESSURE
TEST
Refer to Fuel Pump Pressure Test in the Fuel De­
livery System section of this group.

14 - 58
FUEL
SYSTEM
• INJECTOR DIAGNOSIS-VEHICLE RUNS ROUGH AND/OR HAS A
MISS

DO PRELIMINARY INSPECTION OF DISTRIBUTOR CAP,
IGNITION

CABLES
SPARK
PLUGS,
AND

CHECK
FOR VACUUM
LEAKS.
START VEHICLE, PULL THE

ELECTRICAL
CONNECTORS OFF
THE INJECTORS ONE AT A TIME
TO DETERMINE
WHICH
CYLINDER
IS
NOT FIRING.

REPLACE
THE INJECTOR -NO •

CHECK
POWER FEED AND
GROUND CIRCUITS BETWEEN POWERTRAIN CONTROL MODULE
AND THE INJECTOR CONNECTOR.
REFER
TO WIRING SCHEMATIC
FOR COLOR CODES AND PIN
TERMINAL NUMBERS. - NO-
YES

TEST THE VEHICLE
WITH
THE DRB II

SCAN
TOOL
NO

REPAIR
OR REPLACE THE WIRING
HARNESS
AS NECESSARY.

REPLACE
INJECTOR IF VISUALLY

PLUGGED
AT INJECTOR FUEL INLET.

REPLACE
FUEL RAIL IF VISUALLY

PLUGGED
OR RESTRICTED AT INJECTOR DELIVERY COUPLING. -NO

REPLACE
INJECTOR •NO-TEST THE INJECTOR RESISTANCE
USING AN OHMMETER
ACROSS

THE INJECTOR TERMINALS
WITH

THE INJECTOR CONNECTOR
REMOVED.

PLACE
A 12
VOLT
TEST LAMP

ACROSS
THE INJECTOR

ELECTRICAL
CONNECTOR

TERMINALS.
OBSERVE THE TEST LAMP WHILE CRANKING THE

ENGINE.

CIRCUIT IS OK. CHECK FOR FUEL DELIVERY AT SUSPECT INJECTOR

BY
REMOVING THE INJECTOR FROM THE RAIL AND OBSERVING
FOR FUEL AND/OR RESTRICTIONS IN THE RAIL OR INJECTOR FUEL INLET.

WITH
INJECTOR REMOVED FROM
THE FUEL RAIL, CONNECT A 12V
SOURCE
TO ONE TERMINAL ON
THE INJECTOR CONNECTOR AND

A
GROUND WIRE TO THE OTHER
TERMINAL. THE INJECTOR SHOULD "CLICK" EACH TIME THE GROUND WIRE IS CONNECTED
AND DISCONNECTED TO THE TERMINAL.

J9314-114

•

FUEL SYSTEM
14 - 59
fill
DHADn
HIAf5MflCTipQ
/f|Rn

The powertrain control module (PCM) has been
programmed to monitor many different circuits of the
fuel injection system. If a problem is sensed in a monitored circuit often enough to indicate an actual
problem, a diagnostic trouble code (DTC) is stored.
The DTC will be stored in the PCM memory for eventual display to the service technician. If 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 diagnostic trou­
ble code (DTC) to be entered into PCM memory. The criteria may be a specific range of engine rpm, en­
gine temperature and/or input voltage to the PCM.
It is possible that a DTC for a monitored circuit
may not be entered into memory even though a mal­
function has occurred. This may happen because one
of the DTC criteria for the circuit has not been met. Example: assume that one of the criteria for the
MAP sensor circuit is that the engine must be oper­ ating between 750 and 2000 rpm to be monitored for
a DTC. If the MAP sensor output circuit shorts to
ground when the engine rpm is above 2400 rpm, a 0
volt input will be seen by the PCM. A DTC will not
be entered into memory because the condition does not occur within the specified rpm range.
A DTC indicates that the powertrain control mod­
ule (PCM) has recognized an abnormal signal in a
circuit or the system. A DTC may indicate the result
of a failure, but never identify the failed component
directly.
There are several operating conditions that the
PCM does not monitor and set a DTC for. Refer to
the following Monitored Circuits and Non-Monitored Circuits in this section.

MONITORED
CIRCUITS
The powertrain control module (PCM) can detect
certain problems in the fuel injection system.
Open or Shorted Circuit - The PCM can deter­
mine if sensor output (which is the input to PCM) is
within proper range. It also determines if the circuit is open or shorted.
Output Device Current Flow - The PCM senses
whether the output devices are hooked up.
If there is a problem with the circuit, the PCM
senses whether the circuit is open, shorted to ground
(-), or shorted to
(
+
)
voltage.
Oxygen Sensor - The PCM can determine if the
oxygen sensor is switching between rich and lean.
This is, once the system has entered Closed Loop. Re­ fer to Open Loop/Closed Loop Modes Of Operation in
the Component Description/System Operation section
for an explanation of Closed (or Open) Loop opera­ tion.
NON-MONITORED CIRCUITS

The PCM does not monitor the following circuits,
systems or conditions that could have malfunctions
that result in driveability problems. A diagnostic trouble code (DTC) may not be displayed for these
conditions.
Fuel Pressure: Fuel pressure is controlled by the
vacuum assisted fuel pressure regulator. The PCM
cannot detect a clogged fuel pump inlet filter, clogged
in-line fuel filter, or a pinched fuel supply or return

line.
However, these could result in a rich or lean
condition causing an oxygen sensor DTC to be stored in the PCM.
Secondary Ignition Circuit: The PCM cannot de­
tect an inoperative ignition coil, fouled or worn spark

plugs,
ignition cross firing, or open circuited spark
plug cables.
Engine Timing: The PCM cannot detect an incor­
rectly indexed timing chain, camshaft sprocket or crankshaft sprocket. The PCM also cannot detect an
incorrectly indexed distributor. However, these could
result in a rich or lean condition causing an oxygen
sensor DTC to be stored in the PCM.
Cylinder Compression: The PCM cannot detect
uneven, low, or high engine cylinder compression.
Exhaust System: The PCM cannot detect
a

plugged, restricted or leaking exhaust system.
Fuel Injector Malfunctions: The PCM cannot de­
termine if the fuel injector is clogged, or the wrong injector is installed. However, these could result in a
rich or lean condition causing an oxygen sensor DTC
to be stored in the PCM.
Excessive Oil Consumption: Although the PCM
monitors exhaust stream oxygen content through ox­
ygen sensor (closed loop), it cannot determine exces­ sive oil consumption.
Throttle Body Air Flow: The PCM cannot detect
a clogged or restricted air cleaner inlet or air filter
element.
Evaporative System: The PCM will not detect a
restricted, plugged or loaded EVAP canister. Vacuum Assist: Leaks or restrictions in the vac­
uum circuits of vacuum assisted engine control sys­
tem devices are not monitored by the PCM. However, a vacuum leak at the MAP sensor will be monitored
and a diagnostic trouble code (DTC) will be gener­
ated by the PCM.
Powertrain Control Module (PCM) System
Ground: The PCM cannot determine a poor system
ground. However, a DTC may be generated as a re­
sult of this condition.
Powertrain Control Module (PCM) Connector
Engagement: The PCM cannot determine spread or
damaged connector pins. However, a DTC may be generated as a result of this condition.

14 - SO
FUEL
SYSTEM

•
HIGH
AND LOW
LIMITS

The powertrain control module (PCM) compares in­
put signal voltages from each input device. It will es­
tablish high and low limits that are programmed into it for that device. If the input voltage is not
within specifications and other diagnostic trouble code (DTC) criteria are met, a DTC will be stored in
memory. Other DTC criteria might include engine
rpm limits or input voltages from other sensors or switches. The other inputs might have to be sensed
by the PCM when it senses a high or low input volt­ age from the control system device in question.
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 II (DRB II scan tool). The
DRB II connects to the data link connector in the ve­
hicle (Fig. 37). For operation of the DRB II, refer to
the appropriate Powertrain Diagnostic Procedures service manual.
TORQUE CONVERTER
CLUTCH RELAY
A/C
CLUTCH RELAY
.
STARTER RELAY

AUTO
SHUTDOWN RELAY FUEL PUMP RELAY POWERTRAIN
DATA LINK CONTROL
CONNECTOR MODULE
J9314-164

Fig.
37
Data
Link
Connector
Location—Typical
EXAMPLES

• If the lamp flashes 4 times, pauses and flashes 1
more time, a diagnostic trouble code (DTC) number
41 is indicated.
• If the lamp flashes 4 times, pauses and flashes 6
more times, a diagnostic trouble code (DTC) number
46 is indicated. Refer to the Diagnostic Trouble Code (DTC) charts
for DTC identification. If the problem is repaired or ceases to exist, the
powertrain control module (PCM) cancels the DTC after 51 engine starts.
Diagnostic trouble codes indicate the results of a
failure, but never identify the failed component di­
rectly. The circuits of the data link connector are shown
in (Fig. 38).
J9214-20
D-1

GROUND

D-2 Im/c
D-3
SCI
TRANS

D-4
SCI
RECEIVE

D-5
IGNITION

D-6
NOT
USED

Fig.
38
Data
Link
Connector
Schematic

ERASING TROUBLE CODES The DRB II scan tool must be used to erase a di­
agnostic trouble code (DTC). Refer to the appropriate
Powertrain Diagnostic Procedures service manual for operation of the DRB II scan tool.

DRB
II
SCAN
TOOL
For operation of the DRB II scan tool, refer to the
appropriate Powertrain Diagnostic Procedures ser­
vice manual.

DIAGNOSTIC TROUBLE CODE
(DTC) On the following pages, a list of diagnostic trouble
codes is provided for all gas powered engines. A DTC indicates that the powertrain control module (PCM)
has recognized an abnormal signal in a circuit or the system. A DTC may indicate the result of a failure,
but never identify the failed component directly.

•

FUEL
SYSTEM
14-61 DIAGNOSTIC TROUBLE CODE {DTC) DESCRIPTION
Diagnostic

Trouble
Code DRB II
Display
Description of Trouble Code Condition
11
No
Crank
Reference
Signal at PCM No distributor reference signal detected during engine cranking.

13+**
No Change in
AAAP

From
Start
to Run No variation in MAP sensor signal is detected.
No difference is recognized between the engine
MAP
reading and
the barometric pressure reading at start up.

14+**
MAP
Voltage Too Low
or

MAP
Voltage Too High
MAP
sensor input below minimum acceptable voltage.
MAP sensor input above maximum acceptable voltage.

15**
No Vehicle Speed
Sensor Signal No speed sensor signal detected during road load conditions.

17
Engine is Cold Too Long Engine coolant temperature remains below normal operating temperatures
during vehicle travel (thermostat).

21**
O2
Signal Stays at
Center or

Oo
Signal Shorted to
Voltage Neither rich or lean condition
is
detected from the oxygen sensor input.
Oxygen sensor input voltage maintained above normal operating range.

22+**
ECT
Sensor
Voltage
Too
Low or

ECT
Sensor
Voltage
Too
High Coolant temperature sensor input below the minimum acceptable voltage.
Coolant temperature sensor input above the maximum acceptable voltage.

23
Charge Air Temperature
Sensor Voltage High or
Charge Air Temperature Sensor Voltage Low Charge Air Temperature Sensor input above/below acceptable minimum.

24+**
Throttle Position
Sensor Voltage High or
Throttle Position Sensor Voltage
Low
Throttle position sensor
(TPS)
input above the maximum acceptable voltage.
Throttle position sensor
(TPS)
input below the minimum acceptable voltage.

**
Check Engine Lamp ON (California only)
+ Check Engine Lamp ON J9314-126