wiring MERCEDES-BENZ SPRINTER 2006 Service Manual

rate and boost pressure are adjusted to the actual
injection quantity.
²Injection valve quantity drift compensation in
full load range: this function is to limit the maximum
injection quantity for engine protection. The injection
quantity signal is compared to the injection quantity
calculated from the oxygen sensor signal and MAF
signal. If the comparison shows that the actual injec-
tion quantity is too high, it is limited to the maxi-
mum permissible injection quantity
²Air-fuel ratio controlled smoke limiter (full load):
the smoke limiter limits the injection quantity on the
basis of the air-fuel ratio permissible at the smoke
limit depending on the measure mass air flow and
the calculated EGR rate. As a consequence, the gen-
eration of smoke due to an excess injection quantity
is avoided under all operating conditions. At the
same time, the oxygen sensor signal is used to
ensure that the air-fuel ratio is adjusted accordingly
A function referred to as air flow sensor drift com-
pensation detects and corrects the possible drifting of
the MAF sensor by comparing the air mass measured
by the MAF with the projected air mass as it is cal-
culated by the ECM in consideration of various influ-
encing conditions. It is the air flow drift
compensation that gives the MAF air mass measure-
ment the precision needed to use it for the function
mentioned above. The high precision of the MAF
measurement enables the calculation of the actual
injection quantity from the measured air mass and
from the oxygen sensor signal in order to correct
injection quantity. The MAF signal can also be used
as a input parameter for the smoke limiter.
REMOVAL
(1) Disconnect the negative battery cable.
(2) Disconnect the ECM harness connectors (Fig.
4).
(3) Grasp ECM and pull down firmly to release
ECM from the retaining bracket tensioning springs
(Fig. 4).
INSTALLATION
NOTE: THE ECM MUST BE PROGRAMMED TO SUP-
PORT THE VEHICLE OPTIONS PACKAGE.
(1) Position the ECM into the guide of the retain-
ing bracket (Fig. 4).
(2) Carefully push the ECM in to the bracket until
the bracket tensioning springs engage (Fig. 4).
(3) Connect the ECM wiring harness connectors
(Fig. 4).
(4) Connect negative battery cable.
TRANSMISSION CONTROL
MODULE
DESCRIPTION
The transmission control module (TCM) receives,
processes and sends various digital and analog sig-
nals related to the automatic transmission. In addi-
tion, it processes information received from other
vehicle systems, such as engine torque and speed,
accelerator pedal position, wheel speed, kick-down
switch, traction control information, etc.
The TCM is located under the driver's seat and is
connected to other control modules via a CAN bus. It
controls all shift functions to achieve smooth shift
comfort in all driving situations considering:
²Vehicle speed.
²Transmission status.
Fig. 4 ECM
1 - BRACKET
2 - ECM
3 - BRACKET TENSIONING SPRINGS
8E - 6 ELECTRONIC CONTROL MODULESVA

(3) Using a voltmeter connected to the battery
posts (see the instructions provided by the manufac-
turer of the voltmeter), measure the open-circuit volt-
age (Fig. 5).
See the Open-Circuit Voltage Table. This voltage
reading will indicate the battery state-of-charge, but
will not reveal its cranking capacity. If a battery has
an open-circuit voltage reading of 12.4 volts or
greater, it may be load tested to reveal its cranking
capacity (Refer to 8 - ELECTRICAL/BATTERY SYS-
TEM/BATTERY - STANDARD PROCEDURE).
OPEN CIRCUIT VOLTAGE TABLE
Open Circuit Voltage Charge Percentage
11.7 volts or less 0%
12.0 volts 25%
12.2 volts 50%
12.4 volts 75%
12.6 volts or more 100%
STANDARD PROCEDURE - IGNITION - OFF
DRAW TEST
The term Ignition-Off Draw (IOD) identifies a nor-
mal condition where power is being drained from the
battery with the ignition switch in the Off position. A
normal vehicle electrical system will draw from five
to thirty-five milliamperes (0.005 to 0.035 ampere)
with the ignition switch in the Off position, and all
non-ignition controlled circuits in proper working
order. Up to thirty-five milliamperes are needed to
enable the memory functions for the Powertrain Con-
trol Module (PCM), digital clock, electronically tuned
radio, and other modules which may vary with the
vehicle equipment.A vehicle that has not been operated for approxi-
mately twenty days, may discharge the battery to an
inadequate level. When a vehicle will not be used for
twenty days or more (stored), remove the IOD fuse
from the fuseblock. This will reduce battery discharg-
ing.
Excessive IOD can be caused by:
²Electrical items left on.
²Faulty or improperly adjusted switches.
²Faulty or shorted electronic modules and compo-
nents.
²An internally shorted generator.
²Intermittent shorts in the wiring.
If the IOD is over thirty-five milliamperes, the
problem must be found and corrected before replac-
ing a battery. In most cases, the battery can be
charged and returned to service after the excessive
IOD condition has been corrected.
(1) Verify that all electrical accessories are off.
Turn off all lamps, remove the ignition key, and close
all doors. If the vehicle is equipped with an illumi-
nated entry system or an electronically tuned radio,
allow the electronic timer function of these systems
to automatically shut off (time out). This may take
up to three minutes.
(2) Determine that the underhood lamp is operat-
ing properly, then disconnect the lamp wire harness
connector or remove the lamp bulb.
(3) Disconnect the battery negative cable.
(4) Set an electronic digital multi-meter to its
highest amperage scale. Connect the multi-meter
between the disconnected battery negative cable ter-
minal clamp and the battery negative terminal post.
Make sure that the doors remain closed so that the
illuminated entry system is not activated. The multi-
meter amperage reading may remain high for up to
three minutes, or may not give any reading at all
while set in the highest amperage scale, depending
upon the electrical equipment in the vehicle. The
multi-meter leads must be securely clamped to the
battery negative cable terminal clamp and the bat-
tery negative terminal post. If continuity between the
battery negative terminal post and the negative cable
terminal clamp is lost during any part of the IOD
test, the electronic timer function will be activated
and all of the tests will have to be repeated.
(5) After about three minutes, the high-amperage
IOD reading on the multi-meter should become very
low or nonexistent, depending upon the electrical
equipment in the vehicle. If the amperage reading
remains high, remove and replace each fuse or circuit
breaker in the Fuse Blocks, one at a time until the
amperage reading becomes very low, or nonexistent.
Refer to the appropriate wiring information in this
service manual for complete fuseblock fuse, circuit
breaker, and circuit identification. This will isolate
Fig. 5 Testing Open Circuit Voltage
8F - 10 BATTERY SYSTEMVA

each circuit and identify the circuit that is the source
of the high-amperage IOD. If the amperage reading
remains high after removing and replacing each fuse
and circuit breaker, disconnect the wire harness from
the generator. If the amperage reading now becomes
very low or nonexistent, refer to Charging System for
the proper charging system diagnosis and testing
procedures. After the high-amperage IOD has been
corrected, switch the multi-meter to progressively
lower amperage scales and, if necessary, repeat the
fuse and circuit breaker remove-and-replace process
to identify and correct all sources of excessive IOD. It
is now safe to select the lowest milliampere scale of
the multi-meter to check the low-amperage IOD.
CAUTION: Do not open any doors, or turn on any
electrical accessories with the lowest milliampere
scale selected, or the multi-meter may be damaged.
(6) Observe the multi-meter reading. The low-am-
perage IOD should not exceed thirty-five milliam-
peres (0.035 ampere). If the current draw exceeds
thirty-five milliamperes, isolate each circuit using the
fuse and circuit breaker remove-and-replace process
in Step 5. The multi-meter reading will drop to
within the acceptable limit when the source of the
excessive current draw is disconnected. Repair this
circuit as required; whether a wiring short, incorrect
switch adjustment, or a component failure is at fault.
STANDARD PROCEDURE - USING MICRO 420
BATTERY TESTER
Always use the Micro 420 Instruction Manual that
was supplied with the tester as a reference. If theInstruction Manual is not available the following pro-
cedure can be used:
WARNING: ALWAYS WEAR APPROPRIATE EYE
PROTECTION AND USE EXTREME CAUTION WHEN
WORKING WITH BATTERIES.
BATTERY TESTING
(1) If testing the battery OUT-OF-VEHICLE, clean
the battery terminals with a wire brush before test-
ing. If the battery is equipped with side post termi-
nals, install and tighten the supplied lead terminal
stud adapters. Do not use steel bolts. Failure to prop-
erly install the stud adapters, or using stud adapters
that are dirty or worn-out may result in false test
readings.
(2) If testing the battery IN-THE-VEHICLE, make
certain all of the vehicle accessory loads are OFF,
including the ignition.The preferred test position
is at the battery terminal. If the battery is not
accessible, you may test using both the positive and
negative jumper posts. Select TESTING AT JUMPER
POST when connecting to that location.
(3) Connect the tester (Fig. 6) to the battery or
jumper posts, the red clamp to positive (+) and the
black clamp to negative (±).
NOTE: Multiple batteries connected in parallel must
have the ground cable disconnected to perform a
battery test. Failure to disconnect may result in
false battery test readings.
(4) Using the ARROW key selectinoroutof vehi-
cle testing and press ENTER to make a selection.
(5) If not selected, choose the Cold Cranking Amp
(CCA) battery rating. Or select the appropriate bat-
tery rating for your area (see menu). The tester will
then run its self programmed test of the battery and
display the results. Refer to the test result table
noted below.
CAUTION: If REPLACE BATTERY is the result of the
test, this may mean a poor connection between the
vehicle's cables and battery exists. After discon-
necting the vehicle's battery cables from the bat-
tery, retest the battery using the OUT-OF-VEHICLE
test before replacing.
(6) While viewing the battery test result, press the
CODE button and the tester will prompt you for the
last 4 digits of the VIN. Use the UP/DOWN arrow
buttons to scroll to the correct character; then press
ENTER to select and move to the next digit. Then
press the ENTER button to view the SERVICE
CODE. Pressing the CODE button a second time will
return you to the test results.
Fig. 6 Micro 420 Battery Tester
VABATTERY SYSTEM 8F - 11

INSTALLATION
(1) Install the battery hold down brackets.
(2) Install the two nuts that secure the battery
hold down brackets to the battery tray. Tighten to 70
in. lbs.
BATTERY CABLES
DESCRIPTION
The battery cables are large gauge, stranded cop-
per wires sheathed within a heavy plastic or syn-
thetic rubber insulating jacket. The wire used in the
battery cables combines excellent flexibility and reli-
ability with high electrical current carrying capacity.
The battery cables cannot be repaired and, if dam-
aged or faulty they must be replaced. Both the bat-
tery positive and negative cables are available for
service replacement only as a unit with the battery
positive cable wire harness or the battery negative
cable wire harness, which may include portions of
the wiring circuits for the generator and other com-
ponents on some models.
The battery cables feature a stamped brass clamp-
ing type female battery terminal crimped onto one
end of the battery cable wire and then solder-dipped.
A square headed pinch-bolt and hex nut are installed
at the open end of the female battery terminal clamp.
The battery positive cable also includes a red molded
rubber protective cover for the female battery termi-
nal clamp. Large eyelet type terminals are crimped
onto the opposite end of the battery cable wire and
then solder-dipped. The battery positive cable wires
have a red insulating jacket to provide visual identi-
fication and feature a larger female battery terminal
clamp to allow connection to the larger battery posi-
tive terminal post. The battery negative cable wires
have a black insulating jacket and a smaller female
battery terminal clamp.
OPERATION
The battery cables connect the battery terminal
posts to the vehicle electrical system. These cables
also provide a return path for electrical current gen-
erated by the charging system for restoring the volt-
age potential of the battery. The female battery
terminal clamps on the ends of the battery cable
wires provide a strong and reliable connection of the
battery cable to the battery terminal posts. The ter-
minal pinch bolts allow the female terminal clamps
to be tightened around the male terminal posts on
the top of the battery. The eyelet terminals secured
to the ends of the battery cable wires opposite the
female battery terminal clamps provide secure and
reliable connection of the battery to the vehicle elec-
trical system.
DIAGNOSIS AND TESTING - BATTERY CABLES
A voltage drop test will determine if there is exces-
sive resistance in the battery cable terminal connec-
tions or the battery cables. If excessive resistance is
found in the battery cable connections, the connec-
tion point should be disassembled, cleaned of all cor-
rosion or foreign material, then reassembled.
Following reassembly, check the voltage drop for the
battery cable connection and the battery cable again
to confirm repair.
When performing the voltage drop test, it is impor-
tant to remember that the voltage drop is giving an
indication of the resistance between the two points at
which the voltmeter probes are attached.EXAM-
PLE:When testing the resistance of the battery pos-
itive cable, touch the voltmeter leads to the battery
positive cable terminal clamp and to the battery pos-
itive cable eyelet terminal at the starter solenoid
B(+) terminal stud. If you probe the battery positive
terminal post and the battery positive cable eyelet
terminal at the starter solenoid B(+) terminal stud,
you are reading the combined voltage drop in the
battery positive cable terminal clamp-to-terminal
post connection and the battery positive cable.
VOLTAGE DROP TEST
WARNING: IF THE BATTERY SHOWS SIGNS OF
FREEZING, LEAKING, LOOSE POSTS, OR LOW
ELECTROLYTE LEVEL, DO NOT TEST, ASSIST-
BOOST, OR CHARGE. THE BATTERY MAY ARC
INTERNALLY AND EXPLODE. PERSONAL INJURY
AND/OR VEHICLE DAMAGE MAY RESULT.
WARNING: EXPLOSIVE HYDROGEN GAS FORMS IN
AND AROUND THE BATTERY. DO NOT SMOKE,
USE FLAME, OR CREATE SPARKS NEAR THE BAT-
TERY. PERSONAL INJURY AND/OR VEHICLE DAM-
AGE MAY RESULT.
WARNING: THE BATTERY CONTAINS SULFURIC
ACID, WHICH IS POISONOUS AND CAUSTIC. AVOID
CONTACT WITH THE SKIN, EYES, OR CLOTHING.
IN THE EVENT OF CONTACT, FLUSH WITH WATER
AND CALL A PHYSICIAN IMMEDIATELY. KEEP OUT
OF THE REACH OF CHILDREN.
WARNING: IF THE BATTERY IS EQUIPPED WITH
REMOVABLE CELL CAPS, BE CERTAIN THAT EACH
OF THE CELL CAPS IS IN PLACE AND TIGHT
BEFORE THE BATTERY IS RETURNED TO SER-
VICE. PERSONAL INJURY AND/OR VEHICLE DAM-
AGE MAY RESULT FROM LOOSE OR MISSING
CELL CAPS.
8F - 14 BATTERY SYSTEMVA

volt, clean and tighten the battery negative cable
eyelet terminal connection to the engine block.
Repeat the test. If the reading is still above 0.2 volt,
replace the faulty battery negative cable.
REMOVAL
(1) Turn the ignition switch to the Off position. Be
certain that all electrical accessories are turned off.
(2) Disconnect and isolate the remote battery neg-
ative cable terminal.
(3) One at a time, trace and disconnect the battery
cable retaining pushpins, fasteners and routing clips
until the cables are free from the vehicle.
(4) Feed the battery cable assembly out of the
vehicle.
INSTALLATION
(1) Position the battery cable in the vehicle.
(2) One at a time, install the battery cable retain-
ing pushpins, fasteners and routing clips until the
cable is installed exactly in the factory installed loca-
tion in the vehicle. Refer to the Wiring Diagram sec-
tion of the service manual for reference.
(3) Connect the battery negative cable terminal.
BATTERY TRAY
DESCRIPTION
The battery is mounted in a stamped steel battery
tray located in the left front corner of the engine
compartment. The battery tray is secured with bolts
to the left front wheelhouse inner steel panel. A hole
in the bottom of the battery tray is fitted with aformed drain tube. A second hole in the bottom of the
tray is fitted with a battery temperature sensor.
OPERATION
The battery tray provides a mounting location and
support for the vehicle battery. The battery tray sup-
port supports the battery tray and provides an
anchor point for the inboard battery hold down hard-
ware. The battery tray and the battery hold down
hardware combine to secure and stabilize the battery
in the engine compartment, which prevents battery
movement during vehicle operation. Unrestrained
battery movement during vehicle operation could
result in damage to the vehicle, the battery or both.
The battery tray drain tube directs spilled water or
electrolyte from a leaking battery to the ground
through another hole in the front extension of the
left front wheelhouse inner panel.
REMOVAL
(1) Remove the battery from the battery tray.
(Refer to 8 - ELECTRICAL/BATTERY SYSTEM/BAT-
TERY - REMOVAL).
(2) Remove the battery temperature sensor from
the battery tray. (Refer to 8 - ELECTRICAL/CHARG-
ING/BATTERY TEMPERATURE SENSOR -
REMOVAL).
(3) Remove the bolts that secure the battery tray
to the battery tray support.
(4) Remove the battery tray from the vehicle.
INSTALLATION
(1) Clean and inspect the battery tray. (Refer to 8 -
ELECTRICAL/BATTERY SYSTEM - CLEANING).
(2) Position the battery tray onto the battery tray
support.
(3) Install and tighten the bolts that secure the
battery tray to the battery tray support. Tighten the
screws to 11.8 N´m (105 in. lbs.).
(4) Install the battery temperature sensor onto the
battery tray. (Refer to 8 - ELECTRICAL/CHARGING/
BATTERY TEMPERATURE SENSOR - INSTALLA-
TION).
(5) Install the battery onto the battery tray. (Refer
to 8 - ELECTRICAL/BATTERY SYSTEM/BATTERY -
INSTALLATION).
Fig. 12 Test Ground Circuit Resistance - Typical
1 - VOLTMETER
2 - BATTERY
3 - ENGINE GROUND
8F - 16 BATTERY SYSTEMVA

INSTALLATION
(1) Raise and support vehicle.
(2) Position generator to engine.
(3) Install 4 generator mounting bolts (Fig. 1).
Refer to Torque Specifications.
(4) Connect field terminal connector at rear of gen-
erator.
(5) Install battery output cable and nut to B+ ter-
minal at top of generator. Refer to Torque Specifica-
tions.
(6) Install protective plastic cover to B+ stud at
top of generator.
(7) Lower vehicle.
CAUTION: Never force a belt over a pulley rim
using a screwdriver. The synthetic fiber of the belt
can be damaged.
CAUTION: When installing a serpentine accessory
drive belt, the belt MUST be routed correctly. Thewater pump will be rotating in the wrong direction if
the belt is installed incorrectly, causing the engine
to overheat. Refer to belt routing label in engine
compartment, or refer to Belt Schematics in Cooling
System.
(8) Install generator drive belt. Refer to Cooling
System for procedure.
(9) Connect negative battery cable.
(10) Check charging system for proper operation.
GENERATOR DECOUPLER
PULLEY
DESCRIPTION
The generator decoupler is used only with
certain engines.The decoupler is used in place of
the standard generator drive pulley (Fig. 2).
OPERATION
The generator decoupler is used only with
certain engines.The decoupler (Fig. 2) is a one-way
clutch designed to help reduce belt tension fluctua-
tion, vibration, reduce fatigue loads, improve belt life,
reduce hubloads on components, and reduce noise.
Dry operation is used (no grease or lubricants). The
decoupler is not temperature sensitive and also has a
low sensitivity to electrical load. The decoupler is a
non-serviceable item and is to be replaced as an
assembly.
Fig. 1 GENERATOR MOUNTING - 2.7L DIESEL
1 - GENERATOR
2 - DRIVE BELT
3 - MOUNTING BOLTS (4)
4 - GENERATOR WIRING HARNESS
Fig. 2 GENERATOR DECOUPLER PULLEY
VACHARGING SYSTEM 8F - 19

starter pinion gear to spin faster than the pinion
shaft. When the driver releases the ignition switch to
the On position, the starter relay coil is de-energized.
This causes the relay contacts to open. When the
relay contacts open, the starter solenoid plunger
hold-in coil is de-energized.
When the solenoid plunger hold-in coil is de-ener-
gized, the solenoid plunger return spring returns the
plunger to its relaxed position. This causes the con-
tact disc to open the starter feed circuit, and the shift
lever to disengage the overrunning clutch and pinion
gear from the starter ring gear.DIAGNOSIS AND TESTING - STARTING SYS-
TEM
The battery, starting, and charging systems oper-
ate in conjunction with one another, and must be
tested as a complete system. For correct starting/
charging system operation, all of the components
involved in these 3 systems must perform within
specifications.
Starting System Diagnosis
CONDITION POSSIBLE CAUSE CORRECTION
STARTER FAILS TO
OPERATE.1. Battery discharged or
faulty.1. Refer to Battery. Charge or replace battery, if re-
quired.
2. Starting circuit wiring
faulty.2. Refer to 8, Wiring Diagrams. Test and repair starter
feed and/or control circuits, if required.
3. Starter relay faulty. 3. Refer to Starter Relay in Diagnosis and Testing. Re-
place starter relay if required.
4. Ignition switch faulty. 4. Refer to Ignition Switch and Key Lock Cylinder. Re-
place ignition switch if required.
5. Clutch pedal position
switch faulty.5. Refer to Clutch Pedal Position Switch.
6. Park/Neutral position
switch faulty or misad-
justed.6. Refer to Park/Neutral Position Switch. Replace park/
neutral position switch if required.
7. Starter solenoid faulty. 7. Refer to Starter Motor. Replace starter motor assem-
bly if required.
8. Starter motor faulty. 8. If all other starting system components and circuits
test OK, replace starter motor.
STARTER ENGAGES,
FAILS TO TURN EN-
GINE.1. Battery discharged or
faulty.1. Refer to Battery. Charge or replace battery if re-
quired.
2. Starting circuit wiring
faulty.2. Refer to 8, Wiring Diagrams. Test and repair starter
feed and/or control circuits if required.
3. Starter motor faulty. 3. If all other starting system components and circuits
test OK, replace starter motor assembly.
4. Engine seized. 4. Refer to Engine Diagnosis in the Diagnosis and Test-
ing section of 9, Engine.
STARTER ENGAGES,
SPINS OUT BEFORE
ENGINE STARTS.1. Starter ring gear
faulty.1. Refer to Starter Motor Removal and Installation. Re-
move starter motor to inspect starter ring gear. Replace
starter ring gear if required.
2. Starter motor faulty. 2. If all other starting system components and circuits
test OK, replace starter motor assembly.
VASTARTING SYSTEM 8F - 29

Starting System Diagnosis
CONDITION POSSIBLE CAUSE CORRECTION
STARTER DOES NOT
DISENGAGE.1. Starter motor improp-
erly installed.1. Refer to Starter Motor Removal and Installation.
Tighten starter mounting hardware to correct torque
specifications.
2. Starter relay faulty. 2. Refer to Starter Relay Diagnosis and Testing. Re-
place starter relay if required.
3. Ignition switch faulty. 3. Refer to Ignition Switch and Key Lock Cylinder. Re-
place ignition switch if required.
4. Starter motor faulty. 4. If all other starting system components and circuits
test OK, replace starter motor.
INSPECTION
For complete starter wiring circuit diagrams, refer
to 8, Wiring Diagrams. Before removing any unit
from starting system for repair or diagnosis, perform
the following inspections:
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, REFER TO 8, PASSIVE RESTRAINT SYS-
TEMS, BEFORE ATTEMPTING ANY STEERING
WHEEL, STEERING COLUMN, OR INSTRUMENT
PANEL COMPONENT DIAGNOSIS OR SERVICE.
FAILURE TO TAKE THE PROPER PRECAUTIONS
COULD RESULT IN ACCIDENTAL AIRBAG DEPLOY-
MENT AND POSSIBLE PERSONAL INJURY.
²Battery- Visually inspect battery for indica-
tions of physical damage and loose or corroded cable
connections. Determine state-of-charge and cranking
capacity of battery. Charge or replace battery if
required. Refer toBatteryin 8, Battery.
²Ignition Switch- Visually inspect ignition
switch for indications of physical damage and loose
or corroded wire harness connections. Refer toIgni-
tion Switch and Key Lock Cylinder.
²Park/Neutral Position Switch- Visually
inspect park/neutral position switch for indications of
physical damage and loose or corroded wire harness
connections. Refer toPark/Neutral Position
Switchin 21, Transmission.
²Starter Relay- Visually inspect starter relay
for indications of physical damage and loose or cor-
roded wire harness connections.
²Starter Motor- Visually inspect starter motor
for indications of physical damage and loose or cor-
roded wire harness connections.
²Starter Solenoid- Visually inspect starter sole-
noid for indications of physical damage and loose or
corroded wire harness connections.
²Wiring- Visually inspect wire harnesses for
damage or corrosion. Repair or replace any faulty
wiring, as required. Refer to 8, Wiring Diagrams.
TESTING
COLD CRANKING TEST
For complete starter wiring circuit diagrams, refer
to 8, Wiring Diagrams. The battery must be fully-
charged and load-tested before proceeding. Refer to
Batteryin 8, Battery.
(1) Connect volt-ampere tester to battery terminals
(Fig. 1). See instructions provided by manufacturer of
volt-ampere tester being used.
(2) Fully engage parking brake.
(3) Place gearshift selector lever in Park position.
(4) Verify that all lamps and accessories are
turned off.
(5) To prevent engine from starting, remove Fuel
Pump Relay. This relay is located in Power Distribu-
tion Center (PDC). Refer to label on PDC cover for
relay location.
WARNING: IF EQUIPPED WITH DIESEL ENGINE,
ATTEMPT TO START ENGINE A FEW TIMES
BEFORE PROCEEDING WITH FOLLOWING STEP.
Fig. 1 VOLTS-AMPS TESTER CONNECTIONS -
TYPICAL
1 - POSITIVE CLAMP
2 - NEGATIVE CLAMP
3 - INDUCTION AMMETER CLAMP
8F - 30 STARTING SYSTEMVA

(6) Rotate and hold ignition switch in Start posi-
tion. Note cranking voltage and current (amperage)
draw readings shown on volt-ampere tester.
(a) If voltage reads below 9.6 volts, refer to
Starter Motorin Diagnosis and Testing. If starter
motor is OK, refer toEngine Diagnosisin 9,
Engine for further testing of engine. If starter
motor is not OK, replace faulty starter motor.
(b) If voltage reads above 9.6 volts and current
(amperage) draw reads below specifications, refer
toFeed Circuit Testin this section.
(c) If voltage reads 12.5 volts or greater and
starter motor does not turn, refer toControl Cir-
cuit Testingin this section.
(d) If voltage reads 12.5 volts or greater and
starter motor turns very slowly, refer toFeed Cir-
cuit Testin this section.
NOTE: A cold engine will increase starter current
(amperage) draw reading, and reduce battery volt-
age reading.
FEED CIRCUIT TEST
The starter feed circuit test (voltage drop method)
will determine if there is excessive resistance in
high-amperage feed circuit. For complete starter wir-
ing circuit diagrams, refer 8, Wiring Diagrams.
When performing these tests, it is important to
remember that voltage drop is giving an indication of
resistance between two points at which voltmeter
probes are attached.
Example:When testing resistance of positive bat-
tery cable, touch voltmeter leads to positive battery
cable clamp and cable connector at starter solenoid.
If you probe positive battery terminal post and cable
connector at starter solenoid, you are reading com-
bined voltage drop in positive battery cable clamp-to-
terminal post connection and positive battery cable.
The following operation will require a voltmeter
accurate to 1/10 (0.10) volt. Before performing tests,
be certain that following procedures are accom-
plished:
²Battery is fully-charged and load-tested. Refer to
Batteryin 8, Battery.
²Fully engage parking brake.
²Place gearshift selector lever in Park position.
²Verify that all lamps and accessories are turned
off.
²To prevent engine from starting, remove Fuel
Pump Relay. This relay is located in Power Distribu-
tion Center (PDC). Refer to label on PDC cover for
relay location.
(1) Connect positive lead of voltmeter to negative
battery cable terminal post. Connect negative lead of
voltmeter to negative battery cable clamp (Fig. 2).
Rotate and hold ignition switch in Start position.
Observe voltmeter. If voltage is detected, correct poorcontact between cable clamp and terminal post.
(2) Connect positive lead of voltmeter to positive
battery terminal post. Connect negative lead of volt-
meter to battery positive cable clamp (Fig. 3). Rotate
and hold ignition switch in Start position. Observe
voltmeter. If voltage is detected, correct poor contact
between cable clamp and terminal post.
(3) Connect voltmeter to measure between battery
positive terminal post and starter solenoid battery
terminal stud (Fig. 4). Rotate and hold ignition
switch in Start position. Observe voltmeter. If read-
ing is above 0.2 volt, clean and tighten battery cable
connection at solenoid. Repeat test. If reading is still
above 0.2 volt, replace faulty positive battery cable.
Fig. 2 TEST NEGATIVE BATTERY CABLE
CONNECTION RESISTANCE - TYPICAL
1 - VOLTMETER
2 - BATTERY
Fig. 3 TEST POSITIVE BATTERY CABLE
CONNECTION RESISTANCE - TYPICAL
1 - VOLTMETER
2 - BATTERY
VASTARTING SYSTEM 8F - 31

(4) Connect voltmeter to measure between nega-
tive battery terminal post and a good clean ground
on engine block (Fig. 5). Rotate and hold ignition
switch in Start position. Observe voltmeter. If read-
ing is above 0.2 volt, clean and tighten negative bat-
tery cable attachment on engine block. Repeat test. If
reading is still above 0.2 volt, replace faulty negative
battery cable.(5) Connect positive lead of voltmeter to starter
housing. Connect negative lead of voltmeter to nega-
tive battery terminal post (Fig. 6). Rotate and hold
ignition switch in Start position. Observe voltmeter.
If reading is above 0.2 volt, correct poor starter to
engine block ground contact.
If resistance tests detect no feed circuit problems,
refer toStarter Motorin the Diagnosis and Testing.
CONTROL CIRCUIT TESTING
The starter control circuit components should be
tested in the order in which they are listed, as fol-
lows:
²Starter Relay- Refer toStarter RelayDiag-
nosis and Testing.
²Starter Solenoid- Refer toStarter Motor
Diagnosis and Testing.
²Ignition Switch- Refer toIgnition Switch
and Key Lock Cylinder
²Park/Neutral Position Switch- If equipped
with automatic transmission, refer toPark/Neutral
Position Switchin 21, Transmission.
²Wire harnesses and connections- Refer to 8,
Wiring Diagrams.
Fig. 4 TEST POSITIVE BATTERY CABLE
1 - BATTERY
2 - VOLTMETER
3 - STARTER MOTOR
Fig. 5 TEST GROUND CIRCUIT RESISTANCE -
TYPICAL
1 - VOLTMETER
2 - BATTERY
3 - ENGINE GROUND
Fig. 6 TEST STARTER GROUND - TYPICAL
1 - STARTER MOTOR
2 - BATTERY
3 - VOLTMETER
8F - 32 STARTING SYSTEMVA