used. Secondary, high-tension spark plug cables are
also used. One half of the coil fires two spark plugs
simultaneously (one plug is the cylinder under com-
pression, and the other plug is the cylinder on the
exhaust stroke). Coil half number one fires cylinders
1 and 4. Coil half number two fires cylinders 2 and 3.
The PCM determines which of the coils to charge and
fire at the correct time.

IGNITION CONTROL

8I - 1

The Auto Shutdown (ASD) relay provides battery

voltage to the ignition coil. The PCM provides a
ground contact (circuit) for energizing the coil. When
the PCM breaks the contact, the energy in the coil
primary transfers to the secondary causing a spark.
The PCM will de-energize the ASD relay if it does
not receive inputs from either the crankshaft or cam-
shaft position sensors.

A distributor is not used with the 2.4L engine.

4.0L

The 4.0L 6-cylinder engine uses a one-piece coil

rail containing three independent coils. Although cyl-
inder firing order is the same as 4.0L engines of pre-
vious years, spark plug firing is not. The 3 coils dual-
fire the spark plugs on cylinders 1-6, 2-5 and/or 3-4.
When one cylinder is being fired (on compression
stroke), the spark to the opposite cylinder is being
wasted (on exhaust stroke). The one-piece coil bolts
directly to the cylinder head. Rubber boots seal the
secondary terminal ends of the coils to the top of all
6 spark plugs. One electrical connector (located at
the rear end of the coil rail) is used for all three coils.

Because of coil design, spark plug cables (second-

ary cables) are not used. A distributor is not used
with the 4.0L engine.

The ignition system is controlled by the Powertrain

Control Module (PCM).

SPECIFICATIONS

SPECIFICATIONS - IGNITION TIMING
Ignition timing is not adjustable on any
engine.

ENGINE FIRING ORDER - 2.4L 4-CYLINDER
1 - 3 - 4 - 2. Refer to (Fig. 1).

ENGINE FIRING ORDER - 4.0L 6-CYLINDER
ENGINE

Fig. 1 FIRING ORDER - 2.4L

FIRING ORDER - 4.0L

8I - 2

IGNITION CONTROL

IGNITION CONTROL (Continued)

IGNITION COIL RESISTANCE - 2.4L

Engine

Coil Manufacture

Primary Resistance at
21°C-27°C (70°F-80°F)

Secondary Resistance at
21°C-27°C (70°F-80°F)

2.4L

Toyodenso or Diamond

0.51 to 0.61 Ohms

11,500 to 13,500 Ohms

IGNITION COIL RESISTANCE - 4.0L ENGINE

PRIMARY RESISTANCE 21-27°C (70-80°F)

0.71 - 0.88 Ohms

SPARK PLUGS

ENGINE

PLUG TYPE

ELECTRODE GAP

2.4L 4-Cylinder

RE16MC (Champion #)

0.94 to 1.09 mm (0.037 to 0.042 in.)

4.0L 6-Cylinder

ZFR5N (NGK #)

0.77 mm - 0.90 mm (0.030 in. - 0.035 in.)

SPECIFICATIONS - SPARK PLUG CABLE
RESISTANCE

MINIMUM

MAXIMUM

250 Ohms Per Inch

1000 Ohms Per Inch

3000 Ohms Per Foot

10,000 Ohms Per Foot

IGNITION COIL - 2.4L

IGNITION CONTROL

8I - 3

IGNITION CONTROL (Continued)

SPECIFICATIONS - TORQUE - IGNITION SYSTEM

DESCRIPTION

N·m

Ft. Lbs.

In. Lbs.

Camshaft Position Sensor

Mounting Bolt – 4.0L

Camshaft Position Sensor

– 2.4L

106

Ignition Coil Rail Mounting

Bolts – 4.0L

250

Ignition Coil Mounting

Bolts – 2.4L

105

Oil Pump Drive Hold-down

Bolt – 4.0L

Oil Pump Drive Housing

Cover Screws

** Spark Plugs - 2.4L

4-Cylinder

Spark Plugs - 4.0L

6-cylinder

** Torque critical tapered

design. Do not exceed 15

ft. lbs. torque.

AUTO SHUT DOWN RELAY

DESCRIPTION - PCM OUTPUT

The 5–pin, 12–volt, Automatic Shutdown (ASD)

relay is located in the Power Distribution Center
(PDC). Refer to label on PDC cover for relay location.

OPERATION

OPERATION - ASD SENSE - PCM INPUT

A 12 volt signal at this input indicates to the PCM

that the ASD has been activated. The relay is used to
connect the oxygen sensor heater element, ignition
coil and fuel injectors to 12 volt + power supply.

This input is used only to sense that the ASD relay

is energized. If the Powertrain Control Module
(PCM) does not see 12 volts at this input when the
ASD should be activated, it will set a Diagnostic
Trouble Code (DTC).

OPERATION - PCM OUTPUT

The ASD relay supplies battery voltage (12+ volts)

to the fuel injectors and ignition coil(s). With certain
emissions packages it also supplies 12–volts to the
oxygen sensor heating elements.

The ground circuit for the coil within the ASD

relay is controlled by the Powertrain Control Module

(PCM). The PCM operates the ASD relay by switch-
ing its ground circuit on and off.

The ASD relay will be shut–down, meaning the

12–volt power supply to the ASD relay will be de-ac-
tivated by the PCM if:

• the ignition key is left in the ON position. This

is if the engine has not been running for approxi-
mately 1.8 seconds.

• there is a crankshaft position sensor signal to

the PCM that is lower than pre-determined values.

DIAGNOSIS AND TESTING - ASD AND FUEL
PUMP RELAYS

The following description of operation and

tests apply only to the Automatic Shutdown
(ASD) and fuel pump relays. The terminals on the
bottom of each relay are numbered. Two different
types of relays may be used, (Fig. 2) or (Fig. 3).

• Terminal number 30 is connected to battery volt-

age. For both the ASD and fuel pump relays, termi-
nal 30 is connected to battery voltage at all times.

• The PCM grounds the coil side of the relay

through terminal number 85.

• Terminal number 86 supplies voltage to the coil

side of the relay.

• When the PCM de-energizes the ASD and fuel

pump relays, terminal number 87A connects to termi-
nal 30. This is the Off position. In the off position,

8I - 4

IGNITION CONTROL

IGNITION CONTROL (Continued)

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