NOTE: All engines use a fixed ignition timing sys-
tem. Basic ignition timing is not adjustable. All
spark advance is determined by the Powertrain
Control Module (PCM).

The distributorless ignition system used on these

engines is referred to as the Direct Ignition System
(DIS). The system’s three main components are the
coils, crankshaft position sensor, and camshaft posi-
tion sensor. If equipped with the coil on plug ignition
system it utilizes an ignition coil for every cylinder, it
is mounted directly over the each spark plug.

OPERATION - IGNITION SYSTEM

The crankshaft position sensor and camshaft posi-

tion sensor are hall effect devices. The camshaft posi-
tion sensor and crankshaft position sensor generate
pulses that are inputs to the PCM. The PCM deter-
mines engine position from these sensors. The PCM
calculates injector sequence and ignition timing from
crankshaft & camshaft position. For a description of
both sensors, refer to Camshaft Position Sensor and
Crankshaft Position Sensor.

IGNITION CONTROL

8I - 1

SPECIFICATIONS

TORQUE

DESCRIPTION

N·m

Ft. Lbs.

In. Lbs.

2.0/2.4L Target Magnet

Screw

2.4L Camshaft Sensor

Screw

12.9

115

2.0L Camshaft Sensor

Screw

2.7L Camshaft Sensor

Screw

105

2.0/2.4L Ignition coil bolts

11.9

105

2.7L Ignition coil bolts

6.2

2.4L Spark Plugs *(Torque

Critical)

17.6 ±2

13 ±2

2.7L Spark Plugs

17.6

Knock Sensor

Ignition Coil Capacitor Nut

8.8

106

* Tapered seat plugs. Imperative that torque is NOT EXCEEDED.

SPARK PLUG CABLE RESISTANCE

2.0/2.4L

CABLE

Maximum Resistance

1, 2, 3, & 4

10.8K ohms

SPARK PLUG

Engine

Spark Plug

Gap

Thread Size

2.0/2.4L

RE14MCC5

0.048 TO 0.053

14mm (1 in.) reach

Engine

Spark Plug

Gap

Thread Size

2.7L

RE10PMC5

0.048 TO 0.053

14mm (1 in.) reach

AUTO SHUT DOWN RELAY

DESCRIPTION

The relay is located in the Power Distribution Cen-

ter (PDC). For the location of the relay within the
PDC, refer to the PDC cover for location. Check elec-
trical terminals for corrosion and repair as necessary

OPERATION

The ASD sense circuit (SBEC vehicles) or the

engine switched battery (NGC vehicles) informs the

PCM when the ASD relay energizes. A 12 volt signal
at this input indicates to the PCM that the ASD has
been activated. This input is also used to power cer-
tain drivers on NGC vehicles.

When energized, the ASD relay on SBEC vehicles

supplies battery voltage to the fuel injectors, ignition
coils and the heating element in each oxygen sensor.

When energized, the ASD relay on NGC vehicles

provides power to operate the injectors, ignition coil,
generator field, O2 sensor heaters (both upstream
and downstream), evaporative purge solenoid, EGR

8I - 2

IGNITION CONTROL

IGNITION CONTROL (Continued)

solenoid

(if

equipped)

wastegate

solenoid

(if

equipped), and NVLD solenoid (if equipped).

For both SBEC and NGC vehicles, the ASD relay

also provides a sense circuit to the PCM for diagnos-
tic purposes. If the PCM does not receive 12 volts
from this input after grounding the control side of
the ASD relay, it sets a Diagnostic Trouble Code
(DTC). The PCM energizes the ASD any time there is
an engine speed that exceeds a predetermined value
(typically about 50 rpm). The ASD relay can also be
energized after the engine has been turned off to per-
form an O2 sensor heater test, if vehicle is equipped
with OBD II diagnostics.

As mentioned earlier, the PCM energizes the ASD

relay during an O2 sensor heater test. This test is
performed only after the engine has been shut off for
SBEC vehicles. On NGC vehicles it checks the O2
heater upon vehicle start. The PCM still operates
internally to perform several checks, including moni-
toring the O2 sensor heaters.

CAMSHAFT POSITION
SENSOR

DESCRIPTION

The camshaft position sensor for the 4 cylinder

engine is mounted on the end of the cylinder head
(Fig. 1) or the front of the cylinder head on 2.7L (Fig.
3).

OPERATION

The CMP sensor contains a hall effect device that

provide cylinder identification to the Powertrain Con-
trol Module (PCM). The sensor generates pulses as
groups of notches on the camshaft sprocket or cam-
shaft target magnet pass underneath it. The PCM
keeps track of crankshaft rotation and identifies each
cylinder by the pulses generated by the notches on
the camshaft sprocket.

When metal aligns with the sensor, voltage goes

low (less than 0.3 volts). When a notch aligns with
the sensor, voltage spikes high (5.0 volts). As a group
of notches pass under the sensor, the voltage
switches from low (metal) to high (notch) then back
to low. The number of notches determine the amount
of pulses. If available, an oscilloscope or DRBIII

PEP Module can display the square wave patterns of
each timing event.

REMOVAL

REMOVAL - 4 CYLINDER

The camshaft position sensor is mounted to the

rear of the cylinder head.

(1) Remove the negative battery cable.
(2) Disconnect the PCV hose and reposition.
(3) Disconnect electrical connectors from the cam-

shaft position sensor (Fig. 1).

(4) Remove camshaft position sensor mounting

screws. Remove sensor.

(5) Loosen screw attaching target magnet to rear

of camshaft and remove magnet (Fig. 2).

Fig. 1 CAM SENSOR/EGR VALVE/PCV VALVE

1 - Camshaft Position Sensor
2 - PCV Valve
3 - EGR Valve and Transducer (if equipped)

Fig. 2 Target Magnet Removal/Installation

1 - TARGET MAGNET
2 - MOUNTING BOLT
3 - REAR OF CYLINDER HEAD

IGNITION CONTROL

8I - 3

AUTO SHUT DOWN RELAY (Continued)

REMOVAL - 2.7L

The camshaft position sensor is mounted in the

front of the head.

(1) Disconnect electrical connector from sensor.
(2) Remove camshaft position sensor screw.
(3) Without pulling on the connector, pull the sen-

sor out of the chain case cover (Fig. 3).

INSTALLATION

INSTALLATION - 4 CYLINDER

The target magnet has locating dowels that fit into

machined locating holes in the end of the camshaft
(Fig. 4).

(1) Install target magnet in end of camshaft.

Tighten mounting screw to 3 N·m (30 in. lbs.) torque.
Over torqueing could cause cracks in magnet. If mag-
net cracks replace it.

(2) Install camshaft position sensor. Tighten sensor

mounting screws to 12.9 N·m (115 in. lbs.) torque.

(3) Carefully attach electrical connector to cam-

shaft position sensor. Installation at an angle may
damage the sensor pins.

(4) Connect the PCV Valve hose.
(5) Connect the negative battery cable.

INSTALLATION - 2.7L

The camshaft position sensor is mounted in the

front of the head.

(1) Install sensor in the chain case cover and push

sensor in until contact is made with the boss on the
head. While holding the sensor in this position,

install and tighten the retaining bolt to 12 N·m (105
in. lbs.) torque.

(2) Attach electrical connector to sensor.

IGNITION COIL

DESCRIPTION

The ignition coil assembly for the 4 cylinder

engines consists of 2 independent coils molded
together. The coil assembly for the 4 cylinder engines
is mounted on the cylinder head cover. Spark plug
cables route to each cylinder from the coil. The coil
assemblies for the 2.7L are mounted on the head
cover. It is a coil on plug assembly and each cylinder
has an ignition coil assembly.

OPERATION

The coil for the 4 cylinder engines fires two spark

plugs every power stroke. One plug is the cylinder
under compression, the other cylinder fires on the
exhaust stroke. The Powertrain Control Module
(PCM) determines which of the coils to charge and
fire at the correct time.

The Auto Shutdown (ASD) relay provides battery

voltage to the ignition coil. The PCM provides a
ground contact (circuit) for energizing the ignition
coil. When the PCM breaks the contact, the magnetic
energy in the coil transfers to the secondary causing
the spark. The PCM will de-energize the ASD relay if
it does not receive the crankshaft position sensor and
camshaft position sensor inputs. Refer to Auto Shut-
down (ASD) Relay—PCM Output, in this section for
relay operation.

Fig. 3 CAM SENSOR LOCATION 2.7L

Fig. 4 Target Magnet Installation

1 - LOCATING DOWELS
2 - LOCATING HOLES (2)

8I - 4

IGNITION CONTROL

CAMSHAFT POSITION SENSOR (Continued)

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