Isuzu Trooper (1998-2002 year). Manual - part 291

6E–77

ENGINE DRIVEABILITY AND EMISSIONS

Malfunction Indicator Lamp (MIL) “ON” Steady

D06RW00007

Circuit description

The malfunction indicator lamp (MIL) should always be
illuminated and steady with ignition “ON” and the engine
stopped. Ignition feed voltage is supplied directly to the
MIL indicator. The powertrain control module (PCM)
turns the MIL “ON” by grounding the MIL driver circuit.
The MIL should not remain “ON” with the engine running
and no DTC(s) set. A steady MIL with the engine running
and no DTC(s) suggests a short to ground in the MIL
driver circuit.

Diagnostic Aids

An intermittent may be caused by a poor connection,
rubbed-through wire insulation, or a wire broken inside
the insulation. Check for the following items:

Poor connection or damaged harness – Inspect the
PCM harness and connectors for improper mating,
broken locks, improperly formed or damaged
terminals, poor terminal-to-wire connection, and
damaged harness.

Test Description

Number(s) below refer to the step number(s) on the
Diagnostic Chart.
2. If the MIL does not remain “ON” when the PCM is

disconnected, the MIL driver wiring is not faulty.

3. If the MIL driver circuit is OK, the instrument panel

cluster is faulty.

6. This vehicle is equipped with a PCM which utilizes

an electrically erasable programmable read only
memory (EEPROM). When the PCM is replaced,
the new PCM must be programmed. Refer to

UBS

98 model year Immobilizer Workshop Manual.

6E–78

ENGINE DRIVEABILITY AND EMISSIONS

Malfunction Indicator Lamp (MIL) “ON” Steady

Step

Action

Value(s)

Yes

Was the “On-Board diagnostic (OBD) System Check”
performed?

—

Go to

Step 2

Go to

OBD

System

Check

1. Ignition “OFF,” disconnect PCM.
2. Ignition “ON,” observe the MIL (Service Engine

Soon lamp).

Is the MIL “ON?”

—

Go to

Step 3

Go to

Step 5

1. Ignition “OFF,” disconnect the instrument panel

cluster.

2. Check the MIL driver circuit between the PCM and

the instrument panel cluster for a short to ground.

3. If a problem is found, repair as necessary.

Was the MIL driver circuit shorted to ground?

—

Go to

OBD

System

Check

Go to

Step 4

Replace the instrument panel cluster.

Is the action complete?

—

Go to

OBD

System

Check

—

1. Ignition “OFF,” reconnect the PCM.
2. Using Tech 2, select “Output Miscellaneous Test”

and command the MIL “OFF.”

Did the MIL turn “OFF?”

—

Go to

OBD

System

Check

Go to

Step 6

Replace the PCM.

IMPORTANT: The replacement PCM must be
programmed. Refer to

UBS 98model year Immobilizer

Workshop Manual.

Is the action complete?

—

Go to

OBD

System

Check

—

6E–79

ENGINE DRIVEABILITY AND EMISSIONS

Engine Cranks But Will Not Run

D06RX00004

6E–80

ENGINE DRIVEABILITY AND EMISSIONS

Circuit Description

The electronic Ignition system uses a coil-at-plug method
of spark distribution. In this type of ignition system, the
powertrain control module (PCM) triggers the correct
driver inside the ignition coil, which then triggers the
correct ignition coil based on the 58X signal received from
the crankshaft position sensor (CKP). The spark plug
connected to the coil fires when the ICM opens the ground
circuit for the coil’s primary circuit.
During crank, the PCM monitors the CKP 58X signal. The
CKP signal is used to determine which cylinder will fire
first. After the CKP 58X signal has been processed by the
PCM, it will command all six injectors to allow a priming
shot of fuel for all the cylinders. After the priming, the
injectors are left “OFF” during the next six 58X reference
pulses from the CKP. This allows each cylinder a chance
to use the fuel from the priming shot. During this waiting
period, a camshaft position (CMP) signal pulse will have
been received by the PCM. The CMP signal allows the
PCM to operate the injectors sequentially based on
camshaft position. If the camshaft position signal is not
present at start-up, the PCM will begin sequential fuel
delivery with a 1-in-6 chance that fuel delivery is correct.
The engine will run without a CMP signal, but will set a
DTC code.

Diagnostic Aids

An intermittent problem may be caused by a poor
connection, rubbed-through wire insulation or a wire
broken inside the insulation. Check for the following
items:

Faulty engine coolant temperature sensor – Using
Tech 2, compare engine coolant temperature with
intake air temperature on a completely cool engine.
Engine coolant temperature should be within 10

C of

intake air temperature. If not, replace the ECT sensor.

Test Description

Number(s) below refer to the step number(s) on the
Diagnostic Chart.
5. An obvious cause of low fuel pressure would be an

empty fuel tank.

6. The engine will easily start and run if a few injectors

are disabled. It is not necessary to test all injectors
at this time since this step is only a test to verify that
all of the injectors have not been disabled by fuel
contamination.

7. A blinking test light verifies that the PCM is

monitoring the 58X crankshaft reference signal and
is capable of activating the injectors. If there is an
open or shorted driver circuit, DTCs 201-206 should
be set.

19.By using a spark tester, each ignition coil’s ability to

produce 25,000 volts is verified.

25.If there is an open or shorted driver circuit, DTCs

201-206 should be set. All six injector driver circuits
can be checked at one time without removing the
intake manifold if a 5-8840-2636-0 test light is
available. This is the alternative procedure:

With the ignition “OFF,” disconnect the gray
connector located at the rear of the air filter, attached
to a bracket on the purge canister.

Connect test light 5-8840-2636-0 to the connector.
Do any of the light constantly illuminate or fail to blink
when the engine is cranked? If so, repair the short or
open circuit, or replace the PCM if indicated.

This procedure only tests the driver circuit as far as the
test connection, so step 31 is added to test the circuit all
the way to the injector.

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