Isuzu N-Series. Manual - part 753

Engine Control System (4JH1) 6E-63

P0100 (Symptom Code 9) (Flash Code 65)

Circuit Description
The mass air flow (MAF) sensor is an air flow meter
that measures the amount of air that enters the engine.
It is fitted between the air cleaner and turbocharger. A
small quantity of air that enters the engine indicates
deceleration or idle speed. A large quantity of air that
enters the engine indicates acceleration or a high load
condition. The MAF sensor has the following circuits.

• Ignition voltage circuit
• 5 volts reference circuit
• Low reference circuit
• MAF sensor signal circuit

The engine control module (ECM) provides 5 volts
reference voltage through the reference circuit to the
MAF sensor. The ECM monitors the voltage on the 5
volts reference circuit. If the ECM detects an
excessively low MAF sensor 5 volts reference voltage,
this DTC will set.

Condition for Running the DTC

• The ignition switch is ON.

Condition for Setting the DTC

• The ECM detects that the MAF sensor 5 volts

reference circuit voltage is less than 4.6 volts for
0.5 seconds.

Action Taken When the DTC Sets

• The ECM illuminates the malfunction indicator

lamp (MIL) when the diagnostic runs and fails.

• The ECM uses a MAF substitution of 1600 mg/strk

for engine control.

• The ECM uses an EGR solenoid valve control

substitution of 10%.

Condition for Clearing the MIL/DTC

• The ECM turns OFF the MIL when the diagnostic

runs and does not fail.

• A history DTC clears after 40 consecutive driving

cycles without a fault. Or clear with the Tech 2.

Diagnostic Aids

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

Notice:

• The MAF Sensor parameter on the Tech 2 will only

update with engine running.

Test Description
The number below refers to the step number on the
diagnostic table.
3. If the MAF sensor 5 volts reference circuit between
the ECM and the sensor is normal, the sensor signal
voltage low DTC P0100 (Symptom Code B) will set.

DTC P0100 (Symptom Code 9) (Flash Code 65)
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls
Connector End Views or Engine Control Module (ECM)
Connector End Views

Step

Action

Value(s)

Yes

Did you perform the Diagnostic System Check –
Engine Controls?

—

Go to Step 2

Go to Diagnostic

System Check –

Engine Controls

Install the Tech 2.

Turn OFF the ignition for 30 seconds.

Start the engine.

Monitor the Diagnostic Trouble Code (DTC)
Information with the Tech 2.

Does the DTC fail this ignition?

—

Go to Step 3

Go to Diagnostic

Aids

Turn OFF the ignition.

Disconnect the mass air flow (MAF) sensor
harness connector.

Start the engine and let idle for 30 seconds.

Monitor the DTC Information with the Tech 2.

Does DTC P0100 (Symptom Code B) set, but not
DTC P0100 (Symptom Code 9)?

—

Go to Step 5

Go to Step 4

6E-64 Engine Control System (4JH1)

Test the 5 volts reference circuit between the
engine control module (ECM) (pin 83 of B-233
connector) and the MAF sensor (pin 4 of J-
182 connector) for the following conditions:

• A short to ground
• A short to the low reference circuit

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 7

Go to Step 6

Replace the MAF sensor. Refer to Mass Air Flow
Sensor Replacement in this section.

Did you complete the replacement?

—

Go to Step 7

—

Important:
Replacement ECM must be programmed.

Replace the ECM. Refer to Engine Control Module
(ECM) Replacement in this section.

Did you complete the replacement?

—

Go to Step 7

—

Reconnect all previously disconnected
harness connector(s).

Clear the DTCs with the Tech 2.

Turn OFF the ignition for 30 seconds.

Start the engine.

Monitor the DTC Information with the Tech 2.

Did the DTC fail this ignition?

—

Go to Step 3

Go to Step 8

Observe the DTC Information with the Tech 2.

Are there any DTCs that you have not diagnosed?

—

Go to Diagnostic

Trouble Code (DTC)

List

System OK

Step

Action

Value(s)

Yes

Engine Control System (4JH1) 6E-65

P0100 (Symptom Code B) (Flash Code 65)

• Ignition voltage circuit
• 5 volts reference circuit
• Low reference circuit
• MAF sensor signal circuit

The engine control module (ECM) monitors the MAF
sensor signal for voltage outside the normal range of
the MAF sensor. If the ECM detects an excessively low
MAF sensor signal voltage, this DTC will set.

Condition for Running the DTC

• The ignition switch is ON.
• The engine is running.

Condition for Setting the DTC

• The ECM calculated MAF is lower than -18.6 kg/h

for 5 seconds. This indicates the ECM detects that
the MAF sensor signal voltage is smaller than a
predetermined range during engine run.

Action Taken When the DTC Sets

• The ECM illuminates the malfunction indicator

lamp (MIL) when the diagnostic runs and fails.

• The ECM uses a MAF substitution of 1600 mg/strk

for engine control.

• The ECM uses an EGR solenoid valve control

substitution of 10%.

Condition for Clearing the MIL/DTC

• The ECM turns OFF the MIL that the diagnostic

runs and does not fail.

• A history DTC clears after 40 consecutive driving

cycles without a fault. Or clear with the Tech 2.

Diagnostic Aids

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

Notice:

• Wrong direction of MAF sensor installation will

cause this DTC to set.

• Contaminated or restricted MAF sensor will cause

this DTC to set.

• The MAF Sensor parameter on the Tech 2 will only

update with engine running.

Test Description
The number below refers to the step number on the
diagnostic table.
5. If the MAF sensor signal circuit between the ECM
and the sensor is short to ground or any low reference
circuits, the sensor 5 volts reference voltage low DTC
P0100 (Symptom Code 9) will set.
6. If the MAF sensor signal circuit between the ECM
and the sensor is normal, the sensor signal voltage
high DTC P0100 (Symptom Code C) will set.

DTC P0100 (Symptom Code B) (Flash Code 65)
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls
Connector End Views or Engine Control Module (ECM)
Connector End Views

Step

Action

Value(s)

Yes

Did you perform the Diagnostic System Check –
Engine Controls?

—

Go to Step 2

Go to Diagnostic

System Check –

Engine Controls

Install the Tech 2.

Turn OFF the ignition for 30 seconds.

Start the engine and let idle for 30 seconds.

Monitor the Diagnostic Trouble Code (DTC)
Information with the Tech 2.

Does the DTC fail this ignition?

—

Go to Step 3

Go to Diagnostic

Aids

6E-66 Engine Control System (4JH1)

Turn OFF the ignition.

Disconnect the mass air flow (MAF) sensor
harness connector.

Connect a test lamp between the ignition
voltage feed circuit of the MAF sensor harness
(pin 2 of J-182 connector) and a known good
ground.

Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

—

Go to Step 4

Go to Step 7

Keep the ignition ON, with the engine OFF.

Connect a DMM between the 5 volts reference
circuit of the MAF sensor harness (pin 4 of J-
182 connector) and a known good ground.

Is the DMM voltage more than the specified value?

4.7 volts

Go to Step 5

Go to Step 8

Turn OFF the ignition.

Connect a 3-amp fused jumper wire between
the 5 volts reference circuit and the signal
circuit of the MAF sensor harness (pins 4 and
5 of J-182 connector).

Turn ON the ignition, with the engine OFF.
DO NOT start the engine.

Monitor the DTC Information with the Tech 2.

Does DTC P0100 (Symptom Code 9) set, but not
DTC P0100 (Symptom Code B)?

—

Go to Step 9

Go to Step 6

Keep the 3-amp fused jumper wire with
connected.

Start the engine and let idle for 30 seconds.

Does DTC P0100 (Symptom Code C) set, but not
DTC P0100 (Symptom Code B)?

—

Go to Step 11

Go to Step 10

Repair the open circuit or high resistance on the
ignition voltage feed circuit between the ECM main
relay (pin 5 of X-14 connector) and the MAF sensor
(pin 2 of J-182 connector).

Did you complete the repair?

—

Go to Step 15

—

Test the 5 volts reference circuit between the
engine control module (ECM) (pin 83 of B-233
connector) and the MAF sensor (pin 4 of J-
182 connector) for the following conditions:

• An open circuit
• A short to ground
• A short to the low reference circuit
• High resistance

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 15

Go to Step 12

Test the signal circuit between the ECM (pin
88 of B-233 connector) and the MAF sensor
(pin 5 of J-182 connector) for the following
conditions:

• A short to ground
• A short to the low reference circuit

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 15

Go to Step 14

Step

Action

Value(s)

Yes

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