Content .. 750 751 752 753 ..

Isuzu N-Series. Service manual - part 752

Engine Control System (4JH1) 6E-59

P1650

(B)

CAN Device
Hang-up

—

• The ECM detects

internal CAN
controller does not
react.

• Faulty ECM.

P1651

(A)

CAN
Malfunction

—

• The ECM detects

that the PCU does
not receive the
CAN messages
from the ECM.

• CAN high circuit is open

circuit, high resistance,
short to ground, short to
battery or ignition
voltage.

• CAN low circuit is open

circuit, high resistance,
short to ground, short to
battery or ignition
voltage.

• Electrical interference.
• Magnetic interference.
• Faulty PCU.
• Faulty ECM.

P1651

(B)

CAN
Malfunction

—

• The ECM does not

receive the CAN
messages from the
PCU.

• CAN high circuit is open

circuit, high resistance,
short to ground, short to
battery or ignition
voltage.

• CAN low circuit is open

circuit, high resistance,
short to ground, short to
battery or ignition
voltage.

• Electrical interference.
• Magnetic interference.
• Faulty PCU.
• Faulty ECM.

P1690

(4)

OFF

Malfunction
Indicator Lamp
(MIL) Control
Circuit Low
Voltage

• The ignition switch

is ON.

• The ECM detects a

low voltage
condition on the
MIL control circuit
for longer than 3
seconds when the
MIL is commanded
OFF.

• Meter (10A) fuse (F-16)

open.

• MIL ignition voltage feed

circuit is open circuit or
high resistance.

• MIL control circuit is

open circuit, high
resistance or short to
ground.

• Poor harness connector

connection.

• MIL bulb burned out.
• Faulty instrument panel

cluster (meter
assembly).

• Faulty ECM.

DTC

(Symptom

Code)

Flash
Code

MIL

Status

DTC Name on

Tech 2

Condition for Running

the DTC

Condition for Setting

the DTC

Possible Cause

6E-60 Engine Control System (4JH1)

P1690

(8)

OFF

Malfunction
Indicator Lamp
(MIL) Circuit
High Voltage

• The ignition switch

is ON.

• The ECM detects a

high voltage
condition on the
MIL control circuit
for longer than 1
second when the
MIL is commanded
ON.

• MIL control circuit is

short to battery or
ignition voltage circuit.

• Faulty instrument panel

cluster (meter
assembly).

• Faulty ECM.

DTC

(Symptom

Code)

Flash
Code

MIL

Status

DTC Name on

Tech 2

Condition for Running

the DTC

Condition for Setting

the DTC

Possible Cause

Engine Control System (4JH1) 6E-61

P0100 (Symptom Code 7) (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 high 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 more than 5.2 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 7) (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 7)?

—

Go to Step 5

Go to Step 4

6E-62 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 battery or ignition voltage
• A short to the sensor ignition voltage

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

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