Isuzu N-Series. Manual - part 776

 Engine Control System (4JH1)    6E-155

19

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 20

—

20

1.

Reconnect all previously disconnected fuse or
harness connector(s).

2.

Clear the DTCs with the Tech 2.

3.

Turn ON the ignition, with the engine OFF.

4.

Observe the Brake Pedal 1 Switch and the
Brake Pedal 2 Switch with the Tech 2 while
fully depressing and releasing the brake
pedal.

Does the Tech 2 indicate Applied when the brake
pedal is applied and Released when the brake
pedal is released?

—

Go to Step 21

Go to Step 2

21

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

No

6E-156    Engine Control System (4JH1) 

P0704 (Symptom Code 6) (Flash Code 57)

Circuit Description
The clutch pedal switch is installed on the clutch pedal
bracket.  The clutch pedal switch is a normally closed
type switch.  When the clutch pedal is pressed, the
clutch pedal switch signal to the engine control module
(ECM) is stopped (low voltage).  If the ECM detects the
clutch pedal switch signal does not change during a
predetermined vehicle speed range, this DTC will set.
This DTC will only run once per ignition cycle within the
enabling condition.

Condition for Running the DTC

• The ignition switch is ON.

Condition for Setting the DTC

• The ECM detects that the clutch pedal switch

signal does not change during the vehicle speed
changes between 5 km/h (3 MPH) and 80 km/h (50
MPH).  This DTC will only run once per ignition
cycle within the enabling condition.

Action Taken When the DTC Sets

• The ECM illuminates the malfunction indicator

lamp (MIL) when the diagnostic runs and fails.

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.

• Misadjusted clutch pedal switch will cause this

DTC to set.

DTC P0704 (Symptom Code 6) (Flash Code 57)
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

No

1

Did you perform the Diagnostic System Check –
Engine Controls?

—

Go to Step 2

Go to Diagnostic 

System Check – 

Engine Controls

2

1.

Install the Tech 2.

2.

Turn ON the ignition, with the engine OFF.

3.

Observe the Clutch Pedal Switch parameter
with the Tech 2 while fully depressing and
releasing the clutch pedal.

Does the Tech 2 indicate Applied when the clutch
pedal is applied and Released when the clutch
pedal is released?

—

Go to Diagnostic 

Aids

Go to Step 3

3

1.

Check to ensure the clutch pedal switch is
adjusted correctly.  The plunger should be all
the way in when the pedal is released, yet
should not impede with the clutch pedal full
upward travel.

2.

Adjust the clutch pedal switch as necessary.

Did you find and correct the condition?

—

Go to Step 14

Go to Step 4

4

1.

Turn OFF the ignition.

2.

Disconnect the clutch pedal switch harness
connector.

3.

Turn ON the ignition, with the engine OFF.

4.

Observe the Clutch Pedal Switch parameter
with the Tech 2 while momentarily jumping
across the clutch pedal switch harness
connector between pins 1 and 2 of B-89
connector.

Does the Tech 2 indicate Applied when the circuit is
jumped and Released when the circuit is not
jumped?

—

Go to Step 10

Go to Step 5

 Engine Control System (4JH1)    6E-157

5

1.

Connect a test lamp between the ignition
voltage feed circuit of the clutch pedal switch
harness (pin 1 of B-89 connector) and a
known good ground.

2.

Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

—

Go to Step 6

Go to Step 7

6

1.

Connect a test lamp between the signal circuit
of the clutch pedal switch harness (pin 2 of B-
89 connector) and a known good ground.

2.

Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

—

Go to Step 8

Go to Step 9

7

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 clutch pedal
switch (pin 1 of B-89 connector).

Did you complete the repair?

—

Go to Step 14

—

8

1.

Test the clutch pedal switch signal circuit
between the engine control module (ECM)
(pin 31 of B-234 connector) and the clutch
pedal switch (pin 2 of B-89 connector) for a
short to battery or ignition voltage.

2.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 14

Go to Step 13

9

1.

Test the clutch pedal switch signal circuit
between the ECM (pin 31 of B-234 connector)
and the clutch pedal switch (pin 2 of B-89
connector) for an open circuit or high
resistance.

2.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 14

Go to Step 11

10

1.

Turn OFF the ignition.

2.

Inspect for an intermittent and for poor
connections at the harness connector of the
clutch pedal switch (pins 1 and 2 of B-89
connector).

3.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 14

Go to Step 12

11

1.

Turn OFF the ignition.

2.

Disconnect the ECM harness connector.

3.

Inspect for an intermittent and for a poor
connection on the clutch pedal switch circuit at
the harness connector of the ECM (pin 31 of
B-234 connector).

4.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 14

Go to Step 13

12

Replace the clutch pedal switch.  Refer to Clutch
Pedal Switch Replacement in this section.

Did you complete the replacement?

—

Go to Step 14

—

Step

Action

Value(s)

Yes

No

6E-158    Engine Control System (4JH1) 

13

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 14

—

14

1.

Reconnect all previously disconnected fuse or
harness connector(s).

2.

Clear the DTCs with the Tech 2.

3.

Turn ON the ignition, with the engine OFF.

4.

Observe the Clutch Pedal Switch parameter
with the Tech 2 while fully depressing and
releasing the clutch pedal.

Does the Tech 2 indicate Applied when the clutch
pedal is applied and Released when the clutch
pedal is released?

—

Go to Step 15

Go to Step 3

15

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

No