Isuzu KB P190. Manual — part 308

6E-198 Engine Control System (4JH1)

Step Action

Value(s)

Yes

No

4

1. Check to ensure the brake pedal switch is

adjusted correctly. The plunger should be all the
way in when the pedal is released, yet should not
impede with the brake pedal full upward travel.

2. Adjust the brake pedal switch as necessary.
Did you find and correct the condition?



Go to Step 13

Go to Step 5

5

1. Turn OFF the ignition.
2. Disconnect the brake pedal switch harness

connector.

3. Turn ON the ignition, with the engine OFF.
4. Observe the Brake Pedal 1 Switch parameter

with the scan tool while momentarily jumping 3-
amp fused jumper wire across the brake pedal 1
switch harness connector between pins 1 and 2
of the C-44 connector.

Does the scan tool indicate Applied when the circuit
is jumpered and Released when the circuit is not
jumpered?



Go to Step 8

Go to Step 6

6

1. Test the brake pedal 1 switch signal circuit

between the ECM (pin 30 of C-56 connector) and
the brake pedal 1 switch (pin 2 of C-44
connector) for the following conditions:

• An open circuit
• A short to battery or ignition voltage
• High resistance

2. Repair the circuit(s) as necessary.
Did you find and correct the condition?



Go to Step 13

Go to Step 7

7

1. Turn OFF the ignition.
2. Disconnect the ECM harness connector.
3. Inspect for an intermittent and for a poor

connection on the brake switch circuit at the
harness connector of the ECM (pin 30 of C-56
connector).

4. Repair the connection(s) as necessary.
Did you find and correct the condition?



Go to Step 13

Go to Step 12

8

Replace the brake pedal switch. Refer to Brake
Pedal Switch Replacement in this section.
Did you complete the replacement?



Go to Step 13



9

1. Turn ON the ignition, with the engine OFF.
2. Fully depress and release the accelerator pedal

many times while observing the Accelerator
Pedal Position (APP) parameter with the scan
tool.

Is the APP parameter smoothly changed within 0 to
100 % when the accelerator pedal is depressed and
released?



Go to Diagnostic

Aids

Go to Step 10

10

1. Turn OFF the ignition.
2. Inspect for the following conditions:

• APP sensor is misadjusted.
• An accelerator pedal that is stuck

depressed.

• An intake throttle valve control cable that is

damaged, stuck or no free play.

• An intake throttle valve that is stuck open.

3. Repair or replace as necessary.
Did you find and correct the condition?



Go to Step 13

Go to Step 11

Engine Control System (4JH1) 6E-199

Step Action

Value(s)

Yes

No

11

Replace the accelerator pedal position sensor. Refer
to Accelerator Pedal Position Sensor Replacement
in this section.
Did you complete the replacement?



Go to Step 13



12

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 13



13

1. Reconnect all previously disconnected harness

connector(s).

2. Clear the DTCs with the scan tool.
3. Turn OFF the ignition for 30 seconds.
4. Turn ON the ignition, with the engine OFF.
5. Observe the APP parameter while fully

depressing and releasing the accelerator pedal
many times. Also observe the Brake Pedal 1
Switch parameter with the scan tool while
depressing and releasing the brake pedal.

Does the scan tool indicate the APP parameter
smoothly changed within 0 to 100 % when the
accelerator pedal is depressed and released, then
scan tool indicate the Brake Pedal 1 Switch
parameter Applied when the brake pedal is
depressed and Released when the brake pedal is
released?



Go to Step 14

Go to Step 2

14

Observe the DTC Information with the scan tool.
Are there any DTCs that you have not diagnosed?



Go to Diagnostic

Trouble Code (DTC)

List System

OK

6E-200 Engine Control System (4JH1)

DTC P1120 (Symptom Code E) (Flash Code 21)

Circuit Description
The accelerator pedal position (APP) sensor is mounted
on the intake throttle assembly. The engine control
module (ECM) uses the APP sensors to determine the
amount of acceleration or deceleration desired by the
person driving the vehicle via the fuel injection control.
The APP sensor has the following circuits.

• 5 volts reference circuit
• Low reference circuit
• APP sensor signal circuit

The ECM supplies 5 volts to the APP sensor on the 5
volts reference circuit. The ECM also provides a ground
on the low reference circuit. The APP sensor provides a
signal to the ECM on the APP sensor signal circuit,
which is relative to the position changes of the
accelerator pedal angle.
The idle switch is also mounted on the intake throttle
assembly. The idle switch is part of the APP sensor
assembly. The idle switch is a normally closed type
switch. When the accelerator pedal is released, the idle
switch signal to the ECM is low voltage.
If the ECM detects the APP sensor signal and the idle
switch out of correlation, this DTC will set.
Condition for Running the DTC

• The ignition switch is ON.

Condition for Setting the DTC
Either of following condition is met.

• The ECM detects APP sensor angle is less than

0.35%, then the idle switch is OFF for longer than
0.6 seconds.

• The ECM detects APP sensor angle is more than

8.7%, then the idle switch is ON for longer than 0.6
seconds.

Action Taken When the DTC Sets

• The ECM illuminates the malfunction indicator

lamp (MIL) when the diagnostic runs and fails.

• The ECM uses an engine speed substitution of

1400 RPM.

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 scan tool.

Diagnostic Aids

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

DTC P1120 (Symptom Code E) (Flash Code 21)
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. Turn ON the ignition, with the engine OFF.
2. Observe the Idle Switch parameter with the scan

tool while depressing and releasing the
accelerator pedal.

Does the scan tool indicate OFF when the
accelerator pedal is depressed and ON when the
accelerator pedal is released?



Go to Step 10

Go to Step 3

3

1. Turn OFF the ignition.
2. Disconnect the idle switch harness connector.
3. Turn ON the ignition, with the engine OFF.
4. Observe the Idle Switch parameter with the scan

tool while momentarily jumping 3-amp fused
jumper wire across the idle switch harness
connector between pins 1 and 2 of the E-23
connector.

Does the scan tool indicate ON when the circuit is
jumpered and OFF when the circuit is not jumpered?



Go to Step 9

Go to Step 4

Engine Control System (4JH1) 6E-201

Step Action

Value(s)

Yes

No

4

1. Turn ON the ignition, with the engine OFF.
2. Connect a DMM between the signal circuit of the

idle switch harness (pin 2 of E-23 connector) and
a known good ground.

Is the DMM voltage more than the specified value?

4.5 volts

Go to Step 5

Go to Step 6

5

Is the DMM voltage less than the specified value at
step 4?

5.5 volts

Go to Step 8

Go to Step 7

6

1. Test the switch signal circuit between the engine

control module (ECM) (pin 69 of C-56 connector)
and the idle switch (pin 2 of E-23 connector) for
the following conditions:

• An open circuit
• A short to ground
• High

resistance

2. Repair the circuit(s) as necessary.
Did you find and correct the condition?



Go to Step 21

Go to Step 18

7

Important: The idle switch may be damaged if the
switch signal circuit is shorted to a voltage source.
1. Test the switch signal circuit between the ECM

(pin 69 of C-56 connector) and the idle switch
(pin 2 of E-23 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 21

Go to Step 20

8

Repair the open circuit or high resistance on the idle
switch ground circuit between the idle switch (pin 1
of E-23 connector) and engine ground.
Did you complete the repair?



Go to Step 21



9

1. Turn OFF the ignition.
2. Inspect for an intermittent and for poor

connections at the harness connector of the idle
switch (pins 1 and 2 of E-23 connector).

3. Repair the connection(s) as necessary.
Did you find and correct the condition?



Go to Step 21

Go to Step 19

10

1. Turn ON the ignition, with the engine OFF.
2. Fully depress and release the accelerator pedal

many times while observing the Accelerator
Pedal Position (APP) parameter with the scan
tool.

Is the APP parameter smoothly changed within 0 to
100 % when the accelerator pedal is depressed and
released?



Go to Diagnostic

Aids

Go to Step 11

11

1. Turn OFF the ignition.
2. Reconnect the idle switch harness connector if

disconnected.

3. Disconnect the APP sensor harness connector.
4. Turn ON the ignition, with the engine OFF.
5. Connect a DMM between the 5 volts reference

circuit of the APP sensor harness (pin 3 of E-22
connector) and a known good ground.

Is the DMM voltage more than the specified value?

4.5 volts

Go to Step 12

Go to Step 13