Isuzu KB P190. Manual - part 456

ENGINE CONTROL SYSTEM (4JK1/4JJ1)   6E-207

6

1.

Remove the Meter (10A) fuse that supplies
voltage to the MIL.

2.

Turn ON the ignition, with the engine OFF.

3.

Measure the voltage from the MIL control
circuit in the ECM harness connector (pin 57
of C-58) to a known good ground.

Is the voltage less than the specified value?

1 volt

Go to Step 7

Go to Step 13

7

1.

Turn OFF the ignition.

2.

Reinstall the Meter (10A) fuse.

3.

Turn ON the ignition, with the engine OFF.

4.

Connect a 3-amp fused jumper wire between
the ECM harness connector (pin 57 of C-58)
and a known good ground.

Is the MIL illuminated?

—

Go to Step 11

Go to Step 8

8

1.

Turn OFF the ignition.

2.

Remove the IP cluster.

3.

Connect a test lamp between the ignition
voltage feed circuit of the IP cluster harness
connector (pin 8 of B-24) and a known good
ground.

4.

Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

—

Go to Step 9

Go to Step 14

9

1.

Test the control circuit between the ECM (pin
57 of C-58) and the IP cluster (pin 38 of B-23)
for an open circuit or high resistance.

2.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 17

Go to Step 10

10

1.

Inspect for an intermittent and for poor
connections at the harness connector of the
IP cluster (pin 8 of B-24 and pin 38 of B-23).

2.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 17

Go to Step 15

11

1.

Inspect for an intermittent and for a poor
connection at the harness connector of the
ECM (pin 57 of C-58).

2.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 17

Go to Step 16

12

Repair the short to ground between the ECM (pin
57 of C-58) and the IP cluster (pin 38 of B-23).

Did you complete the repair?

—

Go to Step 17

—

13

Repair the short to battery or ignition voltage
between the ECM (pin 57 of C-58) and the IP
cluster (pin 38 of B-23).

Did you complete the repair?

—

Go to Step 17

—

14

Repair the open circuit or high resistance on the
ignition voltage feed circuit between the Meter
(10A) fuse and the IP cluster (pin 8 of B-24).

Did you complete the repair?

—

Go to Step 17

—

15

Repair or replace the IP cluster.

Did you complete the repair or replacement?

—

Go to Step 17

—

Step

Action

Value(s)

Yes

No

6E-208   ENGINE CONTROL SYSTEM (4JK1/4JJ1)

16

Important: Replacement ECM must be
programmed and learned.
Replace the ECM. Refer to ECM Replacement.

Did you complete the replacement?

—

Go to Step 17

—

17

1.

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

2.

Clear the DTCs with a scan tool.

3.

Turn OFF the ignition for 30 seconds.

4.

Perform the MIL Control with a scan tool.

5.

Command the lamp ON and OFF.

Does the MIL turn ON and OFF with each
command?

—

Go to Step 18

Go to Step 3

18

Observe the DTC Information with a scan tool.

Are there any DTCs that you have not diagnosed?

—

Go to DTC List

System OK

Step

Action

Value(s)

Yes

No

ENGINE CONTROL SYSTEM (4JK1/4JJ1)   6E-209

DTC P0652 or P0653 (Flash Code 56)

Circuit Description

The ECM provides 5 volts reference voltage through
the reference circuit 2 to the following sensors:

• Accelerator pedal position (APP) sensor 2

• Fuel rail pressure (FRP) sensor

• Barometric pressure (BARO) sensor

• Camshaft position (CMP) sensor

• EGR position sensor

The 5 volts reference circuits are independent of each
other outside the ECM, but are bussed together inside
the ECM. Therefore, a short circuit condition on one 5
volts reference circuit affects the entire 5 volts
reference circuit 2. The ECM monitors the voltage on
the 5 volts reference circuit 2. If the ECM detects the
voltage is excessively low or high, DTC P0652 or
P0653 will set.

Condition for Running the DTC

• The battery voltage is more than 6 volts.

• The ignition switch is ON.

Condition for Setting the DTC

• The ECM detects that the 5 volts reference circuit

2 voltage is less than 4.7 volts. (DTC P0652)

• The ECM detects that the 5 volts reference circuit

2 voltage is more than 5.3 volts. (DTC P0653)

Action Taken When the DTC Sets

• The ECM illuminates the MIL when the diagnostic

runs and fails. Refer to DTC Type Definitions for
Action Taken When the DTC Sets - Type A.

• The ECM limits fuel injection quantity.

• The ECM inhibits pilot injection.

• The ECM inhibits EGR control.

• The ECM inhibits cruise control.

Condition for Clearing the DTC

• Refer to DTC Type Definitions for Condition for

Clearing the MIL/ DTC - Type A.

Diagnostic Aids

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

Notice:

• If this DTC is present, the engine cranks but does

not start.

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Controls
Connector End Views or ECM Connector End Views

Circuit/ System Testing DTC P0652

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 a scan tool.

2.

Turn OFF the ignition for 30 seconds.

3.

Start the engine.

4.

Monitor the DTC Information with a scan tool.

Does the DTC fail this ignition?

—

Go to Step 3

Go to Diagnostic 

Aids

3

1.

Turn OFF the ignition.

2.

Disconnect the barometric pressure (BARO)
sensor harness connector.

3.

Connect a DMM between the 5 volts reference
circuit (pin 3 of E-40) and a known good
ground.

4.

Turn ON the ignition, with engine OFF.

Is the DMM voltage more than the specified value?

4.7 volts

Go to Step 9

Go to Step 4

6E-210   ENGINE CONTROL SYSTEM (4JK1/4JJ1)

4

1.

Leave the DMM connected to the BARO
sensor harness connector.

2.

Turn OFF the ignition.

3.

Disconnect the EGR valve harness connector.

4.

Turn ON the ignition, with the engine OFF.

Does the DMM voltage change to more than the
specified value?

4.7 volts

Go to Step 10

Go to Step 5

5

1.

Leave the DMM connected to the BARO
sensor harness connector.

2.

Turn OFF the ignition.

3.

Disconnect the fuel rail pressure (FRP) sensor
harness connector.

4.

Turn ON the ignition, with the engine OFF.

Does the DMM voltage change to more than the
specified value?

4.7 volts

Go to Step 11

Go to Step 6

6

1.

Leave the DMM connected to the BARO
sensor harness connector.

2.

Turn OFF the ignition.

3.

Disconnect the camshaft position (CMP)
sensor harness connector.

4.

Turn ON the ignition, with the engine OFF.

Does the DMM voltage change to more than the
specified value?

4.7 volts

Go to Step 12

Go to Step 7

7

1.

Leave the DMM connected to the BARO
sensor harness connector.

2.

Turn OFF the ignition.

3.

Disconnect the accelerator pedal position
(APP) sensor harness connector.

4.

Turn ON the ignition, with the engine OFF.

Does the DMM voltage change to more than the
specified value?

4.7 volts

Go to Step 13

Go to Step 8

8

1.

Test the 5 volts reference circuit between the
ECM and the following components for a short
to ground or short to the low reference circuit:

• ECM (pin 19 of E-90) and BARO sensor

(pin 3 of E-40)

• ECM (pin 31 of E-90) and EGR position

sensor (pin 1 of E-71)

• ECM (pin 47 of E-90) and FRP sensor

(pin 3 of E-48)

• ECM (pin 46 of E-90) and CMP sensor

(pin 3 of E-39)

• ECM (pin 9 of C-58) and APP sensor 2

(pin 8 of C-40)

2.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 15

Go to Step 14

9

Replace the BARO sensor. Refer to BARO Sensor
Replacement.

Did you complete the replacement?

—

Go to Step 15

—

10

Replace the EGR valve. Refer to EGR Valve
Replacement.

Did you complete the replacement?

—

Go to Step 15

—

Step

Action

Value(s)

Yes

No