Isuzu KB P190. Service manual — part 873

Engine Management – V6 – Diagnostics

Page 6C1-2–214

3

Are DTCs relating to the reference circuit of the HO2S
also set?
(e.g. 7.10 DTC P0130, P0131, P0132, P0135, P0137,
P0138, P0140, P0141, P0150 P0151, P0152, P0155,
P0157, P0158, P0160, P0161, P2243, P2247, P2270,
P2271, P2272, P2273, P2297 or P2298)

—

Go to the

appropriate DTC

Table in this

Section

Go to Step 4

4

1

Disconnect the appropriate HO2S wiring
connector.

2

Ignition ON, engine OFF.

3

Using a digital multimeter, measure the voltage
between the input pump current circuit and a
good ground.

Is the voltage more than the specified value?

50 mV

Go to Step 8

Go to Step 5

5

1

Ignition ON, engine OFF.

2

Using a digital multimeter, measure the voltage
between the pump current circuit and a good
ground.

is the voltage display more than the specified value?

50 mV

Go to Step 8

Go to Step 6

6

1

Connect a 3 A fused jumper wire between the
HO2S reference signal circuit and the low
reference circuit.

2

Ignition ON, engine OFF.

3

Using a digital multimeter, measure the voltage
between the input pump current circuit and a
good ground.

Is the voltage reading within the specified range?

4.8 – 5.2 V

Go to Step 7

Go to Step 8

7

1

Connect a 3 A fused jumper wire between the
HO2S reference signal circuit and the low
reference circuit.

2

Ignition ON, engine OFF.

3

Using a digital multimeter, measure the voltage
between the pump current circuit and a good
ground.

Is the voltage reading within the specified range?

4.8 – 5.2 V

Go to Step 9

Go to Step 10

8

1

Test the input pump current and the pump
current circuit of the HO2S for a high resistance,
open circuit, short to ground, short to voltage or
shorted together fault condition. Refer to 8A
Electrical-Body and Chassis for information on
electrical fault diagnosis.

Was any fault found and rectified?

—

Go to Step 12

Go to Step 11

9

1

Test or inspect for the following conditions that
may cause the HO2S to detect an incorrect
air / fuel mixture:

•

Lean or rich fuel injector fuel delivery,

•

Contaminated fuel,

•

Low fuel line pressure,

•

Exhaust leak near the HO2S, and

•

Leak in the crankcase or vacuum line.

Was any fault found and rectified?

—

Go to Step 12

Go to Step 10

Engine Management – V6 – Diagnostics

Page 6C1-2–215

10

1

Replace the appropriate HO2S. Refer to 6C1-3
Engine Management – V6 – Service Operations.

Was the repair completed?

—

Go to Step 12

—

11

1

Replace the ECM. Refer to 6C1-3 Engine
Management – V6 – Service Operations.

Was the repair completed?

—

Go to Step 12

—

12

1

Using Tech 2, clear the DTCs.

2

Switch off the ignition for 30 seconds.

3

Start the engine.

4

Operate the vehicle within the conditions for
running the DTC.

Does any of the HO2S pumping current control circuit
DTCs fail this ignition cycle?

—

Go to Step 2

Go to Step 13

12

Using Tech 2, select the DTC display function.

Does Tech 2 display any DTCs?

—

Go to the

appropriate DTC

Table in this

Section System

OK

When all diagnosis and repairs are completed, clear all DTCs and verify correct operation

7.60 DTC P2626, P2627, P2628, P2629, P2630

or P2631

DTC Descriptors

•

DTC P2626 – O2 Sensor Pump Current Trim Circuit Malfunction (Bank 1, Sensor 1)

•

DTC P2627 – O2 Sensor Pump Current Trim Circuit Low Voltage (Bank 1, Sensor 1)

•

DTC P2628 – O2 Sensor Pump Current Trim Circuit High Voltage (Bank 1, Sensor 1)

•

DTC P2629 – O2 Sensor Pump Current Trim Circuit Malfunction (Bank 2, Sensor 1)

•

DTC P2630 – O2 Sensor Pump Current Trim Circuit Low Voltage (Bank 2, Sensor 1)

•

DTC P2631 – O2 Sensor Pump Current Trim Circuit High Voltage (Bank 2, Sensor 1)

Circuit Description

The wide band heated oxygen sensor (HO2S) measures the amount of oxygen in the exhaust system and provides
more information than the switching style HO2S. The wide band sensor consists of an oxygen sensing cell, an oxygen
pumping cell, and a heater. The exhaust gas sample passes through a diffusion gap between the sensing cell and the
pumping cell. The engine control module (ECM) supplies a voltage to the HO2S and uses this voltage as a reference to
the amount of oxygen in the exhaust system.

An electronic circuit within the ECM controls the pump current through the oxygen pumping cell in order to maintain a
constant voltage in the oxygen sensing cell. The ECM monitors the voltage variation in the sensing cell and attempts to
keep the voltage constant by increasing or decreasing the amount of current flow, or oxygen ion flow, to the pumping
cell. By measuring the amount of current required to maintain the voltage in the sensing cell, the ECM can determine
the concentration of oxygen in the exhaust.

The HO2S voltage is displayed as a lambda value. A lambda value of 1 is equal to a stoichiometric air fuel ratio of
14.7:1. Under normal operating conditions, the lambda value will remain around 1. When the fuel system is lean, the
oxygen level will be high and the lambda signal will be high or more than 1. When the fuel system is rich, the oxygen
level will be low, and the lambda signal will be low or less than 1. The ECM uses this information to maintain the correct
air / fuel ratio.

Conditions for Running the DTC

•

Before the ECM can report DTC P2626 or P2629 failed, DTCs P0101, P0121, P0122, P0123, P0221, P0222,
P0223, P0336, and P0338 must run and pass.

•

The engine is operating.

Engine Management – V6 – Diagnostics

Page 6C1-2–216

•

The ignition voltage is between 10.7 – 18.0 volts.

•

The fuel system is in fuel shut-off mode.

•

The calculated exhaust temperature is less than 750°C.

•

The heated oxygen sensors are at operating temperature.

•

DTC P2626 and P2629 runs continuously once the above conditions are met.

Conditions for Setting the DTC

•

The ECM internal HO2S voltage is more than 4.81 volts.

•

The condition exists for more than 4 seconds or 600 seconds if the fuel level is less than 12 percent.

Action Taken When the DTC Sets

•

The ECM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the
diagnostic runs and fails.

•

The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic
fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the
second consecutive ignition cycle, the control module records the operating conditions at the time of the failure.
The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the DTC

•

The ECM turns OFF the malfunction indicator lamp (MIL) after four consecutive ignition cycles that the diagnostic
runs and does not fail.

•

A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

•

A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission
related diagnostic.

•

Use Tech 2 to clear the MIL and the DTC.

Additional Information

•

Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a
component harness connector.

•

The lower connector of the ECM is connector A43-X1 and the upper connector of the ECM is connector A43-X2.
Refer to 3 Wiring Diagrams and Connector Charts.

•

The front wide band sensors do not toggle or switch like a switching HO2S. The front HO2S signals will be
relatively stable for an idling engine.

•

For an intermittent fault condition, refer to 5.2

Intermittent Fault Conditions in this Section.

•

Since fault condition in a wiring connector may trigger DTCs, always test the connectors related to this diagnostic
procedure for shorted terminals or poor wiring connection before replacing any component. Refer to 8A Electrical-
Body and Chassis for information on electrical fault diagnosis.

•

To assist diagnosis, refer to 3

Wiring Diagrams and Connector Charts in this Section for the system wiring

diagram and connector charts.

•

The following table illustrates the typical voltages for the HO2S circuits:

HO2S Voltages

Conditions:

•

Ignition ON, Engine OFF

•

HO2S Disconnected

HO2S Circuit

Voltage

Heater Control

4.6 – 5.0 V

Heater Supply Voltage

B+

Reference Voltage

2.6 – 3.1 V

Engine Management – V6 – Diagnostics

Page 6C1-2–217

Low Reference

2.2 – 2.7 V

Pump Current

Less than 0.5 A

Input Pump Current

Less than 0.5 A

Test Description

The numbers below refer to the step numbers on the diagnostic table.

2

This step determines if the condition exists. The HO2S lambda parameter should react immediately to the changes
in throttle position when performing this test.

5

This step determines if there is a condition with the pumping current circuit. Connecting a jumper wire between the
reference voltage and the low reference circuits causes the ECM to command the pumping current and the input
pumping current circuits.

DTC P2626, P2627, P2628, P2629, P2630 or P2631 Diagnostic Table

Step Action Value(s)

Yes

No

1

Has the Diagnostic System Check been completed?

—

Go to Step 2

Refer to

4.4 Diagnostic

System Check

2

1

Start engine and allow to reach operating
temperature.

2

Cycle the throttle from idle to wide open throttle
(WOT), 3 times within 5 seconds.

3

Use Tech 2 to observe the affected HO2S
lambda value

Does the affected HO2S lambda value react
immediately to the above action?

—

Go to Step 3

Go to Step 4

3

1

Observe the Freeze Frame / Failure Records for
this DTC.

2

Turn OFF the ignition for 30 seconds.

3

Start the engine.

4

Operate the vehicle within the Conditions for
Running the DTC. You may also operate the
vehicle within the conditions that you observed
from the Freeze Frame / Failure Records.

Does P2626 P2627, P2628, P2629, P2630 or P2631
fail this ignition?

—

Go to Step 4

Go to Additional

Information in this

DTC

4

Is DTC P0131, P0132, P0151 or P0152 also set?

—

Go to the

appropriate DTC

Table in this

Section

Go to Step 5

5

1 Ignition

OFF.

2

Disconnect the appropriate heated oxygen
sensor (HO2S).

3

Ignition ON, engine OFF.

4

Connect a 3-amp fused jumper wire between the
reference voltage circuit and the low reference
circuit of the HO2S.

5

Measure the voltage between the pump current
circuit and a good ground.

Is the voltage more than the specified value?

1.0 V

Go to Step 7

Go to Step 6