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Isuzu KB P190. Manual - part 868

Engine Management – V6 – Diagnostics

Page 6C1-2–194

Using Tech 2, clear the DTCs.

Switch off the ignition for 30 seconds.

Start the engine.

Operate the vehicle within the conditions for
running the DTC.

Did DTC P2179 or P2189 fail this ignition cycle?

—

Go to Step 2

Go to Step 9

Using Tech 2, select the DTC display function.

Does Tech 2 display any DTCs?

—

Go to the

appropriate DTC

Table in this

Section System

7.54 DTC P2188 or P2190

DTC Descriptors

This diagnostic procedure supports the following DTCs:

•

DTC P2188 Fuel Trim System Rich at Idle Bank 1

•

DTC P2190 Fuel Trim System Rich at Idle Bank 2

Circuit Description

The engine control module (ECM) controls the air / fuel metering system to provide the best possible combination of
driveability, fuel economy, and emission control. Fuel delivery is controlled differently during Open and Closed Loop.
During Open Loop, the ECM determines fuel delivery based on sensor signals without heated oxygen sensor (HO2S)
input. During Closed Loop, the HO2S inputs are added and used by the ECM to calculate short and long term fuel trim
fuel delivery adjustments. If the HO2S indicate a lean condition, fuel trim values will be above 0 percent. If the O2S
indicate a rich condition, fuel trim values will be below 0 percent. Short term fuel trim values change rapidly in response
to the HO2S signals. Long term fuel trim makes coarse adjustments to maintain an air / fuel ratio of 14.7:1. If the ECM
detects an excessively rich condition, this DTC sets.

Conditions for Running the DTC

•

Before the ECM can report DTC P2188 or P2190 failed, DTCs P0101, P0121, P0122, P0123, P0133, P0153,
P0221, P0222, P0223, P0336, P0338, P0443, P0458, P0459, P0461, P0462, P0463, P2066, P2067, and P2068
must run and pass.

•

The fuel system is in Closed Loop.

•

The long fuel trim is active.

•

The engine coolant temperature (ECT) is more than 60°C (140°F).

•

The evaporative emission (EVAP) canister purge solenoid valve is not enabled.

•

The intake air temperature (IAT) is less than 60°C (140°F).

•

The fuel level is more than 11.6 percent.

•

The amount of air flow into the engine is more than 7 000 grams.

•

DTC P2188 and P2190 runs continuously once the above conditions are met for at least 300 seconds

Conditions for Setting the DTC

•

The Total Fuel Trim Avg. is less than –40 percent.

•

The LT FT Idle / Decel is less than -7 percent.

•

The condition exists for 4 seconds.

Engine Management – V6 – Diagnostics

Page 6C1-2–195

Action Taken When the DTC Sets

•

The control module activates 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 MIL/DTC

•

The control module 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

•

A fuel delivery condition causes this DTC to set. Thoroughly inspect all items that cause a rich condition.

•

For an intermittent fault condition, refer to 5.2

Intermittent Fault Conditions in this Section.

•

To assist diagnosis, refer to 3

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

diagram and connector charts.

Test Description

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

This step determines whether the fault is present.

If DTC P2188 and P2190 set at the same time, then both banks of the engine are operating rich. Inspect items that
would cause both banks to operate rich.

Disconnecting the mass air flow (MAF) sensor determines if the MAF sensor signal is skewed. If the Short Term
FT parameter changes more than the specified value, there is a condition with the MAF sensor. A MAF sensor
condition can cause this DTC without setting a MAF DTC. If there is a MAF sensor condition, the MAF sensor
parameters will appear to be within range.

DTC P2188 or P2190 Diagnostic Table

Step Action Value(s)

Yes

Has the Diagnostic System Check been completed?

—

Go to Step 2

Refer to

4.4 Diagnostic

System Check in

this Section

N O T E

If any DTCs are set, except P2188 and
P2190, refer to those DTCs before
proceeding with this diagnostic.

Idle the engine at the normal operating
temperature.

Check that the fuel system is in Closed Loop.

Observe the Total Fuel Trim Avg. parameter for
bank 1 and / or bank 2 with Tech 2.

Is the Total Fuel Trim Avg. less than the specified
value?

–40%

Go to Step 3

Go to Step 4

Engine Management – V6 – Diagnostics

Page 6C1-2–196

Observe the Freeze Frame and / or the Failure
Records data for this DTC.

Turn the ignition OFF for 30 seconds.

Start the engine.

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 and / or the Failure
Records data.

Does the DTC fail this ignition cycle?

—

Go to Step 4

Go to Additional

Information in this

DTC.

Are both banks of the engine operating rich?

—

Go to Step 5

Go to Step

Start the engine.

N O T E

Additional DTCs will set with the mass air
flow (MAF) sensor disconnected.

Disconnect the MAF sensor harness connector
while the engine is operating.

Observe the Short Term FT parameter for
Bank 1 and Bank 2 with Tech 2.

Connect the MAF sensor after completing this
step.

Does the Short Term FT parameter for both banks of
the engine change more than the specified value with
the MAF sensor disconnected?

20%

Go to 7.6

DTC

P0101, P0102 or

P0103

Go to Step 5

Inspect for the following conditions:

−

A collapsed air intake duct

−

A restricted air filter element

−

Inspect the MAF sensor for foreign
objects.

−

Excessive fuel in the crankcase – Change
the oil as necessary.

−

Contaminated fuel. Refer to 6.5 Alcohol /
Contaminants in Fuel Diagnosisin this
Section.

−

The engine control grounds for being
clean, tight, and in the correct locations

−

An engine mechanical condition – refer to
6A1 – Engine Mechanical V6.

Did you find and correct the condition?

—

Go to Step 8

Go to 6C Fuel

System – V6

Inspect for the following conditions:

−

Rich injectors – Refer to 6.2

Fuel

Injector Coil Test in this Section

−

Restricted exhaust system – Refer to 6F
Exhaust System – V6.

−

An engine mechanical condition – refer to
6A1 – Engine Mechanical V6.

Did you find and correct the condition?

—

Go to Step

Go to Additional

Information in this

DTC

Engine Management – V6 – Diagnostics

Page 6C1-2–197

Turn OFF the ignition for 30 seconds.

Using Tech 2, clear the DTCs and reset the fuel
trim system.

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.

Did DTC P2188 and / or P2190 fail this ignition cycle?

—

Go to Step 2

Go to Step 9

Using Tech 2, select the DTC display function.

Does Tech 2 display any DTCs?

—

Go to the

appropriate DTC

Table in this

Section System

7.55 DTC P2195 or P2197

DTC Descriptors

This diagnostic procedure supports the following DTCs:

•

DTC P2195 – B1S1 O2 Sensor – System Too Lean (Bank 1 Sensor 1)

•

DTC P2197 – B2S1 O2 Sensor – System Too Lean (Bank 2 Sensor 1)

Circuit Description

The wide band heated oxygen sensor 1 (HO2S1) measures the amount of oxygen in the exhaust system and provides
more information than the switching style HO2S2. 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, maintaining 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 P2195 or P2197 failed, DTCs P0137, P0138, P0140, P0141, P0157, P0158,
P0160, P0161, P2270, P2271, P2272, and P2273 must run and pass.

•

The front and rear heated oxygen sensors are at operating temperature.

•

The rear HO2S voltage signal is more than 850 mV.

•

The front HO2S is more than 1.08 lambda.

•

The Loop Status for both the front and rear sensors is Closed Loop.

•

DTCs P2195 and P2197 run continuously once the above conditions are met.

Conditions for Setting the DTC

Condition 1

•

The ECM detects that the front HO2S is operating too lean while the rear HO2S is operating too rich and the ECM
detects that the fuel trim is at maximum control,

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