Isuzu KB P190. Manual - part 871

Engine Management – V6 – Diagnostics

Page 6C1-2–206

•

The engine is running.

Conditions for Setting the DTC

DTC P2227

The ECM detects the BARO pressure changed greater than 5 kPa within 20 seconds or the BARO pressure changed
greater than 30 kPa since the last ignition cycle.

DTC P2228

The ECM detects the BARO sensor signal voltage is less than 0.20 V.

DTC P2229

The ECM detects the BARO sensor signal voltage is greater than 4.8 V for longer than 2.0 seconds.

Conditions for Clearing DTC

The BARO pressure sensor circuit DTCs are Type ‘B’ DTC. Refer to 1.4

Diagnostic Trouble Codes in this Section, for

action taken when a Type ‘B’ DTC sets and conditions for clearing Type ‘B’ DTCs.

Additional Information

•

Refer to 6C1-1 Engine Management – V6 – General Information for details of the BARO Sensor operation.

•

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.

Test Description

The following numbers refer to the step numbers in the diagnostic table:

Test signal circuit of the BARO sensor. This circuit should display a voltage within the specified range.

Measures the integrity of the TP sensor low reference circuit. Removal of the ECM Fuse 29 enables the ECM to
power down completely prior to the test procedure.

DTC P2227 P2228 or P2229 Diagnostic Table

Step Action

Yes

Has the Diagnostic System Check been performed?

Go to Step 2

Refer to

4.4 Diagnostic
System Check in

this Section

Switch off the ignition for 30 seconds.

Operate the vehicle within the conditions for running the DTC.

Using Tech 2, select the DTC display function.

Does DTC P2227, P2228 or P2229 fail this ignition cycle?

Go to Step 3

Refer to Additional

Information in this

DTC

Engine Management – V6 – Diagnostics

Page 6C1-2–207

Step Action

Yes

Switch off the ignition.

Disconnect the BARO sensor wiring connector.

Switch on the ignition with the engine not running.

Using a digital multimeter, measure the voltage between the
BARO sensor signal circuit and the ECM housing.

Does the multimeter display 4.5 – 5.5 V?

Go to Step 4

Go to Step 6

Switch on the ignition with the engine not running.

Using a digital multimeter, measure the voltage between the
BARO sensor 5 V reference circuit and the ECM housing.

Does the multimeter display 4.8 – 5.2 V?

Go to Step 5

Go to Step 7

Switch off the ignition.

Remove ECM / TCM Fuse 29 from the engine compartment
fuse and relay panel assembly.

Using a digital multimeter, measure the resistance between the
BARO sensor low reference circuit and the ECM housing.

N O T E

Install the ECM Fuse 29 to the engine compartment fuse
and relay panel assembly after completing this test.

Does the multimeter display 5

Ω?

Go to Step 9

Go to Step 8

Test BARO sensor signal circuit for a high resistance, open circuit,
short to ground or short to voltage fault condition. Refer to 8A
Electrical - Body and Chassis for information on electrical fault
diagnosis.

Was any fault found and rectified?

Go to Step 11

Go to Step 10

Test the BARO sensor 5 V reference circuit for an open, short to
ground or high resistance fault condition. Refer to 8A Electrical - Body
and Chassis for information on electrical fault diagnosis.

N O T E

The BARO sensor shares the 5 V reference circuit with
other sensors. A fault condition in the 5 V reference circuit
may trigger DTCs on sensors that share this circuit. Refer
to 3

Wiring Diagrams and Connector Charts in this

Section, to assist diagnosis.

Was any fault found and rectified?

Go to Step 11

Go to Step 10

Disconnect the ECM wiring connector.

Test the BARO sensor low reference circuit for a high resistance
and open circuit fault condition. Refer to 8A Electrical - Body
and Chassis for information on electrical fault diagnosis.

Was any fault found and rectified?

Go to Step 11

Go to Step 10

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

Was the repair completed?

Go to Step 11

—

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

Service Operations.

Was the repair completed?

Go to Step 11

—

Engine Management – V6 – Diagnostics

Page 6C1-2–208

Step Action

Yes

11 1

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.

Does any of the BARO pressure sensor circuit DTCs fail this ignition
cycle?

Go to Step 2

Go to Step 12

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, check the system for correct operation.

7.58 DTC P2231, P2232, P2234, P2235, P2251

or P2254

DTC Descriptors

This diagnostic procedure supports the following DTCs:

•

DTC P2231 – O2 Sensor Signal Interference by Heater Circuit (Bank 1, Sensor 1)

•

DTC P2232 – O2 Sensor Signal Short to Heater Circuit (Bank 1, Sensor 2)

•

DTC P2234 – O2 Sensor Signal Interference by Heater Circuit (Bank 2, Sensor 1)

•

DTC P2235 – O2 Sensor Signal Short to Heater Circuit (Bank 2, Sensor 2)

•

DTC P2251 – O2 Sensor Ground Circuit Malfunction (Bank 1, Sensor 1)

•

DTC P2254 – O2 Sensor Ground Circuit Malfunction (Bank 2, Sensor 1)

Circuit Description

The Engine control relay applies positive voltage to the heater ignition voltage circuits of the HO2S. The ECM applies a
pulse width modulated (PWM) ground to the heater control circuit of the HO2S through a device within the ECM called a
driver, to control the HO2S rate of heating.

O2 Sensor 1

The ECM maintains the voltage between the reference signal circuit and low reference circuit of the HO2S 1 to about
450 mV by increasing or decreasing the oxygen content in the HO2S diffusion gap. To achieve this, the ECM controls
the current applied to the oxygen pumping cell in the HO2S.

•

If the air / fuel mixture in the exhaust is balanced (lambda = 1), the oxygen pumping cell current is zero.

•

If the exhaust gas in the HO2S 1 diffusion gap is lean, the ECM applies a positive current to the oxygen pumping
cell to discharge oxygen from the diffusion gap.

•

If the exhaust gas in the HO2S 1 diffusion gap is rich, the ECM applies a negative current to the oxygen pumping
cell to draw oxygen into the diffusion gap.

The pumping current required to maintain the HO2S 1 signal circuit voltage to about 450 mV is proportional to the level
of oxygen concentration in the exhaust gas. The ECM monitors and evaluates the oxygen pumping current to determine
the level of oxygen concentration in the exhaust.

An HO2S signal circuit shorted to heater control circuit DTC sets if the ECM detects the HO2S signal voltage is
increasing or decreasing at the same rate as the HO2S heater control circuit.

O2 Sensor 2

The ECM applies a voltage of approximately 450 mV between the reference signal circuit and low reference circuit of the
HO2S 2 while the sensor temperature is less than the operating range.

Once the HO2S 2 reaches operating temperature, the sensor varies this reference signal voltage, which constantly
fluctuates between the high voltage output and the low voltage output.

Engine Management – V6 – Diagnostics

Page 6C1-2–209

The low voltage output is 0 – 450 mV, which occurs if the air fuel mixture is lean.

The high voltage output is 450 – 1,000 mV, which occurs if the air fuel mixture is rich.

The ECM monitors, stores and evaluates the HO2S 2 voltage fluctuation information to determine the level of oxygen
concentration in the exhaust.

Conditions for Running the DTC

DTC P2231 or P2234

Run continuously once the following conditions are met:

•

DTCs P0030, P0031, P0032, P0050, P0051, P0052, P0053, P0059, P0130, P0135, P0150 or P0155 are not set.

•

The HO2S heater control is enabled.

•

The HO2S heater duty cycle is greater than 5 percent.

•

The HO2S is at operating temperature for 10 seconds.

•

The ECM does not detect an engine misfire fault condition.

•

The fuel injectors are enabled.

•

The ignition voltage is 10.5 – 18 V.

•

The calculated exhaust temperature is less than 800

°C.

•

The MAF sensor signal output is steady within 3 percent of the airflow into the engine.

DTC P2232 and P2235

Run continuously once the following conditions are met:

•

The engine is running.

•

The HO2S is at operating temperature for longer than 90 seconds.

•

The fuel injectors are enabled.

•

The ignition voltage is greater than 10.5 V.

•

The calculated exhaust temperature is 250 – 800

°C.

DTC P2251 and P2254

Run continuously once the following conditions are met:

•

DTCs P0030, P0031, P0032, P0050, P0051 and P0052 ran and passed.

•

The HO2S heater control is enabled.

•

The ECM internal sensing element resistance is greater than 570

Ω.

•

The ECM detects the internal HO2S signal voltage is 1.47 – 1.53 V.

•

The HO2S is at operating temperature.

Conditions for Setting the DTC

DTC P2231 or P2234

The ECM detects the following conditions:

•

The internal HO2S signal voltage changes greater than 100 mV as the heater control switches.

•

The above condition occurs 18 times in the last 10 seconds.

DTC P2232 or P2235

The ECM detects the following conditions:

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