2007 ISUZU KB P190 check engine

Engine Management – V6 – Diagnostics Page 6C1-2–198

• The rear fuel trim, long and short term, is more than a threshold.
• This DTC sets after the air flow coming into the engine accumulates to more than 200 grams and the above
conditions are met for more than 4 seconds.
Condition 2
• The ECM detects that the rear HO2S is operating too rich while the ECM is commanding a lean air / fuel mixture.
• This DTC sets after the air flow coming into the engine accumulates to more than 800 grams and the above
condition is met for more than 4 seconds.
Action Taken When the DTC Sets
• The ECM activates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the
diagnostic runs and fails.
• The ECM 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 HO2S fault condition may cause this DTC to set. Thoroughly inspect all items that could cause a lean condition.
• For an intermittent fault condition, refer to 5.2 Intermittent Fault Conditions in this Section.
• Since a 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 W iring 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.
2 This step determines if a condition exists.
5 This step is testing for a rear HO2S sensor circuit condition. A circuit condition sets this DTC.
8 This step is testing for an intermittent circuit condition. Thoroughly inspect the HO2S circuits for an intermittent circuit condition.
9 This step is testing for an intermittent circuit condition. Thoroughly inspect the HO2S circuits for an intermittent circuit condition.
DTC P2195 or P2197 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 in this Section

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ISUZU KB P190 2007

Engine Management – V6 – Diagnostics Page 6C1-2–203

DTC P2196 or P2198 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 in this Section
2 1 Allow the engine to reach operating temperature.
2 Operate the vehicle within the parameters specified in Conditions for Running the DTC.
3 Observe the diagnostic trouble code (DTC) information, using Tech 2.
Did DTC P2196 or DTC P2198 fail this ignition? —
Go to Step 4 Go to Step 3
3 1 Observe the Freeze Frame and / or the Failure
records data for this DTC.
2 Turn the ignition OFF 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 and / or the Failure
records data.
Does the DTC fail this ignition cycle? —
Go to Step 4 Refer to Additional
Information in this DTC.
4 Is DTC P0041, P0137, P0138, P0140, P0157, P0158,
or P0160 also set? —
Go to the
appropriate DTC Table in this Section Go to Step 5
5 1 Operate the engine above 1,200 RPM for
30 seconds.
2 Observe the appropriate rear HO2S voltage, using Tech 2.
Is the voltage less than the specified value? 1,050 mV
Go to Step 8 Go to Step 6
6 1 Ignition OFF.
2 Disconnect the appropriate rear heated oxygen sensor (HO2S).
3 Ignition ON, engine OFF.
4 Observe the appropriate rear HO2S voltage parameter with Tech 2.
Is the voltage within the specified range? 350 – 550 mV
Go to Step 12 Go to Step 7
7 1 Test the appropriate rear HO2S signal circuit for
a short to voltage. Refer to 8A Electrical - Body
and Chassis.
Did you find and correct the condition? —
Go to Step 19 Go to Step 14
8 1 Shake the related HO2S harnesses for the front
sensor between the HO2S harness connector
and the engine control module (ECM) while
monitoring the appropriate HO2S lambda
parameter.
Does the HO2S parameter change abruptly while
moving the related harnesses? —
Go to Step 15 Go to Step 9

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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 W iring 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:
4 Test signal circuit of the BARO sensor. This circuit should display a voltage within the specified range.
5 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 No
1 Has the Diagnostic System Check been performed?
Go to Step 2 Refer to
4.4 Diagnostic
System Check in this Section
2 1 Switch off the ignition for 30 seconds.
2 Operate the vehicle within the conditions for running the DTC.
3 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

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Engine Management – V6 – Diagnostics Page 6C1-2–208

Step Action Yes
No
11 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 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 (PW M) 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.

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Engine Management – V6 – Diagnostics Page 6C1-2–210

• The internal HO2S signal voltage switches at the same rate as the heater circuit.
• The above condition occurs 4 times out of 6 as the heater is turned off.
DTC P2251 or P2254
The ECM detects the following conditions:
• The internal HO2S signal voltage changes greater than 10 mV as the heater control switches.
• The above condition occurs 20 times in the last 10 seconds.
Conditions for Clearing the DTC
The HO2S signal circuit shorted to heater control circuit DTCs are Type ‘B’ DTCs. Refer to 1.4 Diagnostic Trouble
Codes in this Section, for action taken when 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 HO2S system operation.
• For an intermittent fault condition, refer to 5.2 Intermittent Fault Conditions in this Section.
• The HO2S must be tightened correctly. A loose HO2S will trigger these DTCs.
• 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 W iring Diagrams and Connector Charts in this Section, for the system wiring
diagram and connector charts.
DTC P2231, P2232, P2234, P2235, P2251or P2254 Diagnostic Table
Step Action Yes No
1 Has the Diagnostic System Check been performed?
Go to Step 2 Refer to
4.4 Diagnostic
System Check in this Section
2 1 Switch off the ignition for 30 seconds.
2 Start the engine.
3 Allow the engine to reach the normal operating temperature.
4 Increase the engine speed to 2,000 rpm for 10 seconds.
5 Using Tech 2, select the DTC display function.
Does DTC P2231, P2232, P2234, P2235, P2251 or P2254 fail this
ignition cycle? Go to Step 3 Refer to Additional
Information in this DTC
3 1 Disconnect the appropriate HO2S connector.
2 From the HO2S to the sensor wiring connector, test the following circuit for a shorted to the sensor heater control circuit
fault condition:
• Reference signal circuit,
• low reference circuit,
• pump current,
• input pump current.
Refer to 8A Electrical - Body and Chassis for information on electrical fault diagnosis.
W as any fault found? Go to Step 6 Go to Step 4

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ISUZU KB P190 2007

Engine Management – V6 – Diagnostics Page 6C1-2–211

Step Action Yes No
4 1 Disconnect the ECM and the appropriate HO2S connector.
2 From the HO2S wiring connector to the ECM wiring connector, test the following circuit for a shorted to the sensor heater
control circuit fault condition:
• Reference signal circuit,
• low reference circuit,
• pump current,
• input pump current.
Refer to 8A Electrical - Body and Chassis for information on electrical fault diagnosis.
W as any fault found and rectified? Go to Step 8 Go to Step 7
6 Replace the appropriate HO2S. Refer to 6C1-3 Engine Management
– V6 – Service Operations.
W as the repair completed? Go to Step 8 —
7 Replace the ECM. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
W as the repair completed? Go to Step 8 —
8 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 O2 Sensor Signal Circuit Shorted to Heater Control
Circuit DTCs fail this ignition cycle? Go to Step 2 Go to Step 9
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 OK
When all diagnosis and repairs are completed, check the system for correct operation.
7.59 DTC P2237, P2238, P2239, P2240, P2241
or P2242
DTC Descriptors
This diagnostic procedure supports the following DTCs:
• DTC P2237 – O2 Sensor Pump Current Circuit Malfunction (Bank 1, Sensor 1)
• DTC P2238 – O2 Sensor Pump Current Circuit Low Voltage (Bank 1, Sensor 1)
• DTC P2239 – O2 Sensor Pump Current Circuit High Voltage (Bank 1, Sensor 1)
• DTC P2240 – O2 Sensor Pump Current Circuit Malfunction (Bank 2, Sensor 1)
• DTC P2241 – O2 Sensor Pump Current Circuit Low Voltage (Bank 2, Sensor 1)
• DTC P2242 – O2 Sensor Pump Current Circuit High Voltage (Bank 2, Sensor 1)
Circuit Description
The engine control relay applies positive voltage to the heater ignition voltage circuits of the HO2S #1. The ECM applies
a pulse width modulated (PW M) 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.
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.

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Engine Management – V6 – Diagnostics Page 6C1-2–213

Conditions for Clearing the DTC
The HO2S pumping current control circuit DTCs are Type ‘B’ DTCs. Refer to 1.4 Diagnostic Trouble Codes in this
Section for action taken when 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 HO2S system operation.
• For an intermittent fault condition, refer to 5.2 Intermittent Fault Conditions in this Section.
• Inspect the HO2S wiring harness for contact with the exhaust system.
• The HO2S must be tightened correctly. A loose HO2S will trigger these DTCs.
• 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 W iring 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
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 following numbers refer to the step numbers in the diagnostic table:
2 W hen performing this test, the HO2S should react immediately.
4 Connecting a jumper wire between the HO2S reference signal circuit and the low reference circuit causes the ECM to apply signal voltage to the pumping current and input pumping current.
DTC P2237, P2238, P2239, P2240 or P2242 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 Switch off the ignition for 30 seconds.
2 Start the engine.
3 Allow the engine to reach the normal operating temperature.
4 Increase the engine speed to 2,000 rpm for 10 seconds.
5 Using Tech 2, select the DTC display function.
Does DTC P2237, P2238, P2239, P2240, P2241,
P2242, fail this ignition cycle? —
Go to Step 3 Refer to Additional
Information in this DTC

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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 (W OT), 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

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