2007 ISUZU KB P190 heater

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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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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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 6C1-2–212

• 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 pumping current control circuit DTC sets if the ECM detects the HO2S #1 signal voltage is outside the
predetermined range.
Conditions for Running the DTC
Condition 1
Run continuously once the following conditions are met:
• DTCs P0101, P0121, P0122, P0123, P0133, P0135, P0153, P0155, P0221, P0222, P0223, P0336 and P0338 ran
and passed.
• The ECM is commanding the lambda outside the range of 0.97 – 1.03.
• The engine is operating in closed loop.
• The HO2S heater is at operating temperature.
Condition 2
Run continuously once the following conditions are met:
• DTCs P0101, P0121, P0122, P0123, P0133, P0135, P0153, P0155, P0221, P0222, P0223, P0336 and P0338 ran
and passed.
• The ECM is commanding the lambda rich and then lean periodically with a change of greater than 2 percent.
• The ECM detects the internal HO2S signal voltage is 1.48 – 1.52 V.
• The HO2S is 0.97 – 1.03 lambda.
• The engine is operating in closed loop.
• The HO2S heater is at operating temperature.
Condition 3
Run continuously once the following conditions are met:
• DTCs P0133 and P0153 ran and passed.
• The HO2S heater is at operating temperature.
Conditions for Setting the DTC
Condition 1
The ECM detects the following conditions:
• The internal HO2S signal voltage change is 1.52 – 1.48 V.
• The above condition exists and 200 grams of exhausts gas has passed.
Condition 2
The ECM stores the fuel trim control values. This DTC sets if the ECM detects a deviation of greater than 10 percent
within 1.5 seconds between the stored value and the current value of the fuel trim.
Condition 3
The ECM detects that 5 seconds after decel fuel shut-off, the internal HO2S signal voltage is less than 1.7 V.

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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 6C1-2–215

10 1 Replace the appropriate HO2S. Refer to 6C1-3
Engine Management – V6 – Service Operations.
W as the repair completed? —
Go to Step 12 —
11 1 Replace the ECM. Refer to 6C1-3 Engine
Management – V6 – Service Operations.
W as 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. W hen the fuel system is lean, the
oxygen level will be high and the lambda signal will be high or more than 1. W hen 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.

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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 W iring 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 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

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Engine Management – V6 – Diagnostics Page 6C1-2–231

Engine Speed RPM 0 592
Coolant Temperature
°C 39 91
Intake Air Temperature
°C 32 26
Start Up ECT (Engine Coolant Temperature)
°C 39 34
Start Up IAT (Intake Air Temperature)
°C –48 30
Mass Air Flow Sensor
V 1.0 1.2
Engine Load % 100 22
Volumetric Efficiency % 99 15
Calculated Pedal Position % 0 0
Calculated Throttle Position % 5 1
Barometric Pressure kPa 102 102
Barometric Pressure V 4.88 4.88
Spark Advance
°CA 0 12
Ignition On Signal
Off / On On On
(1) Actual Gear -1- / -2- / -3- / -4- / -
5- / -P/N- / -R- / -Invalid- -P/N- -P/N-
DTC Set This Ignition
No DTC / DTC Set No DTC No DTC
Vehicle Speed km/h 0 0
Engine Runtime h:m:s 00:00:00 00:12:30
Ignition Accessory Signal Off / On On On
Mass Air Flow g/s 0.00 3.33
(1) Automatic Transmission Only (2) Manual Transmission Only
O2 Sensor Data
Tech 2 Display Units Displayed Ignition On Engine Running
Loop Status B1S1 (Bank 1 Sensor 1) Open / Closed Open Closed
Loop Status B2S1 (Bank 2 Sensor 1) Open / Closed Open Closed
Commanded B1S1 O2 Sensor Value (Bank 1 Sensor 1) :1 (= Lambda) 0.99 0.94
Commanded B2S1 O2 Sensor Value (Bank 2 Sensor 1) :1 (= Lambda) 0.99 0.94
B1S1 O2 Sensor (Bank 1 Sensor 1) :1 (= Lambda) 0.99 0.94
B1S2 O2 Sensor (Bank 1 Sensor 2) mV 438 538
B2S1 O2 Sensor (Bank 2 Sensor 1) :1 (= Lambda) 0.99 0.99
B2S2 O2 Sensor (Bank 2 Sensor 2) mV 438 486
B1S1 O2 Sensor Heater (Bank 1 Sensor 1) Ohm 540 80
B2S1 O2 Sensor Heater (Bank 2 Sensor 1) Ohm 540 80
Commanded B1S1 O2 Sensor Heater (Bank 1 Sensor 1) % 0.0 42.0
Commanded B2S1 O2 Sensor Heater (Bank 2 Sensor 1) % 0.0 42.0
B1 Short Term Fuel Trim (Bank 1) % 0 –1
B1 LTFT Idle/Deceleration (Bank 1 Long Term Fuel
Trim) % 0 1

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