2007 ISUZU KB P190 display

Engine Management – V6 – Diagnostics Page 6C1-2–207

Step Action Yes
No
3 1 Switch off the ignition.
2 Disconnect the BARO sensor wiring connector.
3 Switch on the ignition with the engine not running.
4 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
4 1 Switch on the ignition with the engine not running.
2 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
5 1 Switch off the ignition.
2 Remove ECM / TCM Fuse 29 from the engine compartment fuse and relay panel assembly.
3 Using a digital multimeter, measure the resistance between the BARO sensor low reference circuit and the ECM housing.
NOTE
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
6 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.
W as any fault found and rectified? Go to Step 11 Go to Step 10
7 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.
NOTE
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 W iring Diagrams and Connector Charts in this
Section, to assist diagnosis.
W as any fault found and rectified? Go to Step 11 Go to Step 10
8 1 Disconnect the ECM wiring connector.
2 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.
W as any fault found and rectified? Go to Step 11 Go to Step 10
9 Replace the BARO sensor. Refer to 6C1-3 Engine Management – V6
– Service Operations.
W as the repair completed? Go to Step 11 —
10 Replace the ECM. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
W as the repair completed? Go to Step 11 —

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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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ISUZU KB P190 2007

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 6C1-2–214

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.
W as 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.
W as any fault found and rectified? —
Go to Step 12 Go to Step 10

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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 6C1-2–218

6 1 Test the pump current circuit of the HO2S for an
open. Refer to 8A Electrical-Body and Chassis.
Did you find and correct the condition? —
Go to Step 11 Go to Step 8
7 1 Test for an intermittent and for a poor connection
at the appropriate HO2S. Refer to 8A Electrical-
Body and Chassis.
Did you find and correct the condition? —
Go to Step 11 Go to Step 9
8 1 Test for an intermittent and for a poor connection
at the engine control module (ECM). Refer to 8A
Electrical-Body and Chassis.
Did you find and correct the condition? —
Go to Step 11 Go to Step 10
9 1 Replace the HO2S. Refer to 6C1-3 Engine
Management – V6 – Service Operations.
Did you complete the replacement? —
Go to Step 11 —
10 1 Replace the ECM. Refer to 6C1-3 Engine
Management –V6 – Service Operations for
details on replacing the ECM.
Did you complete the replacement? —
Go to Step 11 —
11 1 Use Tech 2 to clear the DTCs.
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.
Did the DTC fail this ignition? —
Go to Step 2 Go to Step 12
12 1 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
7.61 DTC U0001
DTC Descriptor
This diagnostic procedure supports DTC U0001 – No Communication with CAN-Bus (High Speed).
Circuit Description
The engine control module (ECM) communicates directly with the control modules connected to the GM LAN serial data
communication circuit through the GM LAN protocol.
However, the immobiliser control unit (ICU) communicates with the ECM using the keyword 2000 protocol. Since the GM
LAN and keyword 2000 protocols are not compatible, a powertrain interface module (PIM) is integrated into the serial
data system to serve as a gateway. This gateway allows communication between the two protocols. Refer to 6E1
Powertrain Interface Module – V6 for further information on the GM LAN serial data communication circuit.
DTC U0001 sets if the ECM detects a fault condition in the serial data communication circuit.
Conditions for Running the DTC
DTC U0001 runs continuously when the following conditions are met:
The ignition voltage is 10.0 – 16.0 V.
The vehicle power mode requires serial data communication.

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