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Hummer H2. Manual - part 1532

Heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the
oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach
operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the
time required for the sensors to reach operating temperature. The powertrain control module (PCM) supplies the
HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started the PCM operates in
open loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperature and closed loop is
achieved, the HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias
voltage. High HO2S voltage indicates a rich exhaust stream; low HO2S voltage indicates a lean exhaust stream.
If the PCM detects an HO2S voltage that stays below a specified value, DTC P0131 sets for HO2S bank 1
sensor 1, or DTC P0151 sets for HO2S bank 2 sensor 1.

Conditions for Running the DTC

Lean Test Enable:

DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120,
P0200, P0220, P0300, P0442, P0446, P0452, P0453, P0455, P0496, P1125, P1258, P1516, P2101,
P2108, P2135, U0107 are not set.

The Loop Status parameter is closed.

The Ignition 1 Signal parameter is between 10-18 volts.

The Fuel Tank Level Remaining parameter is more than 10 percent.

The TP Indicated Angle parameter is between 3-70 percent more than the value observed at idle.

Power Enrichment Test Enable:

The Loop Status parameter is closed.

The Ignition 1 Signal parameter is between 10-18 volts.

The Fuel Tank Level Remaining parameter is more than 10 percent.

The Engine Run Time parameter is more than 30 seconds.

The Power Enrichment parameter is active for more than 1 second.

Conditions for Setting the DTC

Lean Test:

The PCM detects that the affected HO2S voltage parameter is less than 200 mV for 165 seconds.

Power Enrichment Test:

2004 Hummer H2

2004 ENGINE PERFORMANCE Engine Controls Diagnosis (DTC P0068 To DTC P0141/P0161) - 4.8L, 5.3L, and 6.0L -

Hummer H2

The PCM detects that the affected HO2S voltage parameter is less than 360 mV for 10 seconds.

Action Taken When the DTC Sets

The control module 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.

The control module commands the Loop Status open.

Conditions for Clearing the MIL/DTC

The control module turns OFF the malfunction indicator lamp (MIL) after 3 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.

Clear the MIL and the DTC with a scan tool.

Test Description

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

2: If the voltage is varying above and below the specified range, the condition is not present.

DTC P0131 or P0151

Step

Action

Value

(s)

Yes

Schematic Reference:Engine Controls Schematics
Connector End View Reference:Engine Controls Connector End Views or Powertrain Control
Module (PCM) Connector End Views

Did you perform the Diagnostic System Check-Engine
Controls?

Go to Step 2

Go to Diagnostic

System Check -

Engine Controls

1. Start the engine.

2. Allow the engine to reach operating

temperature. Refer to Scan Tool Data List .

3. Observe the affected HO2S voltage parameter

with a scan tool.

Is the HO2S voltage parameter varying above and

300-

600
mV

2004 Hummer H2

2004 ENGINE PERFORMANCE Engine Controls Diagnosis (DTC P0068 To DTC P0141/P0161) - 4.8L, 5.3L, and 6.0L -

Hummer H2

below the specified range?

Go to Step 3

Go to Step 4

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.

Did the DTC fail this ignition?

Go to Step 4

Go to

Intermittent

Conditions

1. Turn OFF the ignition.

2. Disconnect the affected heated oxygen sensor

(HO2S).

3. Turn ON the ignition, with the engine OFF.

4. Observe the HO2S voltage parameter with a

scan tool.

Is the HO2S voltage parameter less than the specified
value?

100
mV

Go to Step 6

Go to Step 5

1. Connect a 3-amp fused jumper wire between the

high signal circuit of the HO2S harness
connector on the engine harness side and a good
ground.

2. Observe the HO2S voltage parameter with a

scan tool.

Is the HO2S voltage parameter less than the specified
value?

100
mV

Go to Step 7

Go to Step 8

Test the HO2S high signal circuit for a short to
ground. Refer to Circuit Testing and Wiring Repairs
in Wiring Systems.
Did you find and correct the condition?

Go to Step 15

Go to Step 9

Test the HO2S low signal circuit for a short to the
HO2S heater low control circuit. Refer to Circuit
Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?

Go to Step 15

Go to Step 10

Test the HO2S high signal circuit for an open or high
resistance. Refer to Circuit Testing and Wiring
Repairs in Wiring Systems.
Did you find and correct the condition?

Go to Step 15

Go to Step 12

Test the HO2S high signal circuit for a short to the
following circuits:

2004 Hummer H2

2004 ENGINE PERFORMANCE Engine Controls Diagnosis (DTC P0068 To DTC P0141/P0161) - 4.8L, 5.3L, and 6.0L -

Hummer H2

HO2S low signal circuit

HO2S heater low control circuit

Refer to Circuit Testing and Wiring Repairs in
Wiring Systems.
Did you find and correct the condition?

Go to Step 15

Go to Step 12

1. The HO2S may be detecting a lean exhaust

condition or may be contaminated. Inspect for
the following conditions:

A silicon contaminated HO2S

Any water intrusion into the HO2S
connector

An exhaust leak between the HO2S and
the engine

Any vacuum leaks

An incorrect fuel pressure-Refer to Fuel
System Diagnosis .

Any lean fuel injectors-Refer to Fuel
Injector Balance Test with Tech 2 .

An inaccurate mass air flow (MAF)
sensor-Refer to Scan Tool Data List .

2. Repair any of the above or similar engine

conditions as necessary.

Did you find and correct the condition?

NOTE:

Refer to Silicon Contamination of
Heated Oxygen Sensors Notice in
Cautions and Notices.

Go to Step 15

Go to Step 11

Test for shorted terminals and for poor connections at
the HO2S. Refer to Testing for Intermittent
Conditions and Poor Connections and Connector
Repairs in Wiring Systems.
Did you find and correct the condition?

Go to Step 15

Go to Step 13

Test for shorted terminals and for poor connections at
the powertrain control module (PCM). Refer to
Testing for Intermittent Conditions and Poor
Connections and Connector Repairs in Wiring
Systems.
Did you find and correct the condition?

Go to Step 15

Go to Step 14

2004 Hummer H2

2004 ENGINE PERFORMANCE Engine Controls Diagnosis (DTC P0068 To DTC P0141/P0161) - 4.8L, 5.3L, and 6.0L -

Hummer H2

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