Hummer H1 (2006+). Manual — part 71

OBD-128

On-Board Diagnostics

_____________________________________________

DTC P0218 Transmission Fluid Over Temperature

Circuit Description

The flow of transmission fluid starts in the transmission pan. The fluid is then drawn through the filter and transmission case and
into the oil pump assembly. The oil pump pressurizes the fluid into main pressure that is regulated at the main pressure regulator
valve. From this point, fluid is directed to the torque converter clutch pulse width modulated (TCC PWM) solenoid and to the con-
trol main regulator and control main relief valve, into the control main filter assembly, and on to all solenoids for use as control
pressure. Hot fluid leaving the torque converter is routed through the converter flow valve to cooler lines and into the cooler assem-
bly. The transmission oil cooler is located in the radiator. The vehicle may be equipped with auxiliary oil cooler. The cooled fluid
is returned to the transmission through the return cooler line and to the transmission lube circuit. The automatic transmission fluid
temperature (TFT) sensor, which is part of pressure switch manifold (PSM) assembly, is located in the oil pan. If the transmission
control module (TCM) detects a high TFT for an extended period of time, then DTC P0218 sets.

DTC P0218 is a type C DTC.

Conditions for Setting the DTC

DTC P0218 sets when the TCM detects a transmission sump temperature greater than 126°C (252°F) for 10 seconds.

Action Taken When the DTC Sets

• The TCM does not illuminate the malfunction indicator lamp (MIL).

• The TCM freezes shift adapts from being updated.

• The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this informa-

tion as Failure Records.

• The TCM stores DTC P0218 in TCM history.

• The TCM inhibits TCC engagement.

Conditions for Clearing the DTC

• A scan tool can clear the code from TCM history. The TCM automatically clears the DTC from TCM history if the vehicle

completes 40 warm-up cycles without failure.

• The TCM cancels the DTC default actions when the condition no longer exists and the DTC passes the test.

Diagnostic Aids

• Verify the driving habits of the customer, such as trailer towing, etc.

• The scan tool TFT should rise steadily during warm-up cycles, then stabilize.

• DTC P0218 may set after DTC P0711 has set. Follow the diagnostic table for DTC P0711 before proceeding to the diagnos-

tic for DTC P0218.

• Repairing the condition that set DTC P0711 will likely eliminate DTC P0218.

Step

Action

Value(s)

Yes

No

1

NOTE: Before clearing DTC(s) use the scan tool “Capture info”
to record Freeze Frame and Failure Records for reference, as data
will be lost when “Clear Info” function is used

Was the “On-Board Diagnostic (OBD) System Check” per-
formed?

Go to step 2.

Go to OBD Sys-

tem Check.

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On-Board Diagnostics OBD-129

5745804

2

1.

Install the scan tool.

2.

Turn ON the ignition, with the engine OFF.

NOTE: Before clearing the DTC, use the scan tool in order to
record the Freeze Frame and Failure Records. The Clear Info
function will erase the data.

3.

Record the DTC Freeze Frame and Failure Records.

4.

Clear the DTC.

5.

Perform the Transmission Fluid Checking Procedure. Refer
to Transmission Fluid Checking Procedure .

Is the transmission fluid level correct?

Go to Step 3

Go to Transmis-

sion Fluid

Checking Proce-

dure

3

1.

Inspect the engine cooling system for the following condi-
tions:

• Air flow restrictions

• Air flow blockage

• System fluid level and condition

• Debris

2.

Inspect the transmission cooling system for the following
conditions:

• Air flow restrictions

• Air flow blockage

• System fluid level and conditions

• Debris

• Damaged cooler lines or hoses

Did you find and correct the condition?

Go to Step 6

Go to Step 4

4

Perform the Line Pressure Check Procedure.

Is the line pressure correct?

Go to Step 6

Go to Step 5

5

Inspect the torque converter stator for damage.

Did you find and correct the condition?

Go to Step 6

Go to Symp-

toms - Auto-

matic

Transmission

6

Perform the following procedure in order to verify the repair:

1.

Clear the DTC.

2.

Using the scan tool, monitor the TFT.

3.

Start the engine.

4.

The TFT must be less than 122°C (252°F) for at least 10 sec-
onds.

5.

Select Specific DTC.

6.

Enter DTC P0218.

Has the test run and passed?

System OK

Go to Step 1

Step

Action

Value(s)

Yes

No

OBD-130

On-Board Diagnostics

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DTC P0234 Turbo Charger Engine Overboost (Figure OBD-38)

Figure OBD-38: Turbocharger Boost Sensor Circuit

Circuit Description

The boost pressure sensor measures the pressure inside the intake manifold. Pressure in the intake manifold is affected by turbo-
charger output, engine speed, accelerator pedal input, air temperature, and barometric pressure (BARO). A diaphragm within the
boost pressure sensor is displaced by the pressure changes that occur from the varying load and operating conditions of the engine.
The sensor translates this action into electrical resistance. The boost pressure sensor wiring includes 3 circuits. The engine control
module (ECM) supplies a regulated 5 volts to the sensor on a 5-volt reference circuit. The ECM supplies a ground on a low refer-
ence circuit. The boost pressure sensor provides a signal voltage to the ECM, relative to pressure, on the boost pressure sensor sig-
nal circuit. The ECM converts the signal voltage input to a pressure value. Under normal operation the lowest pressure that can
exist in the intake manifold is equal to the BARO. This occurs when the vehicle is operated at idle or when the ignition is on while
the engine is off. Under these conditions, the ECM uses the boost pressure sensor to aid in diagnosis of the BARO sensor. The
highest manifold pressures occur when the turbocharger output is high. Manifold pressure can range from 58 kPa (8 psi) when
pressures are low to more than 240 kPa (34 psi) when pressures are high, depending on the BARO. The boost pressure sensor has a
range of 33 kPa (4 psi) to 255 kPa (36 psi). The ECM also uses the boost pressure sensor to provide engine overboost protection.
The ECM calculates a predicted value for the boost pressure sensor. The ECM then compares the predicted value to the sensor in-
put. If the ECM detects that the boost pressure sensor input is above the predicted range, this DTC will set.

Conditions for Setting the DTC

The measured boost pressure is above the expected range by 35 kPa or more for 12 seconds.

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On-Board Diagnostics OBD-131

5745804

Action Taken When the DTC Sets

• The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diag-

nostic 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 consecu-
tive 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 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.

Diagnostic Aids

• Any changes to the induction system or exhaust system, such as the installation of aftermarket parts, may cause this DTC to

set.

• If the condition is intermittent, refer to Intermittent Conditions.

Step

Action

Value(s)

Yes

No

1

NOTE: Before clearing DTC(s) use the scan tool “Capture info”
to record Freeze Frame and Failure Records for reference, as data
will be lost when “Clear Info” function is used

Was the “On-Board Diagnostic (OBD) System Check” per-
formed?

Go to step 2.

Go to OBD Sys-

tem Check.

2

If any of the following DTCs are set, go to that DTC first.

P0045

P0046

P2563

P2564

P2565

Are any of these DTCs set?

Go to the Diag-

nostic for each

Trouble Code in

numerical order

Go to Step 3

3

1.

Install a scan tool.

2.

Start the engine.

3.

Monitor the DTC Information with the scan tool.

Does the scan tool indicate that DTC P2229 is current?

Go to DTC

P2229

Go to Step 4

4

1.

Allow the engine to reach operating temperature.

2.

Turn OFF the ignition for 30 seconds.

3.

Turn ON the ignition, with the engine OFF.

Does the scan tool indicate that the difference between the boost
sensor pressure and the barometric pressure (BARO) sensor pres-
sure is more than the specified value?

10 kPa

Go to Step 5

Go to Step 7