Hummer H1 (2002+). Manual — part 70

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Transmission/Transfer Case 5-79

®

05745159

DTC P0724 Brake Switch Circuit High Input

Step

Action

Value

Yes

No

1

1.

Install scan tool.

2.

Turn ignition switch “on.”

NOTE: Important:

Before clearing DTC(s), use the

scan tool to record “Failure Records” for reference, as
data will be lost when the “Clear Info” function is used.

3.

Record the DTC “Failure Records.”

4.

Select “Brake Switch” on the scan tool.

5.

Disconnect the brake switch connector from he
brake switch.

Did the brake switch status change from “Closed” to
“Open?”

—

Go to Step 2

Go to Step 3

2

Replace brake switch.

—

Go to Step 5

—

3

Check switch wires circuit for short to B+.
Was a problem found?

—

Go to Step 5

Go to Step 4

4

Replace the PCM.
Is the replacement complete?

—

Go to Step 5

—

5

1.

After the repair is complete, use the scan tool to
select DTC,” then “Clear Info” function.

2.

Select “Specific DTC” and enter DTC “P0724.”

3.

Ensure the following conditions are met:

• Select “Brake Switch” on scan tool, depress

brake pedal. Switch state should change as pedal
is depressed.

—

—

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5-80

Transmission/Transfer Case

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DTC P0730 Incorrect Gear Ratio

Circuit Description

The Powertrain Control Module (PCM) calculates a ratio based
on the Automatic Transmission Input Shaft Speed Sensor (A/T
ISS) and Vehicle Speed Sensor (VSS) readings. The PCM
compares the known transmission gear ratio to the calculated
ratio, for the selected gear range.

If the PCM detects an incorrect gear ratio, then DTC P0730
sets. DTC P0730 is a type D DTC.

Conditions for Setting the DTC

The following conditions are met for 7 seconds:

• No MAP DTCs P0106, P0107, P0108.

• No A/T ISS Sensor DTCs P0716 or P0717.

• No OSS Sensor DTCs P0722 or P0723.

• No TFP Valve Position Switch DTC P1810.

• The Vehicle Speed is greater than 11 km/h (7 mph).

• The APP Angle is greater than 25%.

• The TFT is greater then 20ºC (68ºF).

• System voltage is 9.0-16.0 volts.

• Ten seconds must have elasped since the last gear range

change.

• The engine speed is greater than 475 RPM for at least 7

seconds.

• The engine speed is less than 3750 RPM.

• The engine torque is 100-642 N•m (80-475 lb ft).

• The Gear Ratio is one of the following:

• -Greater than 2.52 or less than 2.42

-Greater than 2.12 or less than 2.04
-Greater than 1.50 or less than 1.45
-Greater than 1.02 or less than 0.98
-Greater than 0.77 or less than 0.73
-Greater than 2.52 or less than 2.42

Action Taken When the DTC Sets

• The PCM does not illuminate the Malfunction Indicator

Lamp (MIL).

• The PCM commands maximum line pressure.

• The PCM freezes shift adapts.

• DTC P0730 is stored in PCM memory.

Conditions for Clearing the DTC

• A scan tool can clear the DTC from the PCM history.

The PCM clears the DTC from the PCM history if the
vehicle completes 40 warm-up cycles without a failure
reported.

• The PCM cancels the DTC default actions when the

fault no longer exits and the ignition is OFF long
enough to power down the PCM.

Diagnostic Aids

• Sticking or contaminated shift valves may cause an un-

defined gear ratio.

• Refer to the Shift Solenoid Valve State and Gear Ratio

table.

• First diagnose and clear any engine DTCs that are

present. Then inspect for any transmission DTCs that
may have reset. If a DTC P0717 Input Speed Sensor
Circuit Low Input

and a DTC P0730 are both present,

diagnose DTC P0717 first.

• DTC P1870 detects an incorrect gear ratio in fourth gear

with TCC applied.

Test Description

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

3. This step tests the indicated range signal to the actual

selected range. A faulty TFP Valve Position Switch
could set DTC P0730.

4. This step tests for proper ratios in each commanded

gear state.

Range

Gear

1-2 Sol

2-3 Sol

Fourth

Clutch

Overrun

Clutch

O/D

Roller

Clutch

FWD

Clutch

Direct

Clutch

Front

Band

Interm.

Sprag

Clutch

Interm

Clutch

Lo

Roller

Clutch

Rear

Band

Overdrive

1st

On

Off

– – H

A

–

–

*

–

H

–

2nd

Off

Off

– – H

A

–

–

H

A

O

–

3rd

Off

On

– – H

A

A

–

O

A

O

–

4th

Off

On

A

– O

A

A

–

O

A

O

–

A=Applied
H=Holding
*=Holding but not effective
O=Overrunning

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Transmission/Transfer Case 5-81

®

05745159

DTC P0730 Incorrect Gear Ratio

Step

Action

Value

Yes

No

1

Was the Powertrain On-Board Diagnostic (OBD) Sys-
tem Check performed?

–

Go to Step 2

Go to Power-

train OBD

System Check

2

Perform the Transmission Fluid Checking Procedure.
Refer to Transmission Fluid Checking Procedure.
Is the Procedure complete?

–

Go to Step 3

Go to Trans-

mission Fluid

Checking Pro-

cedure

3

1.

Install the scan tool.

2.

With the engine OFF, turn the ignition switch to
the RUN position.
Important:

Before clearing the DTCs, use the

scan tool in order to record the Failure Records for
reference. Using the Clear Info function erases the
stored Failure Records from the PCM.

3.

Record the DTC Freeze Frame and Failure
Records, then clear the DTCs.

4.

Start the engine.

5.

Apply the parking brake, and select each transmis-
sion range: D1, D2, D3, D4, N, R, and P.

Does the scan tool TFP Switch A/B/C display match
each selected gear range? (Refer to the Range Signal
table).

–

Go to Step 4

Refer to DTC

P1810 TFP

Valve Postion

Switch CKT

Malfunction

in

this section

4

1.

Drive the vehicle in Reverse and D4.

2.

Hold the vehicle speed above 11 km/h (7mph) for
greater than 2 seconds in the specified gear range.

3.

Use the scan tool snapshot mode in order to record
the transmission gear ratio for each commanded
gear range: Reverse, 1st, 2nd, 3rd and 4th.

Are the gear ratios within the parameters for each spec-
ified gear range?

Rev–2.04-2.12
1st–2.52-2.42
2nd–1.45-1.50
3rd–0.98-1.02
4th–0.73-0.77

Refer to Diag-

nostic Aids

Go to Step 5

5

1.

Connect the J–21867 Pressure Gauge to the trans-
mission line pressure tap.

2.

Perform the Line Pressure Checking Procedure.
Refer to Line Pressure Check Procedure.

Is the line pressure within specifications for each
selected gear range?

–

Go to Step 6

Go to Step 8

6

1.

Remove the transmission oil pan.
Refer to Changing the Fluid and Filter, in On-Vehi-
cle Service.

2.

Inspect the oil pan and the fluid for contamination.

Did you find excessive contamination?

–

Go to

Transmission

Overhaul

Procedure, in

Unit Repair

Go to Step 7

7

Inspect the transmission for the following problems:

• Sticking shift valves

• Stuck apply pistions

Did you find the condition?

–

Go to Step 10

Go to

Transmission

Overhaul

Procedure, in

Unit Repair.

5-82

Transmission/Transfer Case

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®

8

Is the system line pressure low only in the specific gear
which indicated an incorrect gear ratio?

–

Go to Step 9

Go to System

Diagnosis

Table; Low

Line Pressure

9

Inspect for fluid pressure loss in the following areas:

• 1-2 SS Valve seal

• 2-3 SS Valve seal

• Valve body passages

• Valve body gaskets

• Band apply pistons and seals

• Clutch apply pistons and seals

Did you find the condition?

–

Go to Step 10

Go to

Transmission

Overhaul

Procedure,

in Unit Repair

10

In order to verify your repair, perform the following
procedure:
1.

Select DTC.

2.

Select Clear Info.

3.

Operate the vehicle under the following condi-
tions:

• Start the engine

• Drive the vehicle in Reverse, 1st, 2nd, 3rd and

4th gear

• The PCM must see a valid gear ratio versus the

commanded gear ratio for 7 seconds

4.

Select Specific DTC. Enter DTC P0730.

Has the test run and passed?

–

System OK

Begin the

diagnosis

again.

Go to Step 1

DTC P0730 Incorrect Gear Ratio (Cont’d)

Step

Action

Value

Yes

No