Hummer H1 Service Manual page 279

5-80 Transmission/Transfer Case
DTC P0730 Incorrect Gear Ratio
Range Gear 1-2 Sol
1st On
2nd Off
Overdrive
3rd Off
4th Off
A=Applied
H=Holding
*=Holding but not effective
O=Overrunning
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
Fourth Overrun
2-3 Sol
Clutch Clutch
Off – –
Off – –
On – –
On A –
_____________________________________________
O/D
FWD Direct
Roller
Clutch Clutch
Clutch
H A –
H A –
H A A
O A A
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.
Interm.
Front Interm
Sprag
Band Clutch
Clutch
– * –
– H A
– O A
– O A
®
Lo
Rear
Roller
Band
Clutch
H –
O –
O –
O –