Hummer H1 Service Manual page 304

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Condition 3:
• No DTCs P0121, P0122, P0123, P0220, P0221, P0222,
P0223, P0225, P0226, P0227 or P0228.
• No DTCs P0716 or P0717.
• No DTCs P0722 or P0723.
• No 1-2 shift solenoid DTCs P0751 or P0753.
• No 3-4 shift solenoid DTCs P0756 or P0758.
• Engine speed is less 3750 rpm.
• Vehicle speed is greater than 8 km/h (5 mph).
• Throttle angle is greater than 12%.
• Engine torque is between 80 ft/lbs and 450 ft.lb.
• Engine running for more than 5 seconds.
• PSA indicates P/N when ratio indicates less than1.58:1
for more than 10 seconds.
• PSA indicates reverse when ratio indicates D4, D3, D2,
D1 for more than 15 seconds.
• PSA indicates D4, D3, D2, D1 when ratio indicates re-
verse for greater than 15 seconds.
Action Taken When The DTC Sets
• The PCM will command maximum line pressure.
• PCM assumes D4 for PRNDL shift pattern.
• The PCM will freeze shift adapts.
• The PCM will illuminate the warning lamp.
Conditions For Clearing DTC
• For California vehicles, the PCM will turn the lamp off
after three consecutive ignition cycles without a failure
reported.
• The DTC can be cleared using the scan tool. The DTC
will be cleared when the vehicle has achieved 40 warm-
up cycles without a failure reported.
• The PCM will cancel the DTC default actions when the
fault no longer exists and the ignition is cycled "off"
long enough to power down the PCM.
Diagnostic Aids
• Refer to the accompanying chart for the normal range
signals and the illegal combinations.
• Inspect the wiring for poor electrical connections at the
PCM and at the transmission 20-way connector. Look
for possible bent, backed out, deformed or damaged ter-
minals. Check for weak terminal tension as well. Also
05745159
Transmission/Transfer Case
check for a chafed wire that could short to bare metal or
other wiring. Inspect for a broken wire inside the insula-
tion.
• When diagnosing for a possible intermittent short or
open condition, move or massage the wiring harness
while observing test equipment for a change.
• This DTC can be falsely set during a fluid fill procedure.
After refilling, cycle key down, start and run vehicle for
20 seconds. Key down and allow the PCM to power
down and then restart the vehicle.
• This DTC can be set falsely by low pump pressure or a
stuck pressure regulator.
• This DTC can be set by a slipping forward clutch as-
sembly. It may allow the PCM to see a 2.08:1 ratio (re-
verse) when the manual valve position is indicated as
D4.
• If any engine DTCs or TP Sensor codes are present di-
agnose and clear these DTCs first. Then check to see if
the transmission DTCs have reset.
Test Description
The numbers below refer to the step numbers on the diagnostic
chart.
2. This test checks the indicated range signal to the man-
ual valve actually selected.
3. This test checks for correct voltage from the PCM to
the transmission 20-way connector.
Range Signal
Park OFF
Rev ON
Neutral OFF
D4 OFF
D3 OFF
D2 OFF
D1 ON
Illegal ON
Illegal ON
Expected Readings
"ON" = 0 volts/ "OFF = B+
5-105
A B C
ON OFF
ON OFF
ON OFF
ON ON
OFF ON
OFF OFF
OFF OFF
OFF ON
ON ON