Content .. 77 78 79 80 ..

Hummer H1 (2002+). Manual - part 79

___________________________________________

Transmission/Transfer Case 5-115

05745159

Replace the PCM. Refer to

PCM Replacement/Pro-

gramming

, Section 6.

Is the replacement complete?

—

Go to Step 17

—

Disconnect the internal wiring harness at the TCC
PWM Sol. Valve.

Measure the resistance of the TCC PWM Sol.
Valve.

Is the resistance within the specified values?

10-15

Go to Step 12

Go to Step 15

Measure the resistance between terminal E and ground
and terminal S and ground.
Are both readings greater than the specified value?

250

Go to Diag-

nostic Aids

Go to Step 13

Inspect the internal wiring harness for an open circuit.
Refer to Electrical Diagnosis, Section 8.
Did you find a problem?

—

Go to Step 16

—

Disconnect the internal wiring harness at the TCC
PWM Sol. Valve.

Measure the resistance between each of the com-
ponent terminals and ground.

Are both readings greater than the specified value?

250

Go to Step 14

Go to Step 15

Inspect the internal wiring harness for a short to
ground. Refer to Electrical Diagnosis, Section 8
Did you find a problem?

—

Go to Step 16

—

Replace the TCC PWM Sol. Valve. Refer to 4L80-E
On-Vehicle Service.
Is the replacement Complete?

—

Go to Step 17

—

Replace the Automatic Transmission Wiring Harness
Assembly (A/T Wiring Harness Assy). Refer to 4L80-E
On-Vehicle Service.
Is the replacement complete?

—

Go to Step 17

—

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

Select DTC.

Select Clear Info.

Operate the vehicle under the following conditions:

• The TCC PWM Sol. Valve is commanded ON

and the volts drop to zero.

• The TCC PWM Sol. Valve is commanded OFF

and the volts increase to B+.

• All conditions are met for 5 seconds.

Select Specific DTC. Enter DTC P1860.

Has the test run and passed?

—

System OK

Begin the

diagnosis

again. Go to

Step 1

DTC P1860 Torque Converter Clutch Pulse Width Modulation Solenoid Electrical (Cont’d)

Step

Action

Value

Yes

5-116

Transmission/Transfer Case

___________________________________________

DTC P1870 Transmission Component Slipping

Circuit Description

The PCM monitors the difference in engine speed and trans-
mission input speed. In D3 drive range with the converter
clutch engaged, engine speed should closely match transmis-
sion output speed. In D4 drive range with the converter clutch
engaged, clutch slip speed should be between -20 and +20 rpm.

This DTC detects excessive slip when the converter clutch is
engaged.

Conditions For Setting DTC

The following conditions are met for 10 seconds with 4th gear
commanded.

• No engine speed DTC P0335.

• No DTCs P0121, P0122, P0123, P0220,P0221, P0222,

P0223, P0225, P0226, P0227, P0228.

• No DTCs P0716 or P0717.

• No DTC P0722 or P0723.

• No DTCs P0741, P0742 or P0719.

• No shift solenoid 1-2 DTCs P0751 or P0753.

• No shift solenoid 2-3 DTCs P0756 or P0758.

• No DTC P1810.

• Gear range is D4.

• Throttle angle between 12% and 70%. Engine torque

between 60 and 280 ft/lbs.

• Fluid temperature is between -10°C and 130°C

(14° F and 266° F).

• Engine speed is between 1200 and 3750 rpm. Input

speed is between 40 and 205 rpm.

• Slip between +140 and +500 rpm is detected.

• Shift Solenoid performance counters are clear.

Action Taken When DTC Sets

• PCM will command maximum line pressure.

• PCM will inhibit converter clutch engagement.

• PCM inhibits 4th gear if in hot mode.

• PCM will freeze shift adapts. PCM illuminates 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

• A pressure switch malfunction could set DTC P1870.

• A mechanical failure of the shift solenoids, or converter

clutch solenoid could set a DTC P1870.

• Internal transmission failures may result in a DTC

P1870.

• If any engine DTCs or TPS codes are present diagnose

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.

1. This test checks the indicated range signal to the ac-

tual selected range. A faulty switch could set a DTC
P1870.

2. This test checks the torque converter for slippage

while in a commanded lock-up 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

Roller

Clutch

Rear

Band

Overdrive

1st

Off

2nd

Off

3rd

Off

4th

A = Applied

H = Holding

* = Holding but not effective

O = Overrunning

___________________________________________

Transmission/Transfer Case 5-117

05745159

DTC P1870 Transmission Component Slip

Step

Action

Value

Yes

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

—

Go to Step 2

Go to Power-

train OBD

System Check

Perform the Transmission Fluid Checking Procedure.
Refer to Line Pressure Check Procedure.
Did you perform the procedure?

—

Go to Step 3

Go to Trans-

mission Fluid

Checking Pro-

cedure

Install the scan tool (Tech 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 Freeze Frame and Failure
Records for reference. The Clear Info function will
erase the data.
3.

Record the DTC Freeze Frame and Failure
Records.

With the engine idling and at normal operating
temperature, apply the brake pedal.

Select each transmission range: D1, D2, D3, D4,
N, R and P.

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

—

Go to Step 4

Go to DTC

P1810 Pres-

sure Switch

Assembly

Malfunction

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

Perform the Line Pressure Check.

Refer to Line Pressure Check Procedure.

Is the line pressure within specifications?

—

Go to Step 5

Go to the

applicable

System Diag-

nosis Table:

Low Line

Pressure

High Line

Pressure

Drive the vehicle under the following conditions:

• The transmission is in D4.

• The TCC is engaged.

• The APP angle is 12-70%.

At any time is the TCC Slip Speed within the specified
range for 1 second?

140-500 RPM

Go to Step 6

Go to Diag-

nostic Aids

Drive the vehicle under the following conditions:

• The transmission is in D3.

• Command the TCC ON with the scan tool.

• The APP angle is 12-70%.

At any time is the TCC Slip Speed within the specified
range for 6 seconds?

140-500 RPM

Go to Step 8

Go to Step 7

5-118

Transmission/Transfer Case

___________________________________________

Repeat the procedure in step 5. Drive the vehicle under
the following conditions:

• The transmission is in D4.

• The TCC is engaged.

• The APP angle is 12-70%.

Are the results the same as in step 5?

140-500 RPM

Go to Step 9

Go to Step 11

Refer to 4L80-E System Diagnosis Table, Slipping
TCC.
Did you find and correct the problem?

—

Go to Step 12

—

Remove the transmission oil pan. Refer to Trans-
mission Oil Pan Removal in 4L80-E On-Vehicle
Service.

Inspect for contaminated fluid and excessive mate-
rial in the pan.

Is the fluid or the pan contaminated?

—

Go to 4L80-E

Unit Repair

Go to Step 10

Inspect the 1-2 SS Valve for contamination or dam-
aged seals.

Inspect the 2-3 SS Valve for contamination or dam-
aged seals.

Did you find a problem?

—

Go to Step 12

Go to Step 11

Inspect the following components for contamination or
sticking:

• The 1-2 shift valve.

• The 2-3 shift valve.

• The 3-4 shift valve.

Did you find a problem?

—

Go to Step 12

Go to 4L80-E

Unit Repair

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

Select DTC.

Select Clear Info.

Operate the vehicle under the following condi-
tions:

• Drive the vehicle in 4th gear, with the TCC com-

manded ON.

• The APP Angle is 12-70%.

• The PCM must see a slip of -25 to +30 RPM for

greater than 1 second.

Select Specific DTC. Enter DTC P1870.

Has the test run and passed?

—

System OK

Begin the

diagnosis

again. Go to

Step 1.

DTC P1870 Transmission Component Slip (Cont’d)

Step

Action

Value

Yes

Content .. 77 78 79 80 ..