GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1997 🢒 Safari - 2WD 🢒 Transmission/Transaxle 🢒 Automatic Transmission - 4L60-E 🢒 DTC P1870 Transmission Component Slipping
Table 1: DTC P1870 Transmission Slipping Component

Object Number: 42275 Size: MF
Automatic Transmission Components
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice

Range

Gear

Shift Solenoid

TCC Solenoid

TCC PWM Solenoid

2-4 Band

Forward Clutch

3-4 Clutch

Torque Converter Clutch

1-2

2-3

Overdrive

4th

ON

OFF

ON

90% (ON)

Applied

Applied

Applied

Applied

Circuit Description

The VCM monitors the difference between engine speed and transmission output speed. In D3 drive range with the TCC engaged, the engine speed should closely match the transmission output speed. In D4 drive range, with the TCC engaged, the TCC slip speed should be -20 to +20 RPM.

When the VCM detects excessive TCC slip when the TCC should be engaged, then DTC P1870 sets. DTC P1870 is a type B DTC.

Conditions for Setting the DTC

DTC P1870 sets if the following conditions are met for three TCC cycles with reported excessive TCC slip conditions, two consecutive times.

    • No TP DTCs P0122 or P0123
    • No VSS Assy. DTC P0502
    • No TFT Sensor DTCs P0712 or P0713
    • No TCC Sol. Valve DTC P0740
    • No 1-2 SS Valve DTCs P0751 or P0753
    • No 2-3 SS Valve DTCs P0756 or P0758
    • No TFP Val. Position Sw. DTC P1810
    • No TCC PWM Sol. Valve DTC P1860
    • The engine speed is greater than 450 RPM for 8 seconds.
    • Not in fuel cutoff
    • The engine torque is 50-450 lb ft.
    • The gear range is D4.
    • Not in 1st gear
    • The TP angle is 9-35%.
    • The TFT is 20-130°C (68-266°F).
    • The TCC is ON for 5 seconds.
    • The TCC is at maximum apply for 5 seconds.
    • The TCC slip speed is greater than 130 RPM.
    • All conditions met for 7 seconds

Action Taken When the DTC Sets
    • The VCM inhibits TCC engagement.
    • The VCM commands maximum line pressure.
    • The VCM inhibits 4th gear if the transmission is in hot mode.
    • The VCM freezes shift adapts from being updated.
    • The VCM illuminates the Malfunction Indicator Lamp (MIL).

Conditions for Clearing the MIL/DTC
    • The VCM turns OFF the MIL after three consecutive ignition cycles without a failure reported.
    • A scan tool can clear the DTC from the VCM history. The VCM clears the DTC from the VCM history if the vehicle completes 40 warm-up cycles without a failure reported.
    • The VCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the VCM.

Diagnostic Aids
    • Internal transmission failures could set a DTC P1870.
    • A TFP Valve Position Switch malfunction could set a DTC P1870.

Test Description

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

  1. This step tests the torque converter for slippage while in a commanded lock-up state.

DTC P1870 Transmission Slipping Component

Step

Action

Value(s)

Yes

No

1

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

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

Perform the transmission fluid checking procedure.

Refer to Transmission Fluid Check .

Did you perform the fluid checking procedure?

--

Go to Step 3

Go to Transmission Fluid Check

3
  1. Install the scan tool (tech 1) ®.
  2. Turn ON the ignition, with the engine OFF.

    3. Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and Failure Records. Using the Clear Info function erases the Freeze Frame and Failure Records from the PCM.

  3. Record the Freeze Frame and Failure Records.
  4. Clear the DTCs.
  5. With the engine idling and at normal operating temperature, apply the brake pedal.
  6. Select each transmission range: D1, D2, D3, D4, N, R and P.

    7. Refer to Transmission Fluid Pressure (TFP) Manual Valve Position Switch Logic.

Does each selected transmission range match the scan tool TFP switch A/B/C display?

--

Go to Step 4

Go to Transmission Fluid Pressure Manual Valve Position Switch Resistance Check

4
  1. Install the Scan Tool ®.
  2. With the engine OFF, turn the ignition switch to the RUN position.

    3. 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.
  4. Drive the vehicle in 4th gear with the TCC engaged.

Is the TCC Slip Speed greater than the specified value for 7 seconds?

130 RPM

Go to Step 5

Go to Diagnostic Aids

5
  1. Inspect the Torque Converter Clutch Solenoid Valve (TCC Sol. Valve) for the following problems:
    2. • Internal malfunction (such as sediment or damage)
    • Damaged seals
  2. Inspect the Torque Converter Clutch Pulse Width Modulation Solenoid Valve (TCC PWM Sol. Valve) for the following problems:
    3. • Internal malfunction (such as sediment or damage)
    • Damaged seals

Did you find a problem?

--

Go to Step 14

Go to Step 6

6
  1. Inspect the 1-2 Shift Solenoid Valve (1-2 SS Valve) for the following problems:
    2. • Internal malfunction (such as sediment or damage)
    • Damaged seals
  2. Inspect the 2-3 Shift Solenoid Valve (2-3 SS Valve) for the following problems:
    3. • Internal malfunction (such as sediment or damage)
    • Damaged seals

Did you find a problem?

--

Go to Step 14

Go to Step 7

7

Inspect the valve body assembly for a stuck TCC signal valve.

Refer to Transmission Overhaul , in Unit Repair.

Did you find a problem?

--

Go to Step 14

Go to Step 8

8

Inspect the torque converter assembly for the following problems:

    • Stator roller clutch not holding
    • Internal damage

Did you find a problem?

--

Go to Step 14

Go to Step 9

9

Inspect the oil pump assembly for the following problems:

    • A stuck converter clutch valve
    • The converter clutch valve is assembled backwards
    • A mispositioned converter clutch valve retaining ring
    • A mispositioned pump to case gasket
    • Restricted orifice cup plugs
    • Damaged orifice cup plugs
    • Over-tightened, or unevenly tightened pump body to cover bolts

Refer to Transmission Overhaul , in Unit Repair.

Did you find a problem?

--

Go to Step 14

Go to Step 10

10

Inspect the input housing and shaft assembly for the following problems:

    • Cut turbine shaft O-ring seal
    • Damaged turbine shaft O-ring seal
    • Restricted turbine shaft retainer and ball assembly
    • Damaged turbine shaft retainer and ball assembly

Refer to Transmission Overhaul , in Unit Repair.

Did you find a problem?

--

Go to Step 14

Go to Step 11

11

Inspect the 2-4 band assembly for the following problems:

    • Worn 2-4 band
    • Damaged 2-4 band
    • Mispositioned 2-4 band
    • Misassembled 2-4 band
    • The band anchor pin is not engaged.
    • Restricted apply passages in the 2-4 servo assembly
    • Blocked apply passages in the 2-4 servo assembly
    • Nicks or burrs on the servo pin
    • Nicks or burrs on the pin bore in the case
    • Damaged fourth servo piston
    • Misassembled fourth servo piston
    • Damaged band apply pin
    • Incorrect band apply pin
    • Damaged servo bore in the case
    • Missing piston seals
    • Cut piston seals
    • Damaged piston seals
    • Porosity in the pistons
    • Porosity in the cover
    • Porosity in the case
    • Damaged piston seal grooves
    • Plugged orifice cup plug
    • Missing orifice cup plug

Refer to Transmission Overhaul , in Unit Repair.

Did you find a problem?

--

Go to Step 14

Go to Step 12

12

Inspect the forward clutch assembly for the following problems:

    • Worn clutch plates
    • Porosity in the forward clutch piston
    • Damaged forward clutch piston
    • Missing forward clutch piston inner and outer seals
    • Cut forward clutch piston inner and outer seals
    • Damaged forward clutch piston inner and outer seals
    • Missing input housing to forward clutch housing O-ring seal
    • Cut input housing to forward clutch housing O-ring seal
    • Damaged input housing to forward clutch housing O-ring seal
    • Damaged forward clutch housing
    • Damaged forward clutch housing retainer and ball assembly
    • Forward clutch housing retainer and ball assembly is not sealing.

Refer to Transmission Overhaul , in Unit Repair.

Did you find a problem?

--

Go to Step 14

Go to Step 13

13

Inspect the 3-4 clutch assembly for the following problems:

    • Worn clutch plates
    • Porosity in the 3-4 clutch piston
    • Damaged 3-4 clutch piston
    • Missing 3-4 clutch inner and outer seals
    • Cut 3-4 clutch inner and outer seals
    • Damaged 3-4 clutch inner and outer seals
    • Damaged 3-4 clutch spring assembly
    • Damaged 3-4 clutch apply ring
    • Damaged piston seal grooves
    • Plugged orifice cup plug
    • Missing orifice cup plug

Refer to Transmission Overhaul , in Unit Repair.

Did you find a problem?

--

Go to Step 14

Go to Diagnostic Aids

14

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

  1. Select DTC.
  2. Select Clear Info.
  3. Operate the vehicle under the following conditions:
    4. • Drive the vehicle in D4, with the TCC ON, and a throttle position of 9-35%.
    • Ensure that the TCC Slip Speed is -20 to +20 RPM for at least 12 seconds.
  4. Select Specific DTC. Enter DTC P1870.

Has the test run and passed?

--

System OK

Begin the diagnosis again. Go to Step 1