GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 1996 🢒 Riviera 🢒 DTC 🢒 DTC P1870 Transmission Component Slipping

DTC P1870 Transmission Component Slipping 3.8L VIN 1

Table 1: DTC P1870 Thumbnail table
Table 2: DTC P1870 Transmission Component Slipping

DTC P1870 Thumbnail table

Range

Overdrive

Gear

2nd

3rd

4th

1-2 Shift Solenoid

OFF

OFF

ON

2-3 Shift Solenoid

ON

OFF

OFF

4th Clutch

--

--

Applied

2nd Clutch

Applied

Applied

Applied

3rd Clutch

--

Applied

Applied, but not effective

3rd Sprag Clutch

--

Holding

Overrun

1/2 Support Roller Clutch

Holding

Overrun

Overrun

Forward Band

Applied

Applied

Applied

  • ON = Solenoid Energized
  • OFF = Solenoid De-energized

Circuit Description

The Powertrain Control Module (PCM) monitors the Torque Converter Clutch (TCC) slip by calculating the difference between the engine speed and the transmission output shaft speed.

When the PCM detects an excessive amount of slip when the TCC is engaged, then DTC P1870 sets. DTC P1870 is a type A DTC.

Conditions for Setting the DTC
  1. No TP DTCs P0122 or P0123
  2. No VSS DTC P0502
  3. No 1-2 solenoid performance DTC P0751
  4. No 1-2 solenoid electrical DTC P0753
  5. No 2-3 solenoid performance DTC P0756
  6. No 2-3 solenoid electrical DTC P0758
  7. No TCC PWM solenoid electrical DTC P1860
  8. No TCC enable solenoid electrical DTC P1864
  9. The engine speed is greater than 500 RPM for 5 seconds.
  10. Not in fuel shut off
  11. The throttle angle is 9-35%.
  12. The transmission is not in first gear.
  13. The transmission gear range is D4.
  14. The transmission fluid temperature is 45-165°C (113-329°F).
  15. The engine torque is 70-270 N·m (50-200 ft lbs.).
  16. The MAP is 0-105 kPa (0-15 psi).
  17. The TCC is commanded ON and at maximum apply for 5 seconds.
  18. The TCC slip is greater than 200 RPM for 5 seconds.
  19. The above conditions must occur three times with the TCC commanded OFF between each occurrence.

Action Taken When the DTC Sets
    • The PCM inhibits TCC operation.
    • The PCM inhibits 4th gear, if the transmission is in the hot mode.
    • The PCM illuminates the Malfunction Indicator Lamp (MIL).

Conditions for Clearing the MIL/DTC
    • The PCM turns OFF the MIL after three consecutive ignition cycles without a failure reported.
    • 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 exists and the ignition is OFF long enough in order to power down the PCM.

Diagnostic Aids
    • Ensure that the vehicle's final drive ratio matches the PCM's calibration.
    • Ensure that the transmission will shift through all four gears with the gear select lever in the D4 range.

Test Description

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

  1. This Step inspects the modulator assembly, which could cause P1870 to set.

    2.

  2. These are the components that could cause P1870 to set.

DTC P1870 Transmission Component Slipping

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

Have you performed the fluid checking procedure?

--

Go to Step 3

Go to Transmission Fluid Check

3
  1. Install the scan tool (tech 1 )®.
  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. Select TCC Slip Speed.
  5. Drive the vehicle with the gear select lever in D4 range. Ensure the TCC engages.

Is the TCC slip speed greater than the specified value?

200 RPM

Go to Step 4

Go to Diagnostic Aids

4

Inspect the following items:

    • The modulator assembly
    • Refer to Line Pressure Check .

Repair the items if necessary.

Did you find and correct a problem?

--

Go to Step 6

Go to Step 5

5

Inspect the following components for the indicated condition:

    • Is the TCC solenoid checkball stuck?
    • Does the TCC apply valve fit poorly?
        Refer to No Torque Converter Clutch Apply
    • Is the converter clutch valve stuck?
        Refer to:
    • Is the regulator valve stuck?
        Refer to:
    • Is the TCC PWM solenoid checkball stuck?
        Refer to Converter Clutch Does Not Release
    • Is the turbine shaft 0-ring seal cut or missing?
        Refer to:
    • Is the torque converter fiber material worn or glazed?

Did you find and correct a problem?

--

Go to Step 8

Go to Step 6

6

Inspect the following components for the indicated condition:

    • Is the 3-4 shift valve stuck?
        Refer to No 3-4 Shift
    • Are the 4th clutch fiber plates burned or damaged?
        Refer to No 3-4 Shift
    • Are the 4th clutch piston seals cut or rolled?
        Refer to No 3-4 Shift
    • Is the driven sprocket support ring rolled or twisted, or is a sleeve worn in the 2nd clutch housing?
        Refer to:
       -  First Gear Only
       -  Harsh or Soft 1-2 Shift Feel
       -  Shudder 1-2 Shift
       -  No 2-3 Shift
    • Are the 2nd clutch fiber plates burned or damaged?
        Refer to:
         First Gear Only or Shudder 1-2 Shift
    • Are the 2nd clutch piston seals cut or rolled?
        Refer to:
         First Gear Only or Shudder 1-2 Shift

Did you find and correct a problem?

--

Go to Step 8

Go to Step 7

7

Inspect the following components for the indicated condition:

    • Are the input shaft seals cut or rolled
        Refer to:
    • Are the 3rd clutch fiber plates burned or damaged?
        Refer to No 2-3 Shift
    • Are the 3rd clutch piston seals cut or rolled?
        Refer to No 2-3 Shift
    • Is the forward band burned or damaged?
        Refer to No Drive in Drive Range
    • Is the forward band apply piston oil seal cut or rolled?
        Refer to:
       -  Delayed Engagement
       -  Slips in Drive
       -  No Drive in Drive Range

Did you find and correct a problem?

--

Go to Step 8

--

8

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. • The transmission fluid temperature is 45-165°C (113-329°F).
    • The throttle position is 9-35%.
    • The engine speed is greater than 500 RPM for 5 seconds.
    • The vehicle is not in fuel shut off.
    • The gear range is D4.
    • The gear is not 1st.
    • The MAP is 0-105 kPa (0-15 psi).
    • The engine torque is 70-270 N·m (50-200 ft lb.).
    • The PCM commands the TCC ON for more than 2 seconds.
    • The TCC slip speed is -10 to +50 RPM for more than 5 seconds.
  4. Select Specific DTC. Enter DTC P1864.

Has the test run and passed?

--

System OK

Begin the diagnosis again. Go to Step 1

DTC P1870 Transmission Component Slipping 3.8L VIN K

Table 1: DTC P1870 Thumbnail table
Table 2: DTC P1870 Transmission Component Slipping

DTC P1870 Thumbnail table

Range

Overdrive

Gear

2nd

3rd

4th

1-2 Shift Solenoid

OFF

OFF

ON

2-3 Shift Solenoid

ON

OFF

OFF

4th Clutch

--

--

Applied

2nd Clutch

Applied

Applied

Applied

3rd Clutch

--

Applied

Applied, but not effective

3rd Sprag Clutch

--

Holding

Overrun

1/2 Support Roller Clutch

Holding

Overrun

Overrun

Forward Band

Applied

Applied

Applied

  • ON = Solenoid Energized
  • OFF = Solenoid De-energized

Circuit Description

The Powertrain Control Module (PCM) monitors the Torque Converter Clutch (TCC) slip by calculating the difference between the engine speed and the transmission output shaft speed.

When the PCM detects an excessive amount of slip when the TCC is engaged, then DTC P1870 sets. DTC P1870 is a type A DTC.

Conditions for Setting the DTC
  1. No TP DTCs P0122 or P0123
  2. No VSS DTC P0502
  3. No 1-2 solenoid performance DTC P0751
  4. No 1-2 solenoid electrical DTC P0753
  5. No 2-3 solenoid performance DTC P0756
  6. No 2-3 solenoid electrical DTC P0758
  7. No TCC PWM solenoid electrical DTC P1860
  8. No TCC enable solenoid electrical DTC P1864
  9. The engine speed is greater than 500 RPM for 5 seconds.
  10. Not in fuel shut off
  11. The throttle angle is 8.5-35%.
  12. The transmission is not in first gear.
  13. The transmission gear range is D4.
  14. The transmission fluid temperature is 20-130°C (68-266°F).
  15. The engine torque is 95-270 N·m (70-200 ft lbs.).
  16. The MAP is 0-105 kPa (0-15 psi).
  17. The TCC is commanded ON and at maximum apply for 4 seconds.
  18. The TCC slip is greater than 200 RPM for 5 seconds.
  19. The above conditions must occur three times with the TCC commanded OFF between each occurrence.

Action Taken When the DTC Sets
    • The PCM inhibits TCC operation.
    • The PCM inhibits 4th gear, if the transmission is in the hot mode.
    • The PCM illuminates the Malfunction Indicator Lamp (MIL).

Conditions for Clearing the MIL/DTC
    • The PCM turns OFF the MIL after three consecutive ignition cycles without a failure reported.
    • 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 exists and the ignition is OFF long enough in order to power down the PCM.

Diagnostic Aids
    • Ensure that the vehicle's final drive ratio matches the PCM's calibration.
    • Ensure that the transmission will shift through all four gears with the gear select lever in the D4 range.

Test Description

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

  1. This Step inspects the modulator assembly, which could cause P1870 to set.

    2.

  2. These are the components that could cause P1870 to set.

DTC P1870 Transmission Component Slipping

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

Have you performed the fluid checking procedure?

--

Go to Step 3

Go to Transmission Fluid Check

3
  1. Install the scan tool (tech 1 )®.
  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. Select TCC Slip Speed.
  5. Drive the vehicle with the gear select lever in D4 range. Ensure the TCC engages.

Is the TCC slip speed greater than the specified value?

200 RPM

Go to Step 4

Go to Diagnostic Aids

4

Inspect the following items:

    • The modulator assembly
    • Refer to Line Pressure Check .

Repair the items if necessary.

Did you find and correct a problem?

--

Go to Step 6

Go to Step 5

5

Inspect the following components for the indicated condition:

    • Is the TCC solenoid checkball stuck?
    • Does the TCC apply valve fit poorly?
        Refer to No Torque Converter Clutch Apply
    • Is the converter clutch valve stuck?
        Refer to:
    • Is the regulator valve stuck?
        Refer to:
    • Is the TCC PWM solenoid checkball stuck?
        Refer to Converter Clutch Does Not Release
    • Is the turbine shaft 0-ring seal cut or missing?
        Refer to:
    • Is the torque converter fiber material worn or glazed?

Did you find and correct a problem?

--

Go to Step 8

Go to Step 6

6

Inspect the following components for the indicated condition:

    • Is the 3-4 shift valve stuck?
        Refer to No 3-4 Shift
    • Are the 4th clutch fiber plates burned or damaged?
        Refer to No 3-4 Shift
    • Are the 4th clutch piston seals cut or rolled?
        Refer to No 3-4 Shift
    • Is the driven sprocket support ring rolled or twisted, or is a sleeve worn in the 2nd clutch housing?
        Refer to:
       -  First Gear Only
       -  Harsh or Soft 1-2 Shift Feel
       -  Shudder 1-2 Shift
       -  No 2-3 Shift
    • Are the 2nd clutch fiber plates burned or damaged?
        Refer to:
         First Gear Only or Shudder 1-2 Shift
    • Are the 2nd clutch piston seals cut or rolled?
        Refer to:
         First Gear Only or Shudder 1-2 Shift

Did you find and correct a problem?

--

Go to Step 8

Go to Step 7

7

Inspect the following components for the indicated condition:

    • Are the input shaft seals cut or rolled
        Refer to:
    • Are the 3rd clutch fiber plates burned or damaged?
        Refer to No 2-3 Shift
    • Are the 3rd clutch piston seals cut or rolled?
        Refer to No 2-3 Shift
    • Is the forward band burned or damaged?
        Refer to No Drive in Drive Range
    • Is the forward band apply piston oil seal cut or rolled?
        Refer to:
       -  Delayed Engagement
       -  Slips in Drive
       -  No Drive in Drive Range

Did you find and correct a problem?

--

Go to Step 8

--

8

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. • The transmission fluid temperature is 20-130°C (68-266°F).
    • The throttle position is 8.5-35%.
    • The engine speed is greater than 500 RPM for 5 seconds.
    • The vehicle is not in fuel shut off.
    • The gear range is D4.
    • The gear is not 1st.
    • The MAP is 0-105 kPa (0-15 psi).
    • The engine torque is 95-270 N·m (70-200 ft lb.).
    • The PCM commands the TCC ON for more than 2 seconds.
    • The TCC slip speed is -10 to +50 RPM for more than 5 seconds.
  4. Select Specific DTC. Enter DTC P1864.

Has the test run and passed?

--

System OK

Begin the diagnosis again. Go to Step 1