DTC P1870 Transmission Component Slipping. Buick Century 1997

Go to Step 5

Inspect the following components for the indicated condition:

•	Is the TCC solenoid checkball stuck?

•	Does the TCC apply valve fit poorly?

•	Is the converter clutch valve stuck?

•	Is the regulator valve stuck?

•	Is the TCC PWM solenoid checkball stuck?

•	Is the turbine shaft 0-ring seal cut or missing?

•	Is the torque converter fiber material worn or glazed?

Was the condition found and corrected?

Go to Step 6

Inspect the following components for the indicated condition:

•	Is the 3-4 shift valve stuck?

•	Are the 4th clutch fiber plates burned or damaged?

•	Are the 4th clutch piston seals cut or rolled?

•	Is the driven sprocket support ring rolled or twisted, or is a sleeve worn in the 2nd clutch housing?

Harsh or Soft 1-2 Shift Feel

•	Are the 2nd clutch fiber plates burned or damaged?

•	Are the 2nd clutch piston seals cut or rolled?

Was the condition found and corrected?

Go to Step 7

Inspect the following components for the indicated condition:

•	Are the input shaft seals cut or rolled?

•	Are the 3rd clutch fiber plates burned or damaged?

•	Are the 3rd clutch piston seals cut or rolled?

•	Is the forward band burned or damaged?

•	Is the forward band apply piston oil seal cut or rolled?

Delayed Engagement

Slips in Drive

Was the condition found and corrected?

Begin the diagnosis again. Go to Step 1

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

Select DTC.
Select Clear Info.
Operate the vehicle under the following conditions:

•	The transmission fluid temperature is 20-130°C (68-266°F).

•	The throttle position is 14-35%.

•	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 engine torque is 70-230 N·m (50-170 lb ft).

•	The PCM commands the TCC ON for more than 5 seconds.

•	The TCC slip speed is -20 to +50 RPM for more than 5 seconds.

•	The speed ratio is 0.70-0.995.

•	The engine speed is 800-1500 RPM.

•	The vehicle speed is 56-120 km/h (35-75 mph).

Select Specific DTC. Enter DTC P1870.

Has the test run and passed?

System OK

DTC P1870 Transmission Component Slipping 3.8L

Table 1:	DTC P1870 Thumbnail table
Table 2:	DTC P1870 Transmission Component Slipping (3.8L)

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 B DTC.

Conditions for Setting the DTC

No TP DTCs P0122 or P0123.
No VSS DTCs P0502 or P0503.
No TCC enable solenoid electrical DTC P0740.
No 1-2 solenoid performance DTC P0751.
No 1-2 solenoid electrical DTC P0753.
No 2-3 solenoid performance DTC P0756.
No 2-3 solenoid electrical DTC P0758.
No TCC PWM solenoid electrical DTC P1860.
The engine speed is greater than 500 RPM for 5 seconds.
Not in fuel shut off.
The throttle angle is 8-35%.
The transmission is not in first gear.
The transmission gear range is D4.
The transmission fluid temperature is 20-130°C (68-266°F).
The engine torque is 70-230 N·m (50-170 lb ft).
The TCC is commanded ON and at maximum apply for 3 seconds.
The engine speed is 800-5000 RPM.
The vehicle speed is 56-120 km/h (35-75 mph).
The speed ratio is 0.7-0.995.
The TCC slip is 200-1500 RPM for 8 seconds.

The above conditions must occur 3 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) after two consecutive trips with a failure reported.

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 table.

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

These are the components that could cause P1870 to set.

DTC P1870 Transmission Component Slipping (3.8L)

Step

Action

Value(s)

Yes

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

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

Have you performed the fluid checking procedure?

Go to Step 3

Go to Transmission Fluid Check

Install the Scan Tool ®.
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.

Record the DTC Freeze Frame and Failure Records.
Select TCC Slip Speed.
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

Inspect the following items:

•	The modulator assembly.

•	Refer to Line Pressure Check

Repair the items if necessary.

Was a condition found and corrected?

Go to Step 5

Inspect the following components for the indicated condition:

•	Is the TCC solenoid checkball stuck?

•	Does the TCC apply valve fit poorly?

•	Is the converter clutch valve stuck?

•	Is the regulator valve stuck?

•	Is the TCC PWM solenoid checkball stuck?

•	Is the turbine shaft 0-ring seal cut or missing?

•	Is the torque converter fiber material worn or glazed?

Was a condition found and corrected?

Go to Step 6

Inspect the following components for the indicated condition:

•	Is the 3-4 shift valve stuck?

•	Are the 4th clutch fiber plates burned or damaged?

•	Are the 4th clutch piston seals cut or rolled?

•	Is the driven sprocket support ring rolled or twisted, or is a sleeve worn in the 2nd clutch housing?

Harsh or Soft 1-2 Shift Feel

•	Are the 2nd clutch fiber plates burned or damaged?

•	Are the 2nd clutch piston seals cut or rolled?

Was a condition found and corrected?

Go to Step 7

Inspect the following components for the indicated condition:

•	Are the input shaft seals cut or rolled?

•	Are the 3rd clutch fiber plates burned or damaged?

•	Are the 3rd clutch piston seals cut or rolled?

•	Is the forward band burned or damaged?

•	Is the forward band apply piston oil seal cut or rolled?

Delayed Engagement

Slips in Drive

Was a condition found and corrected?