DTC P1870 Transmission Component Slipping. GMC Truck Safari

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 1999 🢒 Safari - 2WD 🢒 DTC 🢒 DTC P1870 Transmission Component Slipping

Table 1:	DTC P1870 Range Reference Thumbnail 4L60-E
Table 2:	DTC P1870 Transmission Component Slipping

Automatic Transmission Components
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice

DTC P1870 Range Reference Thumbnail 4L60-E

Range	Gear	Shift Solenoid		TCC Solenoid	TCC PWM Solenoid	2-4 Band	Forward Clutch	3-4 Clutch	Torque Converter Clutch
Range	Gear	1-2	2-3	TCC Solenoid	TCC PWM Solenoid	2-4 Band	Forward Clutch	3-4 Clutch	Torque Converter Clutch
Overdrive	4th	ON	OFF	ON	90% (ON)	Applied	Applied	Applied	Applied

Circuit Description

The vehicle control module (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 +50 RPM. The table above indicates solenoid states and transmission components that apply during 4th gear with the TCC commanded ON.

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 Running the DTC

•	No TP sensor DTCs P0122 or P0123.

•	No VSS assembly DTCs P0502 or P0503.

•	No TFT sensor DTCs P0711, P0712 or P0713.

•	No TCC solenoid valve DTC P0740.

•	No 1-2 SS valve DTC P0753.

•	No 2-3 SS valve DTC P0758.

•	No TFP manual valve position switch DTC P1810.

•	No TCC PWM solenoid valve DTC P1860.

•	The engine speed is greater than 450 RPM for 5 seconds.

•	The engine is not in fuel cutoff.

•	The vehicle speed is 48-112 km/h (30-70 mph).

•	The engine speed is 1500-3000 RPM.

•	The speed ratio is 0.69-0.88 (speed ratio is engine speed divided by the output speed).

•	The engine torque is 50-400 lb ft.

•	The engine vacuum is 0-150 kPa.

•	The gear range is D4.

•	The commanded gear is not 1st gear.

•	The TP angle is 9-35%.

•	The TFT is 20-130°C (68-266°F).

•	The shift solenoid performance diagnostic counters are zero.

Conditions for Setting the DTC

DTC P1870 sets if the following conditions occur for three TCC cycles.

•	The TCC is commanded ON for 5 seconds.

•	The TCC is at maximum duty cycle (95%) for 5 seconds.

•	The TCC slip speed is 130-800 RPM for 7 seconds.

Action Taken When the DTC Sets

•	The VCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the conditions for setting the DTC are met.

•	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 stores DTC P1870 in VCM history during the second consecutive trip in which the conditions for setting the DTC are met.

Conditions for Clearing the MIL/DTC

•	The VCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.

•	A scan tool clears the DTC from VCM history.

•	The VCM clears the DTC from VCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.

•	The VCM cancels the DTC default actions when the fault no longer exists and the ignition switch is OFF long enough in order to power down the VCM.

Diagnostic Aids

Internal transmission failures could set a DTC P1870.

Test Description

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

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

DTC P1870 Transmission Component Slipping

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 in Engine Controls

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

Install the Scan Tool .
With the engine OFF, turn the ignition switch to the RUN position.

Important: Before clearing the DTC, 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 VCM.

Record the DTC Freeze Frame and Failure Records.
Clear the DTC.
Drive the vehicle in 4th gear with the TCC commanded ON.

Is the scan tool TCC Slip Speed within the specified range for 7 seconds?

130-800 RPM

Go to Step 4

Go to Diagnostic Aids

Inspect the torque converter clutch (TCC) solenoid valve for the following conditions:

•	Internal malfunction (such as sediment or damage)

•	Damaged seals

Inspect the torque converter clutch pulse width modulation (TCC PWM) solenoid valve for the following conditions:

•	Internal malfunction (such as sediment or damage)

•	Damaged seals

Did you find a condition?

Go to Step 13

Go to Step 5

Inspect the 1-2 shift solenoid (SS) valve for the following conditions:

•	Internal malfunction (such as sediment or damage)

•	Damaged seals

•	Refer to Shift Solenoid Leak Test .

Inspect the 2-3 shift solenoid (SS) valve for the following conditions:

•	Internal malfunction (such as sediment or damage)

•	Damaged seals

•	Refer to Shift Solenoid Leak Test .

Did you find a condition?

Go to Step 13

Go to Step 6

Inspect the valve body assembly for a stuck regulator apply valve.

Refer to Unit Repair.

Did you find a condition?

Go to Step 13

Go to Step 7

Inspect the torque converter assembly for the following conditions:

•	Stator roller clutch not holding

•	Internal damage

Did you find a condition?

Go to Step 13

Go to Step 8

Inspect the oil pump assembly for the following conditions:

•	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 Unit Repair.

Did you find a condition?

Go to Step 13

Go to Step 9

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

•	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 Unit Repair.

Did you find a condition?

Go to Step 13

Go to Step 10

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

•	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 Unit Repair.

Did you find a condition?

Go to Step 13

Go to Step 11

Inspect the forward clutch assembly for the following conditions:

•	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 Unit Repair.

Did you find a condition?

Go to Step 13

Go to Step 12

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

•	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 Unit Repair.

Did you find a condition?

Go to Step 13

Go to Diagnostic Aids

Perform the following procedure in order to verify the repair:

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

•	Drive the vehicle in D4, with the TCC ON, and a throttle position of 9-35%.

•	Ensure that the scan tool TCC Slip Speed is -20 to +50 RPM for at least 7 seconds.

Select Specific DTC.
Enter DTC P1870.

Has the test run and passed?

System OK

Go to Step 1