P1870

DTC P1870 Transmission Component Slipping

DTC P1870 Range Reference Thumbnail 4L60-E:

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.

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