P1870

Diagnostic Chart:

Wiring Diagram:

Circuit Description

The Powertrain Control Module (PCM) monitors the Torque Converter Clutch (TCC) slip speed. The PCM calculates the difference between the engine speed and the transmission output speed. In D3 drive range with the TCC engaged, the engine speed should closely match the transmission output speed. When the PCM detects excessive slip of the TCC, the forward clutch, and the direct clutch when the TCC is engaged in 3rd gear, then DTC P1870 sets. DTC P1870 is a type B DTC.

Conditions for Setting the DTC

^ No Throttle Position (TP) sensor DTCs P0122 or P0123.

^ No Vehicle Speed Sensor Assembly (VSS Assy.) DTCs P0502 or P0503.

^ The engine speed is 1500-4000 RPM.

^ MAP is less than 70 kPa.

^ The throttle angle is 9-50%.

^ The Torque Converter Clutch (TCC) is On for 3 seconds.

^ The TCC slip speed is greater than 150 RPM.

^ The vehicle speed is 56-104 km/h (35-65 mph).

^ The speed ratio is 0.95-1.40.

^ All of the above conditions are met for 8 seconds and 2 TCC engagement cycles.

Action Taken When the DTC Sets

^ The PCM inhibits TCC engagement.

^ 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

^ Verify that the final drive ratio is correct for the vehicle.

^ Check for overloading or trailer towing in excess of vehicle capacity.

Test Description

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

2. This Step tests for excessive torque converter slip while the TCC is engaged.

6. Low fluid level may be causing the slipping.

9. Low line pressure may be causing the slipping.