P1870

Diagnostic Chart:

Description:

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 commanded ON, then DTC P1870 sets. DTC P1870 is a type B DTC.

Conditions for Setting the DTC

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

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

^ No solenoid electrical DTCs P0740, P0753, P0758 or P1860.

^ No 1-2 Shift Solenoid performance DTC P0751.

^ No 2-3 Shift Solenoid performance DTC P0756.

^ Not in fuel shut off.

^ The throttle angle is 14-60%.

^ The transmission is not in first gear.

^ The transmission gear range is D4.

^ The engine coolant temperature is above 40°C (104°F).

^ The TCC is commanded ON, and at maximum apply for more than 8.5 seconds.

^ The engine speed is 1000 - 6000 RPM.

^ The vehicle speed is 40-132 km/h (25-82 mph).

^ The speed ratio is 0.78-1.1.

^ The TCC slip is 200-1500 RPM for 8 seconds.

^ The MAP is 20 - 64 kPa (3 - 11 psi).

The above conditions must occur 3 times with the TCC commanded OFF between each occurrence.

Action Taken When the DTC Sets

^ The PCM illuminates the Malfunction Indicator Lamp (MIL).

^ The PCM inhibits TCC operation.

^ The PCM inhibits 4th gear if the transmission is in the hot mode.

Conditions for Clearing the MIL/DTC

^ The PCM turns OFF the MIL after three consecutive trips 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.

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

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