P1870

Diagnostic Chart:

Range Signal Table:

Circuit Description
The PCM monitors the difference in the engine speed and the transmission output speed. In D3 drive range with the Torque Converter Clutch (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. If the PCM detects and excessive TCC slip when the TCC is engaged, then DTC P1870 sets. DTC P1870 is a type A DTC.

Conditions for Setting the DTC
The following conditions are met for 10 seconds with 4th gear commanded and the TCC ON.

^ No engine speed DTC P0335.
^ No Accelerator Pedal Position (APP) Sensor DTCs P0121, P0122, P0123, P0220, P0221, P0222, P0223, P0225, P0226, P0227, P0228.
^ No Input Speed (ISS) sensor DTCs P0716 or P0717.
^ No Output Speed (OSS) Sensor DTCs P0722 or P0723.
^ No TCC Pulse Width Modulated (PWM) Sol. Valve DTCs P0741 or P0742.
^ No 1-2 SS Valve DTCs P0751 or P0753.
^ No 2-3 SS Valve DTCs P0756 or P0758.
^ No Transmission Fluid Pressure (TFP) Val. Position Sw. DTCs P1810.
^ The gear range is D4.
^ The Throttle Position (TP) Sensor is 12-70%.
^ The Transmission Fluid Temperature (TFT) is -10 to +130°C (14-266°F).
^ The engine speed is 1200-3750 RPM.
^ The Vehicle Speed Sensor (VSS) is 40-205 km/h (25-127 mph).
^ The PCM detects a slip speed of 140-500 RPM.
^ The Shift Solenoid performance fail counters are clear.

Action Taken When the DTC Sets

^ The PCM commands maximum line pressure.
^ The TCC inhibits the TCC engagement.
^ The PCM inhibits 4th gear if in hot mode.
^ The PCM freezes shift adapts.
^ The PCM illuminates the Malfunction Indicator Lamp (MIL).

Conditions for Clearing the MIL/DTC

1. 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.
2. 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

^ A TFP Val. Position Sw. malfunction can set DTC P1870.
^ A mechanical failure of the shift solenoids or TCC PWM Sol. Valve can set DTC P1870.
^ Internal transmission failures can result in a DTC P1870.
^ First diagnose and clear any engine DTCs or APP Sensor codes that are present. Then inspect for any transmission DTCs that may have reset.
^ DTC P1860 can cause a DTC 1870 to set. Diagnose the electrical codes first.

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

2. This step tests the indicated range signal to the actual selected range. A faulty switch can set a DTC P1870.
3. This step tests the torque converter for slippage while in a commanded lock-up state and in fourth gear.