P1870

Diagnostic Chart:

Description:

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) monitors the difference in the engine speed, the turbine speed, and the Automatic Transmission In put Shaft Speed (A/T ISS). In D3 drive range with the torque converter clutch engaged, the engine speed should closely match the input shaft speed (turbine speed). In D4 drive range with the TCC engaged, the TCC Slip Speed should be -25 to +30 RPM.
If the PCM detects an excessive slip in the TCC and/or the fourth gear clutch with the TCC engaged, then DTC P1870 sets. DTC P1870 is a type B 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 A/T ISS Sensor DTCs P0716 or P0717.
^ No Output Speed Shaft (OSS) Sensor DTCs P0722 or P0723.
^ No TCC PWM Sol. Valve DTCs P0741, P0742 or P1860.
^ No 1-2 SS Valve DTCs P0751 or P0753.
^ No 2-3 SS Valve DTCs P0756 or P0758.
^ No TFP Val. Position Sw. DTCs P1810.
^ The gear range is D4.
^ The APP Angle 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 is 40 km/h (25 mph).
^ The Shift Solenoid performance fail counters are clear.
^ The engine torque is 75-352 N.m (60-280 lb. ft).
^ The PCM detects a slip speed of 140-500 RPM.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM commands maximum line pressure.
^ The PCM 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. The PCM turns OFF the MIL after three consecutive ignition cycles without a failure reported.
2. 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.
3. 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.
^ Sticking shift valves or contamination may cause intermittent slipping in D4.
^ First diagnose and clear any engine DTCs that are present. Then inspect for any transmission DTCs that may have reset.
^ DTC P186O TCC PWM Solenoid Electrical 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.
3. This step tests the indicated range signal to the actual selected range. A faulty TFP Valve Position Switch can set a DTC P1870.
4. This step tests for proper transmission line pressure.
5. This step tests for slippage while in a commanded lock-up state and in fourth gear; and confirms that the fault is present.
6. This step tests the torque converter for slippage while in a commanded lock-up state and in third gear.
7. This step tests for a sticking shift valve.