4L60-E / 4L65-E Automatic Transmission

Circuit Description
The powertrain control module (PCM) 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 +50 RPM.
When the PCM detects excessive TCC slip when the TCC should be engaged, then DTC P1870 sets. DTC P1870 is a type B DTC.

Conditions for Running the DTC
^ No MAF sensor DTCs P0101, P0102 or P0103.
^ No TP sensor DTCs P0122 or P0123.
^ No VSS assembly DTCs P0502 or P0503.
^ No TFT sensor DTCs P0711, P0712 or P0713.
^ No TCC solenoid valve DTC P0740.
^ No 1 - 2 SS valve DTC P0753.
^ No 2 - 3 SS valve DTC P0758.
^ No TFP manual valve position switch DTC P1810.
^ No TCC PWM solenoid valve DTC P1860.
^ The engine speed is greater than 30 RPM for 5 seconds.
^ The engine is not in fuel cutoff.
^ The vehicle speed is 48-112km/h (30-70mph).
^ The engine speed is 1500-3000 RPM.
^ The speed ratio is 0.69-0.88 (speed ratio is engine speed divided by the transmission output speed).
^ The engine torque is 50-400 lb ft.
^ The engine vacuum is 0-105 kPa.
^ The gear range is D4.
^ The commanded gear is not 1st gear.
^ The TP angle is 9-35%.
^ The TFT is 20-130°C (68-266°F).
^ The shift solenoid performance diagnostic counters are zero.

Conditions for Setting the DTC
DTC P1870 sets if the following conditions occur for three TCC cycles.
^ The TCC is commanded ON for 5 seconds.
^ The TCC is at maximum duty cycle (90%) for 3 seconds.
^ The TCC slip speed is 130-800 RPM for 7 seconds.

Action Taken When the DTC Sets
^ The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the conditions for setting the DTC are met.
^ The PCM inhibits TCC engagement.
^ The PCM commands maximum line pressure.
^ The PCM inhibits 4th gear if the transmission is in hot mode.
^ The PCM freezes shift adapts from being updated.
^ The PCM stores DTC P1870 in PCM history during the second consecutive trip in which the conditions for setting the DTC are met.

Conditions for Clearing the MIL/DTC
^ The PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
^ A scan tool clears the DTC from PCM history.
^ The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
^ The PCM cancels the DTC default actions when the fault no longer exists and the ignition switch is OFF long enough in order to power down the PCM.

Diagnostic Aids
Internal transmission failures 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.