DTC P1870 Transmission Component Slipping 5.7L and 7.4L Gas
| Table 1: | 4L80-E Range Reference, modified for DTCs P1870 & P1871 |
| Table 2: | P1870 |
Range | Gear | 1-2 Sol | 2-3 Sol | Fourth Clutch | Overrun Clutch | O/D Roller Clutch | FWD Clutch | Direct Clutch | Front Band | Interm. Sprag Clutch | Interm Clutch | Lo Roller Clutch | Rear Band |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Overdrive | 1st | On | Off | -- | -- | H | A | -- | -- | * | -- | H | -- |
2nd | Off | Off | -- | -- | H | A | -- | -- | H | A | O | -- | |
3rd | Off | On | -- | -- | H | A | A | -- | O | A | O | -- | |
4th | On | On | A | -- | O | A | A | -- | O | A | O | -- | |
| |||||||||||||
Circuit Description
The VCM monitors the difference in the engine speed, the turbine speed, and the transmission input speed. In D3 drive range, the engine speed should closely match the turbine speed. IN D4 drive range with the TCC engaged, the TCC slip speed should be -20-+20 RPM.
If the VCM detects an excessive transmission slip between the turbine shaft and the fourth gear planetary gear set when the TCC is engaged, then DTC P1870 sets. DTC P1870 is a type D DTC. For California emissions vehicles, 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 TP Sensor DTCs P0121, P0122, or P0123. |
| • | No VSS DTC P502. |
| • | No ISS sensor DTCs P0716 or P0717. |
| • | No TCC 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 TFP Val. Position Sw. DTCs P1810. |
| • | TFP Val. Position Sw. indicates D4. |
| • | The TP Sensor is 12%-40%. |
| • | The engine torque is 80 lb ft to the following: |
| - | 265 lb ft (470 N·m) (5.7L) |
| - | 355 lb ft (627 N·m) (7.4L). |
| • | The TCC is commanded ON for greater than 1 second. |
| • | The TFT is -10°C to 130°C (14°F-266°F). |
| • | The Shift Solenoid performance counters are clear. |
| • | The TCC is fully locked for greater than 1 second. |
| • | The VCM detects a slip speed of greater than 170 RPM. |
Action Taken When the DTC Sets
| • | The TCC inhibits the TCC engagement. |
| • | The VCM inhibits 4th gear if in hot mode. |
| • | The VCM freezes shift adapts. |
| • | The VCM illuminates the Malfunction Indicator Lamp (MIL) for California emissions vehicles. |
Conditions for Clearing the DTC
- For California emissions vehicles, the VCM turns OFF the MIL after three consecutive ignition cycles without a failure reported.
- A scan tool can clear the DTC from the VCM history. The VCM clears the DTC from the VCM history if the vehicle completes 40 warm-up cycles without a failure reported.
- The VCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the VCM.
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 TP Sensor codes that are present. Then inspect for any transmission DTCs that may have reset. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests the indicated range signal to the actual selected range. A faulty switch can set a DTC P1870.
-
This step tests the torque converter for slippage while in a commanded lock-up state and in fourth gear.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||||||
Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data. Does each selected transmission range match the scan tool TFP Switch display? (Refer to the TFP Val. Position Sw. Range Signal table.) | -- | |||||||
Drive the vehicle in 4th gear while the TCC is engaged. At any time is the TCC Slip Speed greater than the specified value for 10 seconds, while the TCC is engaged above 12% TP? | 170 RPM | Go to System Diagnosis tables | Go to Diagnostic Aids | |||||
4 | In order to verify your repair, perform the following procedure:
Has the test run and passed? | -- | System OK |
