P1870

WITH 4L60-E AUTOMATIC TRANSMISSION

DTC P1870 Transmission Component Slipping Diagnostic Chart:

Torque Converter Clutch (TCC):

CIRCUIT DESCRIPTION
The Vehicle Control Module-A (VCM-A) monitors the difference in engine speed and output speed. With transmission in "drive", and Torque Converter Clutch (TCC) engaged, the scan tool should display engine speed closely matching output speed. DTC Type (D).

DTC P187O WILL SET WHEN
- No DTC(s) P0122, P0123, P0502, P0503, P0712, P0713, P0753, P0756, P0758, P1810, P1860 and P1864.
- TCC slip speed greater than 300 RPM.
- Throttle position is between 0% and 35%.
- TCC is engaged.
- In D3, D4.
- All conditions are met for 10 seconds.
- Transmission fluid temp is between 20°C and 115°C (68°F and 239°F).

ACTION TAKEN (VCM-A will default to)
- Inhibit TCC operation.
- Max line pressure.
- Inhibit 4th gear in hot mode.

DTC P1870 WILL PASS WHEN
- The VCM-A will report a "PASS" when TCC slip is less than 300 RPM.
- All enable criteria are met.

DTC P1870 WILL CLEAR DEFAULT ACTION WHEN
The fault condition(s) no longer exist and the ignition switch is cycled "OFF" for five seconds, then "ON."

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This test checks the indicated range signal to the actual selected range. A faulty switch could set DTC P1870.
2. This test checks the torque converter for slippage while in a commanded lock-up state.

DIAGNOSTIC AIDS
- Check for deformed connectors at pass-thru connector.
- DTC P1870 will set when going to default (second gear).
- Refer to Intermittents.
- Refer to Transmissions and Drivetrain. Transmission and Drivetrain
- An intermittent incorrect engine speed signal will set a DTC P1870 if the incorrect signal lasts for greater than 10 seconds.
- A mechanical failure in the 1-2 (A) shift solenoid (stuck "OFF") or 2-3 (B) shift solenoid (stuck "ON"), could set DTC.