Diagnostic Aids
WARNING: This page is about a different car, the 2002 GMC Yukon XL, 2002 GMC Sierra, 2002 Chevrolet Suburban, and 2002 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
A TFP manual valve position switch malfunction can set DTC P1870.
A mechanical failure of the shift solenoids or TCC PWM solenoid valve can set DTC P1870.
Internal transmission failures can result in a DTC P1870.
Sticking or contaminated shift valves may cause intermittent slipping in D4.
DTC P1870 defaults to an elevated line pressure condition which may result in TCC partial apply. This may induce idle surge and engine stall.