GMC Sonoma Problem Report

GMC Sonoma Check Engine Light With Code P1870

(12 reports)

Vehicles equipped whit a 4 speed automatic transmission may develop a harsh 1-2 shift and/or illumination of the Check Engine Light with code P1870 stored. This can be caused by wear of the bore for the TCC isolator and regulator valves in the valve body. This condition does not commonly occur until the transmission reaches normal operating temperature. If the valve body is worn, replacement will be necessary to correct this concern.

Check engine light came on and had it checked. Code P1870 shows up. Noticed right after it came on that transmission was shifting hard going from 1st to 2nd. Trans. works fine until engine warms up and I have been stop and go city driving.I had the code reset but it came back on after 190 miles then the shift from 1st to 2nd. was harder. -
Check engine light on with p1870 code, (from advance auto). -
Related Items:
I am need to find engine trouble code (check engine light) where can get them ty
Trouble code "transmission module unstable". What are possible fixes? Where is transmission module?
The distributor may develop internal faults. This can cause a rough running engine or stalling...
brake light wont turn off got a new switch and still dont work thay stay on