Check Engine Light With Code P1870 on GMC 1500 Pickup

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.

RepairPal Verified
Average mileage: 107,000 (107,000–107,000)
Drive Train affected: 2WD
4 model years affected: 1996, 1997, 1998, 1999 more
5 people reported this problem
0 people shared problem details
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