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GMC 3500 Pickup Problems

Check Engine Light With Code P1870 on GMC 3500 Pickup

Problem Description and Possible Solution

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.

(5 people reported this problem)

GMC 3500 Pickup Vehicles With This Problem

RepairPal Verified
Average mileage: (–)
5 model years affected: 1996, 1997, 1998, 1999, more2000
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