Chevrolet Astro Problems

Check Engine Light With Code P1870 on Chevrolet Astro

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.

(21 people reported this problem)

Chevrolet Astro Vehicles With This Problem

RepairPal Verified
Average mileage: 150,985 (20,800–270,023)
Drive Trains affected: AWD, RWD
7 model years affected: 1996, 1997, 1998, 1999, more2000, 2002, 2005
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Viewing 1-5 of 5 comments
My van is doing the same thing. It has a Check Engine Light that is always on with a P1870 code stored. The computer seems to reset after every drive cycle (turn the engine off and let it sit for a few minutes), but the transmission enters the so-called "lockup" whenever I spend a significant period of time (more than like 10 minutes) at high speed (above 50mph). After that threshold is reached, the transmission performs very poorly until the engine is shut off. If you stop at a red light, the engine sounds like it's struggling to maintain a normal idle because the transmission is trying not to disengage. Furthermore, when I pulled the transmission dip stick the other day, it looks like it's burning up. The fluid is far from clean and there are deposits all along the dip stick. I have already replaced the valve body, fluid, and filter and the check engine light came right back on when I got on the freeway. Is there another simple fix before going down the complete rebuild road?
Same as the other fellow with a/c running, rough 1-2 shift when engine and tranny warm up to operating temp. Last time this happened was just before regular service of tranny at 160,000. Replaced valve at sametime replaced fluid and filter. No problems if run with a/c off all the time, air temp over 90 degrees Fahrenheit though. Suspect fluid thinning due to temp causing valve malfunction.