If you own a late-1990s era Chevrolet S-10 Blazer, then you can expect at some point the check engine light will come on from a P1870 repair code. When you look up this code you will discover it is caused by "transmission component slippage". Thankfully, there is one common cause for this code and a fix that doesn't require a complete rebuild or replacement of your rig's transmission.
The GM 4L60E Transmission and Its Defective Clutch Piston
The General Motors 4L60E transmissions from the late 1990s installed in Blazers, Jimmy's, and other GM trucks all have a structural defect that causes the very common P1870 repair code to pop up eventually. The structural defect is an undersized clutch piston that is prone to breaking as the transmission wears from age.
The clutch piston is one of the pistons the transmission uses to shift from one gear to another. When the piston breaks, then transmission fluid will leak into the piston's bore on the valve cover and the vehicle's computer will lock the piston in place and the check engine light will come on in the cabin.
When the clutch piston is locked, it can block the flow of fluid through the transmission and this will cause the fluid's temperature and pressure to rise dangerously high. Without replacing the clutch piston, your transmission will eventually overheat and stop working.
The Importance of Resetting the P1870 Repair Code
If your Blazer throws the P1870 code while you are driving, it is very important you pull over, allow the transmission to cool down, and use a scan tool to reset the code. Blazers of this vintage all use an OBD2 scan tool and you can purchase one online for very little money.
Resetting the code is vital because it unlocks the piston and allows the transmission's fluid temperature and pressure to return to normal. While you should avoid driving your vehicle with a broken clutch piston, resetting the code goes a long ways towards preventing further damage if you must drive a bit before you can get into the transmission shop.
The Transmission Fix to Eliminate the P1870 Code
Thankfully, since the clutch piston is a known problem with this G.M. transmission, there is a new retrofitted piston your local transmission shop can install into the valve cover. The new piston is thicker and made of a stronger metal so it won't break.
Share29 May 2018
You know that little light that looks like an oil can coming on is a bad thing? Well, my daughter apparently didn't know that it meant that you should stop driving the car and get it into a repair shop immediately. My daughter continued to drive the car without telling me that that little light was on. She said that she thought that it was on for about three weeks before her car died along the road. What damage does that cause? How expensive are those repairs? Visit through our blog of repairing the vehicle that was once perfect but died because that little light was ignored.