Question about 1996 Pontiac Grand Am
A P1870 code is a General Motors code,and the definition on a scan tool,or diagnostic chart,is "Transmission Component Slipping"I've been rebuilding these units for many years.A slip code can be set in numerous ways,from clutch packs that simply have too much clearance,to a valvebody bore that is so severely worn,it needs reaming,and an oversized valve installed.All are internal problems that have to be addressed with a rebuild,and resetting of all clutch pack clearances,end play clearances, and bushing clearances.What will happen for your car in the near future is,it will start shifting hard,then harder and harder yet,because the computer is trying to overcompensate for the "slip" it is seeing.GM's system of measuring "slip",is shift timing.The vehicle computer monitors how long each upshift takes to complete,in tenths of seconds.If a shift,or multiple shifts start taking 8/10ths,9/10ths,over 1 second,on a consistent basis,the computer will set the P1870 code,illuminate the "check engine" or "srvce engine soon",and will also increase line pressure inside the trans.Whew.
Posted on Jul 09, 2008
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