Trans Code 1870, bad?
Thread Starter
Safety Car
Joined: Apr 2007
Posts: 3,582
Likes: 136
From: SoCal CA
Trans Code 1870, bad?
Was just wondering if anyone out there has gotten a 1870 H C code after a t/c and rear end change? It only happens when cruising around 72-75mph when the converter makes the tranny downshift from 4-3. I guess the computer thinks the converter slips and gives me a code. I could cruise below that speed all day on the freeway with no problem thats why I know it has to do with the converters flashpoint. Anyway to keep it from coming back? BTW, converter is a Yank3600 and 3.42 gears on a 2002 A4 coupe.
Drifting
Joined: Nov 2006
Posts: 1,682
Likes: 2
From: Plano Texas
St. Jude Donor '08
yes I was getting that code when I went from my 3.15 to 3.42 gears. Here is a thread I started in the tuning section:
http://forums.corvetteforum.com/show....php?t=1986164
http://forums.corvetteforum.com/show....php?t=1986164
Team Owner
Joined: Apr 2001
Posts: 54,204
Likes: 180
From: S.W. Ohio. . . . . . NRA Life Member
did you get reprog'd... properly reprog'd ???
the P1870 code says the RPM is too high for the MPH you're traveling. It only sets this code when in 4th with the TC locked... so that's why you're seeing it mainly on the highway - crusing.
This is almost a given when upgrading rear axle ratios on the A4 unless you have a few PCM program changes done.
First the PCM commands a couple "unlock and relock" commands to the converter to see if the problem clears up. If this doesn't clear things up; then the PCM will start increasing line pressure in an attempt to eliminate the "slippage" (whether it's real slippage, or falsely reported slippage due to your real axle ratio upgrade). SOO HIGH PRESSURE that you migh experience neck-breaking shifts.
the P1870 code says the RPM is too high for the MPH you're traveling. It only sets this code when in 4th with the TC locked... so that's why you're seeing it mainly on the highway - crusing.
This is almost a given when upgrading rear axle ratios on the A4 unless you have a few PCM program changes done.
First the PCM commands a couple "unlock and relock" commands to the converter to see if the problem clears up. If this doesn't clear things up; then the PCM will start increasing line pressure in an attempt to eliminate the "slippage" (whether it's real slippage, or falsely reported slippage due to your real axle ratio upgrade). SOO HIGH PRESSURE that you migh experience neck-breaking shifts.
