1998 C5 with P1870 code causing a big headache
Thread Starter
6th Gear
Joined: Sep 2018
Posts: 6
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1998 C5 with P1870 code causing a big headache
Hey Guys. New to the forum. Just a quick history of my car. 1998 C5 I purchased 2 years ago with 205,000kms. It had an engine light on for cam position sensor and P1870(tranny component slippage). Replace the ECM and that fixed the cam position sensor issue but the P1870 still there. Did a tranny service and replaced the valve body and NO Luck. Removed the tranny and did a complete rebuild and new torque converter and still NO LUCK. Removed the tranny for the 2nd time to have it rechecked and also replaced the the torque converter again and AGAIN NO LUCK. I purchased a completely different tranny from a running C5 and also purchased a brand new torque converter from Circle D specialties and once AGAIN NO LUCK. This P1870 will not go away. Looking for some suggestions and some help. Thank
Thread Starter
6th Gear
Joined: Sep 2018
Posts: 6
Likes: 0
When we first decided to drop the tranny At that time I decided to drop the engine as well. We did a cam ,headers ,heads full exhaust and a few other things. When it was done it went straight in for a full tune. The rear end is stock for that year and the torque converter from Circle D is a 3200 stall.
Drifting
Joined: Oct 2002
Posts: 1,773
Likes: 66
From: SoCal
Did your car have a High Stall Converter installed when you bought it and the converters you replaced with it all high stall converters. If so, could be an issue due to the fact that the stock PCM slip speed in 4th gear is looking at 80-800 RPM stall speed. Anything greater or smaller stall speed will trigger the P1870 code. Now if these are all High Stall Converters than those will trigger the code. Your tuner should have gone in and set the variables for the higher stall in the tuning software so it would not set the P1870 code.
Thread Starter
6th Gear
Joined: Sep 2018
Posts: 6
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The 1st torque converter was the original with 2300 stall the 2nd converter was a 2700 stall and now the Circle D is a 3200 stall. All the same symptoms. The tune was done with the 2700 stall. The tranny is not slipping but at cruising it is searching for a gear, and then it pops out of OD and the engine light comes on. Both transmissions and all the Converters are doing the same thing.
Thread Starter
6th Gear
Joined: Sep 2018
Posts: 6
Likes: 0
Hey guys just an update. Received a lot of great info from this forum which lead me to investigate other areas of my car like the rear diff. My car from factory came with 2:73 and after checking my car I found out it had 3:42. At some point someone change it out and never updated the ECM. Well I did that today along with some tranny updates and I’m happy to report the car is all fixed. Thanks again
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