p1870 code persists after full rebuild
Thread Starter
Instructor
Joined: Jul 2025
Posts: 130
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From: San Marcos CA
p1870 code persists after full rebuild
I’ve had the p1870 code in my 2003 a4 c5 for a while now and tried doing the usually fixes such as TCC regulator valve fix, and valve body solenoid replacements, etc with no luck. So I took the next step and rebuilt the whole tranny. New clutches, pistons, seals, servos, drums, torque converter, 2-4 band, etc and completely refurbished the valve body with all new solenoids, wiring harness, etc. that whole transmission is brand spanking new. After all that, tranny still slips 200-300 rpm on inclines, code still pops (no check engine) and trans fluid temps spike. Me and my buddy are completely stumped on this car and don’t know where else to go with getting it fixed. This started happening after installing 3.42 gears into the car and if I recall correctly after I did a pull (pre tune, yes Ik stupid on my part) and the tranny not shifting and hitting the red line. Got the car tinned by a reputable shop for the new gears since than. Could anyone give me anymore insight on what’s going on?? And if my coordination with the redline incident and new gears could js be a red herring?
edit: when I took it all apart, my torque converter, 2-4 band, and input drum were BURNT.
edit: when I took it all apart, my torque converter, 2-4 band, and input drum were BURNT.
Last edited by SattarC5; Jun 3, 2026 at 07:47 PM.
Tech Contributor
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From: Dyer, IN
Thread Starter
Instructor
Joined: Jul 2025
Posts: 130
Likes: 4
From: San Marcos CA
Le Mans Master
Joined: Jul 2010
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Get a different tuner if your present tuner didn't lock the pcm to tune it. If it is locked they might charge you to unlock it. Don't quote me, it's been 20yrs since my buddy did't it.
Thread Starter
Instructor
Joined: Jul 2025
Posts: 130
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From: San Marcos CA
im going to the same shop Monday since they said if its an issue with the tune they will address it free of charge since it was their mistake. How likely would you say the tune is the issue?
