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Welcome, and thanks for using Just Answer. I am Cam, and I will do my best to assist you. When you are finished please click on accept only if you are satisfied. I don't get paid unless you do.Please do not accept if you cannot leave positive feedback. I don't know if you are a tech or a just working on your own vehicle so we may have to fine tune the answer. I only know as much about your problem as you have told me in your post, so my answers will be based on what you tell me so please add all the details you can. About your vehicle, no, replacing the valve body is what the fix is. IF it goes to 100% lock up, you will simply loose the cushion created by a little bit of slip. Bu a little but of slip I mean 5-30 rpm.
#01-07-30-023B: Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body) - (Mar 22, 2002)
This bulletin is being revised to update VIN Breakpoint Date information and revise the Parts Information table. Please discard Corporate Bulletin Number 01-07-30-023A (Section 07 -- Transmission/Transaxle).
Some customers may comment on a harsh 1-2 upshift and the Check Engine Light or Service Engine Soon indicator is illuminated.
Typically, these vehicles will have been driven more than 32,000 km (20,000 mi) before this condition occurs.
The scan tool may show a DTC P1870 set as a history code.
A harsh 1-2 shift or DTC P1870, caused by wear in the control valve body, may be difficult to duplicate when the transmission temperature is below 93°C (200°F).
The condition may be due to wear in the control valve body. This wear occurs in the bore that contains the TCC isolator and regulator valves, and results in poor, or no, TCC apply.
Install a control valve body with the revised TCC regulator and isolator valves. Refer to the Parts Information table below. These valves are used in all transmissions produced after January 15, 2000 (Julian Date 0015), and all of the service parts currently available through GMSPO contain revised TCC regulator and isolator valves.
Important: If all of the following conditions are true, it is not necessary to rebuild the transmission or to replace additional transmission components beyond the control valve body.
Transmission Broadcast Code
CCD, CFD, KBD, WAD, WBD
CHD, CJD, KCD, CMD, CUD, KPD, YDD, FFD, WCD, WHD
TBD,TAD, MSD, MDD
CAD, CBD, KAD
(Includes Police Pkg.)
BFD, BWD, BKD
SHD, TLD, TBD, TAD, MSD, MDD
CCD, CFD, KBD
CJD, CHD, KCD
(L31) 5.0L (L30)
ADD, AFD, AJD, ALD, AWD, CCD, CFD, KBD, CHD, CJD, KCD
(L35) 4.3L (LF6)
TAD, MSD, CAD, CBD, KAD, WBD, SHD
(LN2) 2.2L (L43)
(Includes Police Pkg.) G Van
LHD, LSD, LUD, LPD, KXD, CPD