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PO1870 Questions????

12-28-2004, 11:32 PM
Hello everyone, I have had this code pop-up it shows that there is a short between the battery and the transfer case.....I was told that all I needed was to replace the vacuum switch on the transfer case. If anyone knows about this code, or has any suggestions please let me know. Thanks

12-29-2004, 05:11 AM
The code isn't for the transfer case.

DTC P1870 Transmission Component Slipping (4.3L)

There are bulletin about this code:
Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body) #01-07-30-023B - (Mar 22, 2002).
If you need a copy let me know. I'll send it directly to you it's about 4-5 pages long. Or if you want the diagnostis chart for the code.

I also beleive that there is a programing update for this code, but I'm not sure.

04-21-2005, 03:40 PM
Could I get a copy of that?

04-21-2005, 05:28 PM
P1870 typically is a result of worn valve body in transmission (part alone is $700 at dealer for REMANUFACTURED)...

If that IS your problem, and you just want it to go away short-term (and maybe forever), AAMCO and similar can ream it out in one spot and put in a new steel sleeve in the hole for about $200 total. GM says to replace the whole faulty (from design) valve body with a new, improved one. I'm having to do that right now for my 98 Blazer (have the part ordered at dealer cost, luckily, thanks to my dad being in the auto industry). With his free labor, the whole deal is still going to cost me $500, but at least I won't get the other codes and problems too. I've read of at least two other problems people have commonly with our 4L60E transmission that are a result of the crappy valve body wearing (low pressure, blowback, random TCC engage, etc.). It's safer overall to just replace the poorly cast valve body like GM says, but it's cheaper right now to get the quick fix and hope the rest never happen.

The reamer to do the temp fix is over $100, and the kit to repair after reaming is even more:

If I were you, I'd clear the code (can do it for real or just disconnect battery for a few minutes) and see if it comes back. If it comes back, and you get that hard shifting (where it feels like it's giving you whiplash), either replace the valve body like GM says, or I'd get AAMCO or a similar shop to repair it for now. They get the parts in bulk and can spread the reamer costs out over multiple repairs, so you don't need that one-time use of a $100 reamer.

04-21-2005, 06:35 PM
Could I get a copy of that?

Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body) #01-07-30-023B - (Mar 22, 2002)
Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body)
1996 Buick Roadmaster

1996 Cadillac Fleetwood

1999-2000 Cadillac Escalade

1996-2000 Chevrolet Camaro, Corvette

1996-2000 Pontiac Firebird

1996-2000 Chevrolet and GMC Light Duty Truck Models

1996-2000 Oldsmobile Bravada

with 4L60-E Automatic Transmission (RPO M30)

Built Prior to January 15, 2000 (Julian Date 0015)

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 93C (200F).

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.

DTC P1870 is a type B code. The conditions for setting the P1870 DTC must occur on TWO CONSECUTIVE TRIPS (ignition cycles, with a drive cycle) before setting a P1870 history code.
When the conditions for setting DTC P1870 are met (first trip), the PCM commands maximum line pressure and harsh 1-2 shifts are the result.
This may result in a harsh 1-2 shift with no history code if the conditions for setting the DTC required for the second trip are not met, on two consecutive trips (Ignition cycles, with a drive cycle).
When the conditions for setting the DTC are met, on the second consecutive trip, a DTC P1870 is stored as a history code.
When the P1870 code is stored, the PCM will turn on the Service Engine Soon (SES), Check Engine Light (CEL), or Malfunction Indicator Lamp (MIL).

Install a control valve body with the revised TCC regulator and isolator valves. Refer to the Parts Information table below (two pages of parts depending on year, model, and engine, let me know what you have). 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.

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 operation is normal before the transmission reaches operating temperature, or before DTC P1870 is set (no slips, flares, or missing gears).
The torque converter is not blue or overheated.
The transmission fluid is not burned or has no burned odor.
The transmission fluid pan contains no abnormal debris (clutch material, bronze, brass, or metal fragments).

04-21-2005, 08:41 PM

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