96 Tahoe Check Engine Code

[CHARLENE MCGHEE]

MY CHECK ENGINE LIGHT HAS BEEN ON FOR SOME TIME NOW BUT I JUST HAD THE CODE CHECKED AND IT WAS P1870. CAN ANYONE TELL ME WHAT THIS IS?...BESIDES A TRANSMISSION CODE??? THIS IS ON A 96 TAHOE 4X4. ANY HELP WOULD BE GREAT!!
THANKS IN ADVANCE -

[maintainin76]

Apparently there is a TSB on 96 Tahoe transmissions. The TSB is below and mentions the code you said. Might/might not be what is causing the problem.

96 Transmission TSB:
AUTOMATIC TRANSMISSION 1-2 AND OR 2-3 UPSHIFT SLIP/FLARE #66-71-04
SUBJECT: AUTOMATIC TRANSMISSION 1-2 AND/OR 2-3 UPSHIFT
SLIP/FLARE, NO 3RD OR 4TH GEAR, LAUNCH SHUDDER,
DTC P1870 (REVISE VCM WIRING)
MODELS: 1996 CHEVROLET AND GMC C/K, S/T, M/L, G1, G2 AND P3 MODELS
1996 OLDSMOBILE BRAVADA
WITH VCM AND 4L60-E (M30) OR 4L80-E (MT1)
AUTOMATIC TRANSMISSION
CONDITION:
SOME OWNERS MAY COMMENT THAT THE AUTOMATIC TRANSMISSION HAS
EITHER A
SLIP OR FLARE ON THE 1-2 AND/OR 2-3 UPSHIFT, OR NO 3RD OR
4TH GEAR, OR LAUNCH SHUDDER. DTC P1870 MAY ALSO BE STORED
IN THE VCM.
CAUSE:
A POOR INTERNAL GROUND BETWEEN THE TWO CIRCUIT BOARDS OF
THE VCM CAN CAUSE THE VCM TO COMMAND ERRATIC LINE PRESSURE
AT THE PRESSURE CONTROL SOLENOIDS (PCS).
CORRECTION:
USING HARNESS JUMPER WIRE AND INSTRUCTION KIT, P/N 12167310,
REVISE THE WIRING HARNESS AT THE VCM CONNECTOR.
CORRECTIONS WERE MADE TO THE VCM BEGINNING 2/14/96. THE
CORRECTED VCM'S ARE IDENTIFIED WITH SERVICE NUMBER 16244210
ON THE VCM IDENTIFICATION LABEL.
SERVICE PROCEDURE
THE FOLLOWING IS A SUMMARY OF THE INSTRUCTIONS INCLUDED
WITH THE SERVICE KIT:
1. REMOVE THE NEGATIVE TERMINAL FROM THE BATTERY.
2. MOVE THE WIRE LOCATED AT CONNECTOR J3
(WHITE/GRAY/CLEAR), PIN 18 TO CONNECTOR J1 (BLUE), PIN 23.
3. INSTALL THE JUMPER WIRE BETWEEN CONNECTOR J2 (RED),
PIN 26 AND CONNECTOR J3 (WHITE/GRAY/CLEAR), PIN 18.
4. INSTALL THE TAG INCLUDED IN THE KIT AROUND THE VCM
WIRING HARNESS. THIS TAG NOTES THAT THE WIRING HARNESS HAS
BEEN MODIFIED.
5. RECONNECT THE NEGATIVE BATTERY TERMINAL.
ROAD TEST TO VERIFY THAT THE CONDITION HAS BEEN
CORRECTED.
IF ANY OF THE FOLLOWING CONDITIONS ARE NOTED, THE
TRANSMISSION SHOULD BE REPLACED, OR FOR CANADIAN
DEALERS, REPAIRED.
-TRANSMISSION FLUID OXIDATION OR EXCESSIVE SEDIMENT.
-TRANSMISSION SLIP OR FLARE AFTER THIS SERVICE FIX IS
PERFORMED.
-DTC P1870 IS STORED ON A 4L60-E (M30).