A/T - 4L60-E DTC P1870 Diagnosis
File In Section: 07 - Transmission/TransaxleBulletin No.: 99-07-30-005
Date: March, 1999
INFORMATION
Subject:
Component Slipping/DTC P187O - Diagnosis
Models:
1996 Buick Roadmaster
1996 Cadillac Fleetwood
1999 Cadillac Escalade
1996-99 Chevrolet Camaro, Corvette
1996-99 Oldsmobile Bravada
1996-99 Pontiac Firebird
1996-99 Chevrolet and GMC C/K, M/L, S/T, G Models with Hydra-matic 4L6O-E (RPO M30)
Description
Many technicians experience difficulty when diagnosing 1996-1999 4L60-E transmissions with a DTC P1870 (Transmission Component Slipping).
The purpose of this bulletin is to provide assistance for technicians that have already completed the DTC P187O diagnostic table in the Service Manual. This bulletin will provide a diagnostic strategy for solving DTC P1870 concerns as well as give some of the most common causes for a DTC P1870.
General Information
Important:
^ Chevrolet Camaro, Pontiac Firebird with 3.8L V6 Engine experiencing a slip condition at 70-90 km/h (45-55 mph) when the TCC applies should refer to Corporate Service Bulletin 77-71-70A for calibration re-flash.
^ 1996 Chevrolet and GMC C/K, M/L, S/T, G Models, and 1996 Oldsmobile Bravada with VCM and 4L60-E (RPO M30) with a slip or flare on the 1-2 and/or 2-3 upshift, or no 3rd or 4th gear, or launch shudder should refer to Corporate Service Bulletin 66-71-03A to ensure that a poor internal ground in the VCM does not exist.
^ A DTC P1870 indicates that a mechanical malfunction exists. If any other DTC's set along with a DTC P1870, then diagnose those first. A DTC P1860 (TCC PWM Solenoid Circuit Electrical) will set if a TCC PWM solenoid circuit failure exists. A DTC P0740 (TCC Enable Solenoid Circuit Electrical) will set if a TCC enable solenoid circuit failure exists.
^ When attempting to duplicate DTC P1870, it is critical that a normal operating temperature of 82°C (180° F) to 93°C (200°F) be reached. It may be difficult to attain the transmission temperature required to adequately cause the DTC to duplicate. Allow the vehicle to idle to assist in warming the powertrain.
^ Optimum speed to duplicate the DTC P1870 is between 89 km/h (55 mph) and 107 km/h (63 mph).
^ Commanding the TCC ON and OFF several times with the Tech is critical to monitoring slip when sticky valves in the valve body are suspect.
^ If the customer brought in the vehicle for a temporary harsh 1-2 shift and no driveability concerns are seen during a test drive, then remember that a harsh 1-2 is a result of the PCM commanding maximum line pressure from recognizing a DTC P1870.
^ The PCM must recognize that a DTC P1870 has set in two consecutive key cycles to illuminate the MIL. If a DTC P1870 is not recognized on a second key cycle. then normal line pressure returns.
^ Vehicles should be inspected for correct tire size, axle ratio, or calibration.
Diagnostic Approach
Slip Check Procedure
This procedure will assist in isolating what area of the transmission is causing your slip, either the TCC system or internal transmission components. After you have isolated the origin of the slip, then utilize the TCC System Symptom Table or the Internal Transmission Symptom Table of this bulletin for most common concerns.
To check for a TCC system concern
TCC slip can occur either hot or cold or in both conditions. First, perform the following test at cold transmission temperatures, then perform the same test at normal operating temperature. Ideal slip from the transmission with the TCC applied is 50 RPM or less under light to normal throttle, no heavy engine load or hard accelerating conditions.
1. Use the Tech II scan tool to monitor TCC slip while driving the vehicle in 4th gear at steady speed with the TCC commanded ON.
2. When the TCC is applied or released (release the TCC with brake pedal, not the scan tool - release the TCC by lightly applying the brake pedal while simultaneously maintaining a steady throttle position), the slip speed should drop or rise 150-300 RPM. If the slip speed does not drop, then the DTC P1870 is being caused by the torque converter system.
To check for an Internal transmission concern
Slip should be checked in every gear to isolate in which gear the slip may be occurring. Drive the vehicle in each forward gear range D1, D2, D3 and D4. Command the TCC ON with the Tech in each gear and monitor slip speed.
Important:
Vehicle speed must be over 11 km/h (7 mph). Some TCC slip is normal when the TCC applies directly after 11 km/h (7 mph) is reached. If the slip speed remains constant from gear to gear, then the condition is most likely TCC related. Example: Slip speed is higher in second and fourth gear than in third gear. This would lead a technician to a possible slipping band.
Important:
These symptom tables are to be used when the following symptoms are associated with a DTC P1870.
TCC System Symptom Table
Service Information
Refer to the appropriate Service Manual for replacement procedures.
Warranty Information
Labor Code:
Refer to Labor Time Guide for correct labor operation. Please use the closest available labor operation for the diagnosis performed.