Error Code P1870 is defined as Transmission Component Slipping.

This error code is a manufacturer-specific trouble code, meaning it does not apply to all vehicles makes. Rather, it applies only to specific vehicle makes, such as GM and Chevrolet. Specification of the definition, troubleshooting, and repairs still vary from one make and model to another.

Definition

With the speed of the engine going over 500 rpm for 5 seconds, Fuel Shutoff inactive, throttle angle from 8.5-35%, Transaxle not in First gear, Transaxle gear range is D4, Transmission Fluid Temperature (TFT) Sensor input 68-266°F, engine torque from 50-200 ft-lbs, engine vacuum 0-105 kPa, Torque Converter Clutch (TCC) commanded on and at Max apply for over 5 seconds, the PCM detects a TCC slip speed of over 200 rpm for over 5 seconds, all conditions met for 3 times with TCC commanded off each time in between cycles.

Common Symptoms

As with other error codes, this code activates the Check Engine light and registers the code to the vehicle’s memory system. In some cases, the vehicle may experience harsh shifting from 1-2 upshift.

Possible Causes

Typically, vehicles of this have been driven more than 20,000 mi (32,000 km) before this condition happens.

The harsh shifting from 1  to 2 is caused by wear and tear in the control valve body. This wear happens in the bore that contains the TCC isolator and regulator valves, which results in poor, or no TCC application. This can be difficult to duplicate when the temperature of the transmission is below 93°C (200°F).

Other possible causes for this code include:

  • Fault in internal transmission
  • Trailer towing may set the code
  • Transmission fluid level

How to Check

As with other codes, diagnosing this code requires a scan tool.

GM and Chevrolet provide a service bulletin for this trouble code. Diagnosis for this code can vary from model and year of the vehicle. Therefore, it is important to follow the diagnosis process carefully and thoroughly and complete each step. If the condition exhibited is resolved without completing every step, then there’s no need to perform the remaining steps. If after following all the steps and the condition remain unresolved, then you can contact your dealer or a licensed technician for further diagnosis.

How to Fix

Common repairs for this code include:

  • Installation of a control valve body with the revised TCC regulator and isolator valves. Make sure you refer to the Parts Information table from the service bulletin.

Note:  If all the following information below is true, then you will have to either rebuild the transmission or replace additional transmission components beyond the control valve body.

  • Transmission operation is normal before transmission reaches operating temperature, or before DTC P1870 is set (no slips, flares, or missing gears).
  • Overheated or not blue torque converter
  • Burnt or no-color transmission fluid
  • The transmission fluid pan contains no abnormal debris (clutch material, bronze, brass, or metal fragments).

Error Code P1870 is a type B code. The conditions that sets this code must happen in on two consecutive trips (ignition cycles, with a drive cycle) before setting a P1870 history code.