Code Definition

P1870 — Transmission component slipping

System: Powertrain  |  Type: Manufacturer-Specific  |  Make: GM

About P1870

P1870 is a manufacturer-specific powertrain diagnostic trouble code recorded for GM vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

P1870 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

DTC P1870 sets when the Transmission Control Module detects excessive slip in a transmission component, typically the torque converter clutch but sometimes an internal clutch pack, even though engagement has been commanded and hydraulic pressure should be applied. The module calculates slip by comparing engine or input speed against turbine and output speed sensor data, and stores the code when the measured slip exceeds the calibrated limit for a set time. On many GM transmissions such as the 4L60E this most often reflects a worn torque converter clutch or wear in the pump and valve body that ...

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