P1870 on GMC
GM: transmission component slipping, usually at the torque converter clutch
Severity: Inspect soon
When P1870 sets, the computer raises line pressure and stops applying the converter clutch to protect the transmission, so it keeps driving but with harsh shifts. The slip behind it can worsen, so get it inspected soon.
It gets more serious if:
- Not verified: The transmission goes into limp-home mode (stuck in one gear, little power) or will not shift. Regulations require the light in limp-home mode, but we found no source saying whether you must stop
This page covers only what differs on GMC. For what P1870 means, the ranked causes and the test order, see the P1870 guide.
What's different on GMC
GMCYour car
2000–2001 · Sierra 1500
Supported by vehicle dataGM 3047 covers harsh converter clutch apply and/or P1870 on the 4L80E; the Savana and Yukon are also listed. The bulletin is on NHTSA, but whether it is still current is not verified, so it is labelled vehicle data rather than confirmed.
Sources and review
- GM 3047: harsh TCC apply and/or DTC P1870, 4L80E
- Deciphering GM Transmission DTC P1870
- Beyond 1870: GM Converter Codes P0741, P0742 and 1887
- Cal. Code Regs. Tit. 13, § 1968.2 — Malfunction and Diagnostic System Requirements (OBD II)
- Last reviewed
- Written by
- Saurabh K.
- Editorial review
- Pending
- Technician review
- Technician review pending
This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error