Low or degraded transmission fluid, or a wrong fluid level; Worn clutch packs or bands inside the transmission; Low line pressure from a worn pump, blocked filter or internal leak; Faulty shift or pressure control solenoid, or a sticking valve body; Worn torque converter clutch or converter fault; Faulty input or output speed sensor, or damaged wiring and connectors giving incorrect speed signals; Faulty transmission control module or outdated calibration (model dependent).

P1870

Transmission Component Slipping.

Cadillac
Powertrain
Manufacturer code
High severity

How this code is built

P: SystemPowertrain
1: Defined byThe manufacturer
8: AreaTransmission
70: FaultThe specific fault in that area

What it means

P1870 on a Cadillac means the transmission control module has detected a transmission component slipping. It sets when the measured gear ratio, worked out from input and output speed signals, does not match the ratio commanded for the selected gear, or when torque converter slip is higher than expected. This points to a hydraulic or mechanical problem inside the automatic transmission, or a fault in a signal it relies on.

Symptoms

Engine revs rise during a gear change without matching acceleration
Delayed or soft engagement when selecting Drive or Reverse
Harsh, flared or erratic shifts
Loss of drive in one or more gears
Transmission warning or check engine light on
Transmission may default to a fixed gear (limp mode)

Possible causes

Low or degraded transmission fluid, or a wrong fluid levellikely
Worn clutch packs or bands inside the transmissionlikely
Low line pressure from a worn pump, blocked filter or internal leakpossible
Faulty shift or pressure control solenoid, or a sticking valve bodypossible
Worn torque converter clutch or converter faultpossible
Faulty input or output speed sensor, or damaged wiring and connectors giving incorrect speed signalspossible
Faulty transmission control module or outdated calibration (model dependent)rare

How to diagnose

Read all stored codes and freeze frame data to see gear, speed, load and temperature when the fault set, and note any other transmission or engine codes
Check the transmission fluid level and condition (colour, smell, debris) using the correct procedure for that model, as some have no dipstick
Inspect wiring and connectors to the transmission, speed sensors and solenoids for damage, corrosion, or fluid ingress
Compare live input speed, output speed, engine speed and commanded gear ratio on a scan tool to find which gear slips
Check for any applicable technical bulletins or calibration updates for the specific model and transmission
Test line pressure against the manufacturer's specification, as the method depends on the transmission fitted
Check torque converter clutch operation and slip in live data
Inspect the fluid pan for excessive clutch material or metal debris

How to fix

Correct the fluid level and replace degraded fluid and filter with the specified type
Repair or replace damaged wiring, connectors or faulty speed sensors
Replace faulty solenoids or repair the valve body
Repair or replace the pump or the leaking seals causing low pressure
Overhaul or replace the transmission, or replace the torque converter, if clutches or the converter are worn
Update the transmission control module calibration only if an outdated one is confirmed as the cause, or replace a confirmed faulty module

Can I keep driving?

High severity

Limit driving, as continued slipping quickly burns clutches and can cause costly internal damage. Have it checked promptly, and avoid towing or heavy loads until it is diagnosed.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.