Low or degraded transmission fluid (wrong level, burnt, contaminated); Worn clutch packs or bands inside the transmission; Low line pressure from a weak pump, blocked filter or internal leakage; Faulty shift or pressure control solenoid, or sticking valve body; Torque converter clutch slipping or failing; Faulty input or output speed sensor, or damaged wiring and connectors giving false slip readings; Outdated transmission control module calibration where a software update is known for the model.

P1870

Transmission Component Slipping.

Chevrolet
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 Chevrolet means the transmission control module has detected a transmission component slipping. It sets when the measured relationship between engine speed and transmission input or output speed does not match the gear ratio commanded, which points to a clutch, band or torque converter not holding as it should. The exact test conditions and which component is monitored depend on the model and transmission fitted.

Symptoms

Engine revs rise without matching acceleration, especially during upshifts
Delayed or soft engagement when selecting Drive or Reverse
Harsh, flared or shuddering gear changes
Transmission warning light or malfunction indicator lamp on
Car goes into a fixed gear (limp mode)
Burnt smell from the transmission fluid

Possible causes

Low or degraded transmission fluid (wrong level, burnt, contaminated)likely
Worn clutch packs or bands inside the transmissionlikely
Low line pressure from a weak pump, blocked filter or internal leakagepossible
Faulty shift or pressure control solenoid, or sticking valve bodypossible
Torque converter clutch slipping or failingpossible
Faulty input or output speed sensor, or damaged wiring and connectors giving false slip readingspossible
Outdated transmission control module calibration where a software update is known for the modelrare

How to diagnose

Read all stored codes and freeze frame data, noting gear, speed, load and fluid temperature when the code set
Check the transmission fluid level and condition on the correct procedure for the model, looking for a burnt smell, dark colour or debris
Inspect wiring and connectors to the transmission, speed sensors and solenoids for damage, corrosion or leaks
Check for other transmission or engine codes that could cause a misleading slip reading, and fix those first
Compare live input and output speed data and engine speed against the commanded gear to confirm real slip rather than a sensor fault
Check the speed sensors and solenoid resistance against the manufacturer's specification for the model
Carry out a line pressure test and stall or road test as the workshop manual specifies for the transmission
Check for any applicable software update or technical bulletin for the vehicle

How to fix

Correct the fluid level and renew the fluid and filter with the specified type if it is degraded
Repair or replace damaged wiring, connectors or faulty speed sensors
Replace faulty shift or pressure control solenoids, or repair the valve body
Overhaul or replace the transmission if clutches, bands, pump or torque converter are worn
Update the transmission control module calibration only where an update is listed for this fault

Can I keep driving?

High severity

Limit driving and avoid it where possible, as continued slipping can quickly burn clutches and cause expensive internal damage. If the car must be moved, drive gently and for a short distance only, and get it inspected promptly.

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