Faulty torque converter clutch solenoid (open or shorted winding); Damaged, chafed or corroded wiring between the control unit and the transmission, including the internal harness; Poor connection at the transmission connector or the control unit connector (corrosion, bent or loose pins); Contaminated or degraded transmission fluid affecting the solenoid or its electrical operation; Faulty driver circuit in the powertrain control module; Internal transmission fault causing the clutch circuit to read out of range.

P1864

Torque Converter Clutch Circuit.

Oldsmobile
Powertrain
Manufacturer code
Medium severity

How this code is built

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

What it means

On Oldsmobile models, P1864 is a manufacturer-specific code for a fault in the Torque Converter Clutch (TCC) circuit. The control unit commands the TCC solenoid or circuit and sees an electrical state that does not match the command, such as an open circuit, a short or an out-of-range reading. The exact test and the circuit layout vary by model, engine and transmission, so check the correct wiring diagram for the vehicle.

Symptoms

Malfunction indicator lamp or transmission warning lamp on
Torque converter clutch not locking up, so engine revs are higher at cruising speed
Poorer fuel economy on steady motorway driving
Shudder or surge at light throttle if the clutch applies erratically
Transmission running warmer than normal
Possible stalling or a rough feel when coming to a stop if the clutch stays applied

Possible causes

Faulty torque converter clutch solenoid (open or shorted winding)likely
Damaged, chafed or corroded wiring between the control unit and the transmission, including the internal harnesslikely
Poor connection at the transmission connector or the control unit connector (corrosion, bent or loose pins)likely
Contaminated or degraded transmission fluid affecting the solenoid or its electrical operationpossible
Faulty driver circuit in the powertrain control modulerare
Internal transmission fault causing the clutch circuit to read out of rangerare

How to diagnose

Read all stored codes and freeze frame data, noting speed, load and temperature when the fault set, and check for related transmission or speed sensor codes
Check the transmission fluid level, condition and smell, as the procedure varies by model
Inspect the wiring and connectors at the transmission and control unit for damage, water ingress, corrosion and pin tension
Measure the TCC solenoid resistance at the transmission connector and compare with the specification for that model and transmission
Check the supply and control circuits for open circuit, short to earth and short to voltage using the wiring diagram
Command the TCC on and off with a suitable scan tool and check that the circuit responds and the clutch applies on a road test
Check for a software update or calibration bulletin for the vehicle only if the circuit and solenoid test fine
Clear the code and road test to confirm the fault does not return

How to fix

Replace the torque converter clutch solenoid if its resistance or operation is out of specification
Repair or replace damaged wiring and fix any short or open circuit found
Clean, repair or replace corroded or loose connectors and terminals
Change the transmission fluid and filter if it is contaminated, using the correct specification
Replace or repair the control unit only after the wiring and solenoid are proven good
Carry out internal transmission repair if diagnosis shows a mechanical or hydraulic fault

Can I keep driving?

Medium severity

The car can usually be driven short distances, but the clutch may not lock up, which raises fuel use and transmission temperature. Get it checked soon to avoid overheating the fluid or causing further transmission wear.

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