Faulty torque converter clutch solenoid or pulse-width-modulated solenoid inside the transmission; Damaged wiring or corroded connector between the control module and the transmission, including the internal wiring harness or pass-through connector; Contaminated, degraded or incorrect level of transmission fluid affecting the solenoid or valve body; Sticking or worn valve body components, such as the TCC control or regulator valve; Low or unstable battery or charging system voltage affecting solenoid control; Fault in the control module driver circuit, or an outdated calibration where the manufacturer has issued an update for this fault.

P1864

Torque Converter Clutch Circuit.

Cadillac
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

P1864 on a Cadillac is a GM-specific code for a fault in the torque converter clutch (TCC) circuit. The transmission or powertrain control module saw an electrical or control problem in the circuit that applies and releases the converter lock-up clutch. The exact trigger conditions and which component is monitored depend on the model, year and transmission, so check the correct service information for the vehicle.

Symptoms

Malfunction indicator lamp or transmission warning lamp on
Torque converter clutch not locking up, or locking up erratically
Worse fuel economy at cruising speed
Engine speed higher than normal at steady motorway speed
Shudder or surge at light throttle
Transmission running warmer than usual

Possible causes

Faulty torque converter clutch solenoid or pulse-width-modulated solenoid inside the transmissionlikely
Damaged wiring or corroded connector between the control module and the transmission, including the internal wiring harness or pass-through connectorlikely
Contaminated, degraded or incorrect level of transmission fluid affecting the solenoid or valve bodypossible
Sticking or worn valve body components, such as the TCC control or regulator valvepossible
Low or unstable battery or charging system voltage affecting solenoid controlpossible
Fault in the control module driver circuit, or an outdated calibration where the manufacturer has issued an update for this faultrare

How to diagnose

Read all stored and pending codes and the freeze frame data, noting speed, load, temperature and voltage when the fault set
Check for related codes, such as other transmission, speed sensor or battery voltage codes, and look up any manufacturer bulletins for the model and transmission
Check transmission fluid level, condition and smell, following the procedure for that transmission
Inspect the wiring and connectors from the control module to the transmission for chafing, water ingress, corrosion and pushed-out pins
Test battery and charging voltage with the engine off and running
Measure the TCC solenoid resistance and check the circuit for short to earth, short to voltage or open circuit, using the specification for the model
Use a scan tool to command the TCC and watch the commanded versus actual slip speed on a road test
If the electrical checks pass, inspect the valve body and solenoid for sticking or wear, as the procedure depends on the transmission

How to fix

Repair or replace damaged wiring, terminals or the connector found in the circuit
Replace the faulty TCC solenoid, following the procedure for the transmission
Correct the fluid level, or change the fluid and filter if it is contaminated or degraded
Repair or replace the valve body or worn internal components if they are sticking or leaking
Repair the battery or charging fault if the voltage is out of range
Replace or reprogram the control module only after the wiring and solenoid are proven good, or if a calibration update is published for this fault

Can I keep driving?

Medium severity

The car can usually be driven for a short time, but it is best to have it fixed soon. A TCC that does not release or apply properly can overheat the fluid and cause further transmission damage, so avoid heavy loads and long journeys until it is checked.

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