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GTECH Calibration
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P1864

Torque Converter Clutch Circuit.

  • Saturn
  • 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 Saturn means the powertrain control module has detected a fault in the torque converter clutch (TCC) circuit. The module checks the electrical state of the TCC solenoid or its control circuit and has seen a reading that does not match what it commanded. The exact test and set conditions vary by model, engine and transmission, so confirm them against the correct service information for the vehicle.

Symptoms

  • Malfunction indicator lamp on
  • Transmission stays unlocked, so engine revs sit higher at cruising speed
  • Worse fuel economy on steady motorway driving
  • Shudder or surging at light throttle or steady speed
  • Transmission may run warmer than normal
  • Possible harsh or odd shifts if the module restricts operation

Possible causes

  • Damaged, chafed or corroded wiring to the TCC solenoid (open circuit, short to earth or short to voltage)likely
  • Poor connection at the transmission connector or the powertrain control module connectorlikely
  • Faulty TCC solenoid or TCC pulse-width-modulated solenoid with wrong resistancelikely
  • Fault in the transmission internal wiring harness or pass-through connectorpossible
  • Contaminated or degraded transmission fluid affecting the solenoid or valve bodypossible
  • Faulty powertrain control module driver circuitrare

How to diagnose

  1. Read the stored codes and freeze frame data, noting whether other transmission or speed sensor codes are present, then record and clear only after diagnosis is complete
  2. Check the transmission fluid level, condition and smell, following the procedure for that model
  3. Inspect the wiring between the transmission and powertrain control module for chafing, heat damage, water ingress and corrosion
  4. Check the transmission and control module connectors for bent, pushed-out or corroded pins and poor terminal tension
  5. Measure the TCC solenoid resistance at the transmission connector and compare it with the specification for that transmission
  6. Check the solenoid circuit for supply voltage, earth and control signal, and test for shorts to earth or voltage
  7. Use a scan tool to command the TCC and watch for the expected change in engine speed and slip at cruising speed
  8. Check for any applicable service bulletins or calibration updates for the model and transmission

How to fix

  • Repair or replace damaged wiring and fix any chafed sections, using proper terminal repairs
  • Clean or replace corroded or damaged connectors and terminals
  • Replace the faulty TCC solenoid, following the procedure for that transmission
  • Repair or replace the internal transmission harness or pass-through connector if tested faulty
  • Correct the fluid level or replace contaminated fluid and filter if the condition requires it
  • Replace or reprogram the powertrain control module only after the wiring and solenoid are proven good, or if an updated calibration is a known fix

Can I keep driving?

Medium severity

The car can usually be driven for a short time, but the converter will not lock up, which increases fuel use and transmission heat. Get it checked soon, especially if you see shuddering, slipping or harsh shifts.

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

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