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P1860

TCC PWM Solenoid Circuit Electrical.

  • Oldsmobile
  • Powertrain
  • Manufacturer code
  • Medium severity

How this code is built

P
SystemPowertrain
1
Defined byThe manufacturer
8
AreaTransmission
60
FaultThe specific fault in that area

What it means

P1860 on an Oldsmobile means the transmission control module has detected an electrical fault in the torque converter clutch (TCC) pulse-width modulated solenoid circuit. The module commands the solenoid with a varying duty cycle and the current or voltage it sees does not match what it expects, which suggests an open circuit, a short or a failed solenoid.

Symptoms

  • Malfunction indicator lamp on, and possibly a transmission warning lamp
  • Torque converter clutch not locking up, so engine revs stay higher at cruising speed
  • Worse fuel economy on steady motorway driving
  • Shudder or surging at light throttle if the clutch applies erratically
  • Transmission running warmer than usual
  • Harsh or delayed shifts if the module has gone into a default strategy

Possible causes

  • Faulty TCC PWM solenoid (open or shorted coil, or internal wear)likely
  • Damaged, chafed or corroded wiring between the solenoid and the control modulelikely
  • Corroded, loose or contaminated connector at the transmission or internal harness connectorlikely
  • Transmission fluid contamination or fluid leaking into the harness connector, causing poor electrical contactpossible
  • Poor power or earth supply to the control module, or low battery voltagepossible
  • Faulty transmission control module driver circuitrare

How to diagnose

  1. Read all stored and pending codes and record the freeze frame data, noting any other transmission or battery voltage faults
  2. Check the transmission fluid level and condition, looking for burnt smell, debris or fluid in the connector
  3. Inspect the external transmission harness and connector for chafing, heat damage, corrosion, bent pins or fluid ingress
  4. Check battery condition and charging voltage, as low voltage can upset solenoid circuit monitoring
  5. Measure the solenoid coil resistance at the transmission connector and compare it with the specification for that model and transmission
  6. Check the circuit for continuity, short to earth and short to voltage between the connector and the control module, with the module disconnected
  7. Check the module power and earth supplies, and confirm the solenoid is being commanded using a suitable scan tool or oscilloscope
  8. Clear the code and road test, watching whether the TCC command and lock-up operate normally and whether the code returns

How to fix

  • Repair or replace damaged wiring and fix any short or open circuit found
  • Clean or replace corroded or contaminated connectors and terminals, and cure any fluid leak into them
  • Replace the TCC PWM solenoid if its resistance or operation is out of specification, as the access method depends on the transmission fitted
  • Replace contaminated fluid and filter if debris or wear is found, then recheck the solenoid
  • Repair battery, power or earth supply faults to the control module
  • Replace or repair the transmission control module only after the wiring and solenoid are proven good

Can I keep driving?

Medium severity

The car can usually be driven for a short time, but without lock-up the transmission runs hotter and uses more fuel. Get it checked soon to avoid overheating the fluid and causing further wear.

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

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