Faulty TCC PWM solenoid (open or shorted coil, or internal resistance out of specification); Damaged, chafed or corroded wiring between the solenoid and the control module, including the internal transmission harness; Poor connection at the transmission connector, with corroded, bent or loose terminals, or fluid contamination in the connector; Contaminated or degraded transmission fluid affecting the solenoid or its electrical operation; Low or incorrect battery or charging system voltage causing circuit faults to be flagged; Faulty powertrain or transmission control module driver circuit; Outdated control module calibration where a software update is known to address the fault on that model.

P1860

TCC PWM Solenoid Circuit Electrical.

GM
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 GM vehicles means the control unit has detected an electrical fault in the torque converter clutch (TCC) pulse width modulated solenoid circuit. The module commands the solenoid and monitors the circuit, and it set the code because the voltage or current did not match what it expected, which points to an open circuit, short or high resistance in the solenoid or its wiring.

Symptoms

Check engine light or transmission warning light on
Torque converter clutch not locking up, so engine revs stay higher at cruising speed
Worse fuel economy than usual
Shuddering or surging at steady speeds
Transmission running in a default or limp mode with firm or restricted shifts
Slight overheating of the transmission fluid on long journeys

Possible causes

Faulty TCC PWM solenoid (open or shorted coil, or internal resistance out of specification)likely
Damaged, chafed or corroded wiring between the solenoid and the control module, including the internal transmission harnesslikely
Poor connection at the transmission connector, with corroded, bent or loose terminals, or fluid contamination in the connectorlikely
Contaminated or degraded transmission fluid affecting the solenoid or its electrical operationpossible
Low or incorrect battery or charging system voltage causing circuit faults to be flaggedpossible
Faulty powertrain or transmission control module driver circuitrare
Outdated control module calibration where a software update is known to address the fault on that modelrare

How to diagnose

Read all stored codes and freeze frame data, noting when the fault set and whether other transmission or voltage codes are present
Check battery condition and charging voltage, as low voltage can cause false circuit faults
Inspect the transmission connector and external wiring for chafing, heat damage, corrosion, bent pins and fluid ingress
Check the transmission fluid level and condition, looking for a burnt smell, dark colour or debris, following the procedure for that model
Measure the solenoid resistance at the transmission connector and compare it with the manufacturer specification for the specific transmission
Check the control circuit for continuity, short to earth and short to voltage between the connector and the control module
Use a scan tool with bi-directional control to command the TCC solenoid and watch the response, where the model supports it
Check for applicable software updates or technical bulletins for the vehicle and transmission

How to fix

Repair or replace damaged wiring and fix any short or open circuit found
Clean, repair or replace the corroded or damaged connector and terminals
Replace the TCC PWM solenoid, or the solenoid assembly where it is not sold separately, once it is confirmed faulty
Change the transmission fluid and filter with the correct specification fluid if it is contaminated or degraded
Repair the battery or charging system fault if low voltage is found
Update the control module calibration only where an outdated one is a known cause for that model, or replace the module if its driver circuit is proven faulty

Can I keep driving?

Medium severity

The car can usually be driven short distances, but lack of torque converter lock-up raises transmission temperature and fuel use, and may cause wear. Get it checked soon, and stop if the transmission overheats, slips or shudders badly.

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