P1860moderate severityPowertrain

TCC PWM Solenoid Circuit Electrical

on 2005 Buick Terraza 3.5L V6 · FWD

What this code means

The PCM/TCM detected a continuous open, short to ground, or short to power in the Torque Converter Clutch (TCC) Pulse Width Modulation (PWM) solenoid valve circuit. The TCC PWM solenoid controls smooth engagement of the torque converter clutch by varying duty cycle. Normal solenoid resistance is 10-16 ohms.

Symptoms

Check Engine Light
Transmission slipping
Harsh shifting
No torque converter lockup
Reduced fuel economy
Bucking feeling at highway speed
Transmission overheating

Common causes

Failed TCC/PWM solenoid (most common)
Broken or corroded wiring to solenoid
Short in wire harness
Faulty PCM/TCM
Poor electrical connection at transmission connector
PCM software needing update

Diagnostic steps

Test TCC PWM solenoid resistance (should be 10-16 ohms)
Check for open, short to ground, or short to power on solenoid circuit
Inspect transmission connector for damage
Clear codes and road test
Test PCM solenoid driver output

Repair notes

Check solenoid resistance first. Replace TCC PWM solenoid if out of spec. Inspect transmission connector and wiring. Solenoid is accessible by removing transmission pan and valve body.

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