P189A

Code

Generic P — Powertrain

Torque Converter Clutch (TCC) Solenoid A Circuit Fault

Brand: Generic

Type: P — Powertrain

Views: UK: 6 EN: 7 RU: 7

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Page language: EN

Causes

Open or short in TCC Solenoid A wiring (connector, harness)
Corroded/loose connector or poor ground
Failed TCC solenoid (coil short or open)
Low or dirty transmission fluid / internal valve sticking
Blown fuse or faulty relay supplying solenoid
Faulty PCM/TCM driver/output (less common)

Symptoms

MIL / Check Engine Light illuminated
Torque converter lockup not engaging or disengaging incorrectly
Transmission shudder, slip, or harsh engagement at cruise
Poor fuel economy (no lockup at highway speeds)
Erratic idle or driveability issues when torque converter should lock
Possible limp-home mode or reduced shift quality

What to check

Read and record freeze frame, pending codes and live data with a scan tool
Visually inspect solenoid connector and wiring for damage, corrosion, and proper seating
Check transmission fluid level and condition (dark/contaminated fluid can cause valve sticking)
Verify battery/charging system voltage (should be ~12–14.5 V) during tests
Check relevant fuses and relays for the transmission solenoid circuits
Measure solenoid coil resistance at the connector and compare to spec

Signal parameters

Supply voltage: battery voltage (~11–14.5 V) present at feed terminal with key ON
Ground: PCM/TCM provides switched ground or ground reference when commanded
Coil resistance (typical): roughly 6–30 ohms depending on vehicle — check manufacturer spec
Command signal: switched ground or PWM from PCM; duty cycle variable 0–100% when modulating lockup
PWM frequency: commonly tens to a few hundred Hz (vehicle-specific)
Current draw: typically under 2 A when energized (measure if spec available)

Diagnostic algorithm

Verify the code: connect a scan tool, read stored, pending and freeze-frame data. Note operating conditions when code set.
Visual inspection: examine connector, wiring harness, and transmission case for damage, corrosion, or fluid contamination. Repair any obvious damage.
Electrical checks (key OFF): unplug solenoid connector and measure coil resistance to ground and between terminals; compare to spec. Check for open/short to battery and to ground.
Power/ground check (key ON, engine OFF): verify battery feed at the solenoid connector and a good ground path. Check related fuses/relays.
Dynamic test (engine running): backprobe connector, command TCC Solenoid A ON/OFF with scan tool and observe voltage/PWM and current. Look for expected switching and duty change; note values and compare to signal_params.
Wiggle/strain test while observing live data to find intermittent shorts or opens in harness.
If wiring and connector test good but solenoid fails to respond electrically, apply known-good 12 V (bench test) to solenoid briefly to confirm mechanical operation (observe movement or current change) — use caution and follow vehicle-specific procedures.
If solenoid bench tests OK but circuit shows abnormal behavior under command, suspect PCM/TCM driver; confirm by swapping with identical solenoid (if applicable) or consulting manufacturer-specific tests before replacing control module.
If solenoid is faulty or internal valve stuck, replace solenoid and/or perform necessary transmission service (filter/fluid change, valve body service) and retest.
Clear codes and perform a road test under the conditions that previously set the code to confirm repair. Re-scan for return of code.

Likely causes

Damaged pin, broken wire, or chafed harness to the TCC solenoid
Corrosion or water intrusion at the solenoid connector causing intermittent contact
Solenoid coil internal failure causing abnormal resistance or intermittent short
Failed internal transmission valve or contamination preventing proper solenoid response
Blown fuse or relay in the solenoid feed circuit
PCM/TCM output driver failure (verify after eliminating wiring and solenoid faults)