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DTC codes / GM codes / P1887

P1887 · GMTCC Release Switch Circuit

P1887 on GM vehicles indicates that the torque converter clutch (TCC) release switch circuit has reported an unexpected condition to the transmission control module (TCM). The TCM monitors this circuit to confirm the TCC is actually released when commanded, and it sets the code when the switch signal does not match the commanded state or is out of range.

SystemPowertrain
Code typeGM specific
SeverityMedium
Fix difficultyIntermediate
AreaTransmission

Symptoms you may notice

  • Illuminated check engine light or transmission warning light, often with no other symptoms
  • Harsh or delayed engagement when shifting from Park or Neutral into Drive
  • Engine stumble or shudder at low speeds when the converter clutch is commanded to release
  • Poor fuel economy if the TCC fails to release and the engine stays coupled
  • Transmission may default to a limp-home mode with firm shifts
  • In rare cases, stalling when coming to a stop if the TCC stays applied

Common causes, most likely first

  1. Faulty TCC release switch (pressure switch) on the transmission valve body
  2. Damaged or chafed wiring harness between the switch and the TCM
  3. Corroded or loose electrical connector at the transmission pass-through or switch
  4. Sticking TCC release valve or contaminated valve body
  5. Low or degraded transmission fluid affecting hydraulic release
  6. Failed TCM or internal transmission electrical fault (less common)

How to diagnose and fix it

  1. Verify battery voltage and inspect the transmission wiring harness for obvious damage or corrosion
  2. Scan all modules for related codes and check TCC release switch data on a scan tool while commanding the TCC on and off
  3. Check transmission fluid level and condition; service if contaminated or low
  4. Disconnect the TCC release switch connector and measure resistance across the switch; compare to specification
  5. Backprobe the switch signal circuit at the TCM and confirm voltage changes when the TCC is commanded
  6. If the switch tests faulty, replace the TCC release switch and clear codes
  7. If wiring and switch are good, inspect the valve body for a sticking TCC release valve and repair or replace as needed

TCC release switch diagnosis pitfalls

  • A P1887 can be set by a simple loose connector at the transmission, so always check the pass-through connector before condemning the switch.
  • The TCC release switch is a pressure switch, not a solenoid; testing it with a multimeter is straightforward but requires knowing the expected state when the TCC is applied versus released.
  • Debris in the transmission fluid can cause the release switch to stick, so a fluid service may resolve the code even if the switch itself is fine.
  • Some aftermarket scan tools misreport TCC release switch status, so verify with a factory-level tool or a known-good meter before replacing parts.
  • A failing TCC solenoid can mimic a release switch fault by not applying or releasing pressure correctly, so always command the solenoid and watch switch response together.

Can I keep driving with P1887?

You can usually drive the vehicle with P1887 set, but avoid heavy acceleration and towing until the fault is repaired, because a stuck torque converter clutch can cause stalling or transmission damage. If the vehicle shudders, stalls, or enters limp mode, stop driving and have it diagnosed promptly.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for GM vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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