P0742 TCC Stuck On: Causes & Fix (Engine Stalls at Stop)

P0742 means your TCC is stuck ON. The torque converter is locked when it shouldnt be. Result: engine stalls when you come to a stop in gear. Heres why and how to fix it.

Get the parts for this repair
Shop 6L80 Parts →Shop 47RE Parts →

What P0742 means

TCC Stuck On:

  • Converter clutch wont release
  • Truck behaves like manual without pressing clutch
  • Stalls when stopping in gear
  • Different from P0741 (stuck off)

    • Common causes

    #1: TCC solenoid stuck on

  • Most common cause
  • Varnish or coil failure

    • #2: Wiring short to ground

  • PCM continuously commands TCC
  • Wiring chafe to ground

    • #3: Valve body TCC apply valve stuck

  • Bore wear or varnish

    • #4: Brake switch failed

  • Doesnt signal brake pressed
  • TCC doesnt release

    • Diagnosis

    Step 1: Verify code

  • P0742 confirms stuck on

    • Step 2: Test brake switch

  • Brake lights work?

    • Step 3: Disconnect TCC solenoid

  • If stall stops with disconnected = solenoid or wiring

    • Step 4: Resistance check

  • Short = stuck on

    • Cost by cause

    Cheap fixes ($20-$300):

  • Brake switch: $20-$60
  • Wiring repair: $50-$200

    • Mid-tier ($200-$700):

  • TCC solenoid: $200-$500
  • Sonnax TCC kit: $300-$600

    • Why driving stuck-on is bad

    • Stalls dangerous in traffic
    • TCC clutch wears constantly
    • Heat buildup

    Temporary workaround

    • Disconnect TCC solenoid
    • RPMs high at highway
    • No more stalls
    • Limp to shop

    Bottom line

    Most P0742 fixes:

  • TCC solenoid (50%)
  • Wiring (25%)
  • Brake switch (15%)
  • Valve body (10%)

    • Cheapest path:

  • Test brake switch first
  • TCC solenoid next
  • Wiring inspection
  • Valve body last

    • Need TCC solenoid, brake switch, or rebuild parts? Visit our main catalog. TCC solenoids, switches, complete rebuild kits. Free shipping over $70.

    Related: