P0732

P0732 sets when the TCM commands 2nd gear and the calculated ratio (input/turbine speed divided by output speed) does not match the expected 2nd gear ratio within tolerance, typical threshold is 5-7% deviation held for 2-5 seconds while in 2nd gear under load. The math: if 2nd gear ratio is 1.62:1, expected input/output ratio at any vehicle speed should be 1.62 plus or minus the threshold, anything outside that window for the dwell time arms the code. This means either the trans is physically slipping in 2nd (clutch or band wear, low line pressure, stuck shift solenoid leaving it in 1st or 3rd), or a speed sensor is reporting incorrectly. Cheapest-first diagnostic ladder: check ATF level and condition on a level surface at the spec temperature (most platforms 95-115F), low or burnt fluid is the root cause more often than any single failed component; hook a pressure gauge to the line pressure tap and verify spec pressure across the throttle range (typical 60-90 PSI at idle in drive, 150-250 PSI at full throttle stall), low line pressure points to a worn pump, leaking pressure regulator, or stuck pressure control solenoid. Ohm the shift solenoids at the case connector (typical 10-25 ohms for on/off solenoids, 4-7 ohms for PWM solenoids) and compare against spec. Expensive misdiagnosis: do not authorize a transmission rebuild on a P0732 until you have ruled out a stuck solenoid and verified line pressure, a stuck shift solenoid B in a 4L60E throws P0732 with a perfectly healthy 2nd gear set, the fix is a $35-80 solenoid versus a $2,500-4,000 rebuild.

Vehicle-specific patterns: 2003-2007 Honda Accord/Odyssey 5AT (BAYA, B7TA) has a famous 2nd-gear-clutch failure pattern from low line pressure and inadequate filter capacity, Honda extended-warranty bulletin and Service Bulletin 04-018 covered many affected VINs; 2004-2010 Toyota Sienna/Highlander with U151E sees 2nd-gear codes from B1 brake apply failure, valve-body solenoid wear is the typical root cause; 2000-2007 GM 4L60E (Silverado, Tahoe, Trailblazer) is famous for the sun-shell splines stripping under 2nd-gear load, a $40 hardened sun shell prevents the failure but installed-cost is a teardown. Estimated repair: $250 to $4,000.