#F4a42 transmission leak code
The causes of a P0734 trouble code include a faulty PCM, ECM, or TCM blockage inside the transmission a faulty shift solenoid, dirty or contaminated transmission fluid, or a low transmission fluid condition, and a mechanical transmission failure. And when this data does not match up, a P0734 trouble code is stored. The vehicle's Engine Control Module (ECM), Transmission Control Module (TCM), or PCM, depending on the vehicle make and model, uses information from the transmission speed sensor, calculated against engine speed, to determine the proper gear ratio. The P0734 trouble code develops when there is a problem shifting into fourth gear specifically.
Utilizing the position of the throttle, engine load and speed, as well as vehicle speed, the vehicle computer determines the appropriate gear to shift into to maintain the desired speed and power in an automatic transmission. Some manufacturers allow the adaptations to be learned as the vehicle is driven, others may make you go through a process of engagements or drive cycles, and still others – like this Hyundai – require the use of a capable scan tool.A P0734 trouble code indicates that an abnormality has been detected in the gear ration of one of the automatic transmissions gears, causing the storage of a code in the Powertrain Control Module (PCM) and illumination of the Check Engine Light. Shift adaptations are something we have to take into consideration when repairing today’s transmissions. Even the off-going second clutch shows the three phases instead of a sudden drop. The on- coming overdrive clutch (blue) shows all three phases – servo, torque and inertia – taking place in a little more than a second. Figure 3 shows the same shift after the adaptations were reset. The vehicle had smooth initial engagements, both Neutral to Drive and Neutral to Reverse, and had excellent, smooth upshifts. We had the adaptation reset with a factory scan tool and road-tested the vehicle to adapt to the used transmission’s clutch clearances (ATSG covered this information in its 2009 “blue” seminar book). For some reason the adaptations of the old transmission would cause the second clutch to be reapplied, causing the slight bind during the 2-3 shift. This is probably because the TCM had maxed out the 2-3 shift adaptations in compensating for the third-gear slip.įigure 2 shows the 2-3 shift under light throttle. The shift is short – about 0.5 second – with high pressure at the servo phase and almost no torque phase. You can see the second clutch (green) being released while the overdrive clutch (blue) is coming on. Figure 1 shows the pressure graph during the harsh 2-3 shift. We installed three pressure transducers to record the pressures and confirmed what we had thought all along it appeared like adaptation. The problem seemed to me like a typical adaptation issue. With no codes present we drove the vehicle for about 40 miles, with still no success. All other shifts and initial engagements seemed good with the exception of neutral to drive, which was not hard but was noticeable. We installed the used transmission, and when we road-tested the vehicle we noticed that under normal acceleration it had a very hard 2-3 shift and under light throttle had what appeared to be a slight bind-up on the 2-3 shift. When we informed the customer of his options, he chose a used transmission because of a lack of funds. The customer’s description of the complaint was, “It shifts harsh when cold and sometimes misses the second shift.” We scanned it for codes and found it had P0733, “gear-ratio error,” and when we test-drove it we noticed a slip in third gear. Let me use the following example to illustrate this point.Ī 2005 Hyundai Elantra with an F4A42 transmission came to our shop. So when we change those tolerances, we have to inform the TCM that a particular repair was done or it can make our job more difficult. This function is what we have to take into consideration when we rebuild the transmission or do any repairs to its internal hydraulic system.Īs a clutch wears the TCM adapts that particular gear. Part of the function of adaptation is to allow the transmission control module (TCM) to compensate for the gradual wear of clutches and bands and for internal hydraulic leaks resulting from use.
More and more car manufacturers are making use of this function to keep their transmissions shifting like new as they wear. Shift adaptations are something we have to deal with in the transmission industry.
0 kommentar(er)
