Hyundai Repair: 1999 Hyundai Accent Codes, vehicle speed sensor, transmission control module tcm

Question
I have a 1999 Hyundai Accent with 149K and a 1.5 four cyl. engine;the engine runs well and still gets great MPG. Recently the check engine light came on and I went straight to Auto Zone to have the codes pulled(in the past by the time I got to Auto Zone, the light had gone out and they could not pull the code).One other piece of info. that may be important;the day before the codes appeared I noted an issue with the transmission seeming to downshift out of overdrive(but the following day when I went to Auto Zone it drove fine;the Transmission was rebuilt about a year ago by a reputable shop). The codes that were pulled wee as follows:
1. P0733
2. P0722
3. P0734
4. P1613

Hope I didn't give you too much info. to try to deal with.

Thanks for your time

Rick

Answer
The information is very good, Rick.  Chances are high that you have a minor issue.

P0722 indicates that the output speed sensor is not reading correctly.  This is typically an intermittent issue within the speed sensor itself, but sometimes an issue with a poor connection in the electrical connector for the sensors.  I'd recommend replacing the pulse generators (Hyundai's name for the input and output speed sensors, which come bundled together), and twisting slightly with a pair of needlenose pliers each of the male pins in the connector for the new pulse generators.  This will help insure good contact in the connector.

P0733/P0734 basically indicate the transmission is slipping in 3rd/4th gear, but since we already know there's a problem with the output speed sensor signal, you shouldn't attempt any diagnosis or repair regarding these codes unless they return after the P0722 code is repaired.  The transmission control module (TCM) uses the signals from the pulse generators and the vehicle speed sensor to determine whether the transmission is slipping.  In this case, it's most likely that your transmission isn't actually slipping, but that the P0733/P0734 codes are erroneous due to the faulty pulse generator.

P1613 indicates that the voltage in the MIL request line is too high.  The MIL request line is a dedicated wire running between the TCM and engine control module (ECM) on which the TCM requests the ECM turn on the check engine lamp.  If your car is produced prior to 12/4/98, Technical Service Bulletin 99-40-004 indicates you should replace the TCM with updated part number 95440-22691.  Even if produced later, the problem is still most likely within the TCM.  Since this is an expensive repair, you might simply repair the P0722 code, clear all, and see whether the P1613 returns, and if so, how long it takes to do so.  My experience is that this diagnostic trouble code (DTC) occurs very intermittently.