The service engine soon light came on and I have my smog station guy read out the fault code. It is P0734 - Gear 4 incorrect ratio. Does anybody know what it means. He cleared the fault and the light is now off. I don't know if it will stay off as I have just drove the 15 miles to bring the car home.
Mine is a 1999 4.6HSE with 60K miles.
Thanks in advance for any info.

 

How often do you clean/replace your air filter?
Are you using a K&N air filter?
The 734 is one of 3 codes that can come up when your MAF is failing.
If it comes back get the codes read, see if there are any other codes and get back to us.

 

Mike,

Thanks for the reply. I am using the stock filter that was changed 30K miles ago. I have searched the forum for P0734 and noticed all other members has several codes that came up with the 734. I got only the P0734 code and no others. Yes I understand the 734 did not come back for others after they change the MAF. What I don't understand is what has the MAF got to do with the 4th gear ?

 

the transmission needs to know how much load is on the engine, when it sees a large load, it wont engage over drive, 4th gear. it gets the engine load value from the ecm which calculates it based off of your mass air flow reading. so if your mafs fails and reads high, your tranny always thinks youre on the gas and will never shift into 4th.

 

Dave,

Thanks for the clear explanation. Do you think the Mass Air Flow sensor cleaner on the market will make the MAF last a little bit longer ?

Thanks,
Steve

 

Do not you any MAF cleaner on that Bosch MAF, more harm then good can come from it. There are other codes that can lead to replacing a MAF, a 733 for 3rd. gear and most of the 170 thru 175 codes. Besides, until you see other codes showing up, you really shouldn't just start throwing parts at it.
Let us know if the code comes back.