I recently bought a 2000 Discovery and apparently the used dealership disconnected the check engine light. I used my scan tool and found this code P0734, which means Gear 4 incorrect ratio. I noticed the vehicle doesn't shift to 4th gear. I have a shop service manual, read that I could do a stall test, pressing the brake and parking brake and pressing the accelator to see the RPM. And the RPM reached 2300 and that's ok according to the service manual. It also has the codes:
*P0174 system too lean (bank 2)
*P0150 O2 sensor circuit malfunction (bank 2 sensor 1)
*p1174 Lambda control adaption fault bank 2.Last occurrence - maximum signal

My questions are:

1. does someone know what is o2 sensor 1 is? Which of the 4?'
2. if the system is too lean may the computer prevent the shift to 4th gear to prevent an backfire?

Normally I fix my own cars, but the Land Rover is compeltely new to me.
Any help/ideas would be greatly appreciated.

 

If your Discovery has the Bosch engine management, then this is not possible. Shift patterns are not affected by lean conditions.

Are you noticing this lack of shifting in a cold climate? When cold (I forget what minimum Temp), the automatic tranny's computer will purposely not allow the torque converter to fully lock, allowing slippage until the ATF has reached a specific temperature. You may notice your rpm's are higher at a higher velocity, like on the highway. This will drop in two stages until the temperature is in acceptable range.

When I first got my Discovery, I thought I had a 4th gear shifting issue until I found out how it works.
Hope that helps.

Daniel

 

Thanks Daniel, i'm confused too about the tranny, the rpm's drop only a little bit on third but i don't feel a shift, also today i replaced the sparkplugs, the ones it had were gaped incorrectly (42) instead of (32). That fixed the lean condition code.

I tested and pulled codes P0150 ( O2 sensor circuit malfunction bank 2, sensor 1)
and P0734 (gear 4 incorrect ratio)

I would like if someone can tell me the RPM their disco do at 70, 75, 80, 85mph
or a what speed usually shift to 4 gear.



Thanks.

 

https://landroverforums.com/m_6334/m...y_/tm.htm#6334

 

thanks again Daniel, mine is doing 3000 rpm at 60mph and in low range in manual mode doesn't shift to 4, looks like the previous owner replaced the front shaft and the transfer box looks new, the code bar paper sticker still on it, the connectors on the transmission are clean. Please any suggestions/ recomendation is welcome.

 

I changed the O2 sensors and the codes are gone except for the transmission code, i will take the Disco to the mechanic next tuesday, tomorrow i will try to put more ATF, i did unbolt the filler bolt and seems like is not full... that's my last chance before i get bent over by the mechanic