[shilda]

The P0734 fault code started as soon as I installed a 2" lift, 265/75R16 tires, , and an ARB front bumper with winch. I owned the vehicle for one year without the fault code, now it appears about once a week. Any ideas?

 

[gurunutkins]

It may be that your front tires are deforming more than the back tires and the slip between the front and rear is not exactly the same triggering the fault - otherwise you may have a transmission shift problem.

here is the chapter and verse from the good book

P0734 LAND-ROVER
Gear 4 Incorrect Ratio
Symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
- Incorrect transmission shifting
Possible causes
- Low transmission fluid level
- Dirty transmission fluid
- Shift solenoids
- Transmission mechanical problems
- Transmission hydraulic control circuit
Tech notes
Start by inspecting the transmission fluid level and condition, and change fluid if necessary.
Description
This diagnosis monitors actual gear position by checking the torque converter slip ratio calculated by
Transmission Control Module (TCM) as follows:Torque converter slip ratio = A x C/BA: Output shaft
revolution signal from revolution sensorB: Engine speed signal from Engine Control Module (ECM)
C: Gear ratio determined as gear position which TCM supposesIf the actual gear position is higher
than the position (4th) supposed by TCM, the slip ratio will be more than normal. In case the ratio
exceeds the specified value, TCM judges this diagnosis malfunction.
When is the code detected?
P0734 is detected when A/T cannot be shifted to the 4th gear position even if electrical circuit is
good.

Cheers
Barri

 

[belew]

I would strongly suspect the code being a failed or failing MAF. With the correlation to the timing of the other modifications being coincidental.

The standard OBD-II code P0734 for Gear 4 Incorrect Ratio is typically bogus on the Disco II. Usually triggered by a failed MAF.