My 00 Disco II failed state inspection due to fault codes P0174 - Right Bank Lean & P0734 - Gear 4 Incorrect Ratio. I took it in for diagnosis, thinking the first one was due to either a bad O2 sensor or Cat. The mechanic performed diagnostics & drove it for about 30 mi & found no faults or problems with the sensors. He found that the plug on the Mass Air Flow Sensor was loose & said that this was the source of the fault codes.

I took it back for reinspection this morning and it failed again, due to P0734. It had about 60mi on it since the computer reset, so I thought this might still be in memory as the check engine light had not turned on. I decided to drive it for another 60mi before taking it back for re-inspection, lo & behold the check engine light is on after about 20 mi.

I saw a previous post stating that these codes are due to a faulty Mass Air Flow Sensor, but did not see any resolution.

Has anyone had experience with a P0734 fault code, what was the cause & how did you resolve it?

Thanks, Rich

 

follow this link and try to clean your MAF. if you can get some eletrical cleaner it would be better that carb cleaner but carb cleaner works.
Also here is the service info related to that code below.

DTC P0734
Gear ratio monitoring (4th gear).

Possible causes by suggested order of priority:


Output shaft signal not to specification.
Engine management ECM faults present.
Open circuit C243/E (K) to C193/42 (R).
Open circuit C243/F (B) to C193/14 (B).
Shaft speed electrical interference.
connectors C243,EAT C193 .
Open circuit shaft speed sensorC193/14 (B) to C193/42 (R).
Shaft speed sensor fault.
Torque converter mechanical fault.
Gearbox mechanical fault.
Output Shaft Signal Not To Specification.


If using TestBook, the display shows the output shaft speed as measured by the transmission ECU and the engine speed as measured by the engine management ECM.
(If TestBook not available, use Live Data reading function on Scan Tool. [See Scan Tool manufacturers handbook for detailed instruction]). CHECK THE FOLLOWING:
Check the gearbox specifications and ensure that the ratio of the engine speed against output shaft speed while in 4th gear is correct (drive vehicle on rolling road or road test).
At constant road speed with no gear changes both TestBook readings should be stable.
The two readings should also maintain the same ratio so long as no gear changes take place.
If the output shaft signal is unstable there may be a problem with the output shaft sensor circuit.
If the engine speed signal is unstable there may be a problem with the ECM or its sensors.
If the gear ratio is not to specification there may be a problem with the gearbox.
(If TestBook not available, use Live Data reading function on Scan Tool. [See Scan Tool manufacturers handbook for detailed instruction]). POSSIBLE FAULTS
Output shaft sensor fault.
ECM or ECM sensors fault.
Gearbox mechanical fault.
Engine Management ECM Faults Present.
CHECK THE FOLLOWING:


Read ECM fault codes and check if any crankshaft sensor, engine speed, engine load/airflow or engine torque measurement faults are set.
Any faults present should be rectified. POSSIBLE FAULTS
Faults set in ECM.
Open Circuit C243/E (K) To C193/42 (R).
CONNECTOR


Check for connector not correctly latched, backed out pins, damaged pins, corroded pins.
Open Circuit C243/F (B) To C193/14 (B).
OPEN_CIRCUIT


Check resistance > 1M Ohm
Shaft Speed Electrical Interference.
OPEN_CIRCUIT


Check resistance > 1M Ohm
Connectors C243,EAT C193.
OPEN_CIRCUIT


Check resistance > 1M Ohm
Open Circuit Shaft Speed SensorC193/14 (B) To C193/42 (R).


Use Live Data reading to display the output shaft speed as measured by the transmission ECU. CHECK THE FOLLOWING:
With the engine running and the position switch in 'P' the shaft speed should measure 0 RPM.
If the reading is not 0 RPM then there may be a problem with electrical interference.
Check the connections to the screen around the output shaft sensor wiring. POSSIBLE FAULTS
Faulty output shaft sensor wiring.
Faulty output shaft sensor.
Shaft Speed Sensor Fault.


Use Live Data reading to display the output shaft speed as measured by the transmission ECU. CHECK THE FOLLOWING:
Monitor the road speed (from the vehicle speedometer) and the output shaft speed while driving on the road or on a rolling road.
The two readings should maintain the same ratio. If one reading doubles so should the other reading.
If the readings do not maintain a fixed ratio the output shaft sensor may be faulty. POSSIBLE FAULTS
Faulty output shaft sensor
Torque Converter Mechanical Fault.


Use Live Data reading to display the output shaft speed as measured by the transmission ECU. CHECK THE FOLLOWING:
Monitor the road speed (from the vehicle speedometer) and the output shaft speed while driving on the road or on a rolling road.
The two readings should maintain the same ratio. If one reading doubles so should the other reading.
If the readings maintain a fixed ratio the torque converter may be faulty. POSSIBLE FAULTS
Transmission torque converter mechanical fault.
Gearbox Mechanical Fault.
CHECK THE FOLLOWING:


Ensure none of the electrical faults described in this section of the diagnostic are present.
Road test the vehicle. Ensure all gears are engaged during testing.
If the gearbox and vehicle behave abnormally there may be a mechanical problem with the gearbox. POSSIBLE FAULTS
Gearbox mechanical fault.

 

Thanks for the help. It ended up being a Mass Air Flow Sensor. Put a new one in and it passed.
Cheers,Richo

 

good work, did any of my info help?

 

It sure helped me... THANKS! You r the man!

 

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