Land Rover Repair: Check engine light - gear ratio, mass air sensor, obd scanner

Question
Thank you!  I replaced the mass air sensor yesterday after reading some other posts about the 2 system lean codes I was getting.  The car drives so much better, but now have a new code p0154, no activity?  Thank you again.

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-----Question-----
I have a 00 Discovery II with 90k on her.  Her check engine light came on, and using an OBD scanner, i got the codes for 3 and 4th gear ratio being incorrect.  Any ideas?  i noticed a while ago, she did not want to kick into 4th driving down the road, till i came to a complete stop.  Thanks!

-----Answer-----
Those codes could point to a problem in the transmission, but they can also point to a failed mass air sensor on the engine.

Answer
0154 means there is no activity from one of your o2 sensors.  That could be because your sensor has failed, or it could be because the is a problem with the engine that's making it stick rich or lean - a vacuum leak or a leaky fuel injector, for example.

The next step would be diagnosis of the sensor with a scope and an exhaust gas analyser.

There's an article on my web site about o2 sensor diagnosis, www.robisonservice.com > service > land rover > articles