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SUPRYZE, Technician/Shop Foreman
Category: Car
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Experience:  GM & Saab Certified, ASE Master Technician
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99 callaway Range Rover has Diagnostic Trouble transmission

Resolved Question:

My '99 Callaway Range Rover has Diagnostic Trouble Code: P01178 (T) AMFR correction at its masximum positive value... Would you translate this for me?
What does AMFR mean. I think I need to change my Mass AirFlow Sensor. Could a bad MAFS affect my transmission? It is shifting hard from 3rd to Drive. All else is OK. Thanks for any help here! Paul
Submitted: 7 years ago.
Category: Car
Expert:  SUPRYZE replied 7 years ago.

Hello! AMFR stands for Air Mass Flow Rate. Basically, the code indicates that the computer is having to add/subrtract fuel as compared to what the Mass Air Flow meter says is coming in. This could be caused by vacuum leaks (from the intake gaskets or vacuum lines) or a faulty Mass Air Flow meter.

When we get problems like this in, we hook a smoke machine up to the intake, to help pinpoint vacuum leaks (if any). If you have a suitable scantool to monitor live data, you can spray around the intake manifold and vacuum lines/intake duct work with carb cleaner and watch for changes in the data. Sudden spikes in the adaptation values or O2 sensors indicate a leak.


If all that checks out OK, then you may have a faulty MAF sensor. The MAF sensor is also used as a load input, to help with transmission shifting, so a faulty MAF sensor could cause transmission issues, but without actually looking at the vehicle, these are only "possible" causes.



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