Need info on OBD II Codes

My 97 Isuzu Rodeo has the following codes that come up.


P0101 - Mass or Volume Circuit Range Performance Problem.

P0401 - Exhaust Gas Recirculation Flow Insufficient Detected.



From what I've been able to determine so far, that this has something to do with the Air intake and Exhaust/Emissions, but I've not been able to track down any specific parts that need replacing.


Any assistance on this issue would be greatly appreciated.

P0101 - Mass or Volume Circuit Range Performance Problem.


It's referring to the circuit that measures the mass or volume of air flowing into the engine. Check the MAF (mass air flow) sensor, if your car has one.


P0401 - Exhaust Gas Recirculation Flow Insufficient Detected.


EGR Flow Insufficient - your EGR valve isn't letting enough exhaust into the intake system, or the flow is obstructed somewhere. Check the following:

Control input to EGR valve
EGR valve response to input (does it open?)
Unobstructed flow path (no carbon buildup) to and from valve

always take care of the lower numbered code first.