Anyone know how to troubleshoot.....

A couple of weeks ago, the SES light on my '96 came on....

Car runs fine but the code I get from the diagnostic reader is a mass airflow sensor related issue. Before I pop for a new one I'd like to try checking the three terminals for proper resistance. I get 6500 ohms between two of them.

Any of you wizards out there know what the numbers should be??

No I don't, but I do know one trick with MAF's...if you thump it while the motor idles warmed up and it causes the motor to react by missing or cutting back, it's bad.

This only works if the problem is an bad connection in the sensor grid or board...used to be a common problem on those...first thing I'd do if one came in with a MAF code or intermittant stalling or hesitation...

pink = incoming voltage
blk/wht = ground
yellow = output signal

But I don't think resistance is a valid check for that sensor, I think it's output is a frequency wave, varying with the air flow ... better off checking it against a frequency counter or oscilloscope or scan tool, than for resistance with an ohmmeter, whether it has resistance or not doesnt mean it's going to work correctly. Neither checking resistance nor voltage would be sufficient to determine if it's working correctly or not.



if your multimeter doesn't have a frequency counter, then you can get one from radio shack for $50, there are a couple to choose from at that price. Check yellow with either ground or +



and definitely try tapping the sensor while idling.. can do that without any tools.



also.. jsut because the error code mentions MAF, doesnt mean the maf is bad, it only means the PCM is 'expecting' the MAF to return a value within a certain range.. but it's returning a value outside that range.

could be something wrong elsewhere, that confuses the PCM into thinking the engine should be getting more/less air than what is actually going in the engine, the MAF is simply reporting the ACTUAL air going in, and the PCM is saying "wait! that's the wrong amount of air! OOOO MAF ERROR!!!"


think of it as an equation


the PCM has one equation:

(2xMAF / TPS) = [value in lookup table, based on O2 reading]

Now if 2xMAF / TPS doesn't match what's on the table, it throws a code, which says MAF. However if something has 'tricked' the PCM, like a bad O2 sensor to look at the wrong table entry, then the reason it threw the code was because it looked up the wrong table entry... not because the MAF is bad. Could be bad TPS, O2, or any combination of things.



or you could have a vacuum leak, allowing more air to get past the throttle body without being measured. The MAF would continually report less airflow than the actual airflow



and for next time

list engine size
trouble code

at the minimum....




ps: hope you frequent posters (jeffco, max, richtazz, and all) buy a dodge ram one day... I just bought a ram and noticed those forums don't have as many helpful people in there as this one :)

A couple of weeks ago, the SES light on my '96 came on....

Car runs fine but the code I get from the diagnostic reader is a mass airflow sensor related issue. Before I pop for a new one I'd like to try checking the three terminals for proper resistance. I get 6500 ohms between two of them.

Any of you wizards out there know what the numbers should be??

do you have check valves and air pump on this engine? check for air duct to be secure and that you have no large vacuum leaks as this will cause this to occur, as extra air is bypassing the maf. also if maf is dirty sometimes water/oilsK&N air filter can get on maf wires and this will create problem if dirty use crc maf cleaner only, never touch small maf wires ok to spray cleaner on them......because it runs ok maf is probably good just out of predetermined range that pcm expects to see......

Lots of food for thought expressed above. I'll track down the opportunities for a vacuum leak and go from there. It's a 3.1 engine, and the actual code numbers are unknown.

I'll also give it a rap to see if anything changes.

The guy that took the reading didn't pass the code on to me. The good news is that the car runs fine (except some stumbling on cold start up, which goes away quickly)

Thanks for the input.

something else to check, can cause a sort of vacuum leak, the EGR valve. seen those where the pintle is loose or sticking open. should set a code for that too, but also seen it where it doesn't. all the advice given above is excellent, just one more thing to check that i didn't see listed.