diagnose codes 157 and 159

[pejohnson]

I have a 95 MTX that has the 80mm Pro-M (Professional Flow Technologies) MAF sensor and cone kit. I have had the car for about 3 years. Recently I have been getting a check engine light that comes on intermittently. Mainly after the car is warmed up and during deceleration the check engine light will flash for about 3 seconds. Not every time, just sometimes. I checked the codes tonight and they were:

157 MAF circuit below minimum voltage
159 MAF out of self-test range

I have cleaned the MAF sensor several times with MAF cleaner and that didn't help.

My thoughts are I need to send my MAF sensor into Professional Flow Technologies and have them either re-calibrate the sensor or replace it.

Does this seem like the right approach to solving the problem or is something else I should check before replacing the MAF sensor?

PS - The previous owner installed the MAF sensor so I don't know how old it is. I would assume over 10 years old probably more.

 

[rubydist]

its possible that the mafs is bad. with that code, it is more likely to be a wiring or connector issue, in my experience.

I would start with checking all the wiring and connectors in that circuit.

 

[luigisho]

Do you have, or know someone who would swap their oem MAF on the car? That's the quickest way to rule it in or out.

 

[pejohnson]

I don't know anyone near me nor do I have an extra MAF sensor to check. I'm not real good with wiring diagrams so checking it probably isn't an option for me to do. I unplugged the MAF sensor while the car was running and the light came on immediately however the car seemed to idle fine. Not sure what that means? I guess either I will have to take it a shop and have them check out the wiring or roll the dice and get the MAF sensor re-calibrated or replaced.

 

[kevinspann]

Usually unplugging it and having it run better is a sign of a bad/dirty maf.

 

[rubydist]

but unplugging it and having it run better does not rule out a bad connector either...

 

[pejohnson]

I was working on the car today and noticed the Pro-M 80mm filter says not to oil. Well guess what I put oil on it probably about 2 years ago. I wonder if that might have messed the MAF sensor up. I've cleaned it several times but doesn't seem to help. Also curious as to how you are to clean these Pro-M filters?

 

[93markVIII]

yeah, oiled filters and mass air sensors don't mix. you need to clean the mass air sensor wire.
if that didn't help, you are back to just a bad sensor, or bad wiring.

 

[SHOdded]

Be sure to use a cleaner specifically made for MAFs, that's your best bet. Don't touch the sensor wire.

 

[pejohnson]

Okay guys I need some more advice. I went ahead and bought a new Pro-M MAF sensor and filter, installed them and still have the same issue. The check engine light will come on sometimes, typically just a few seconds and then it goes out. Typically it will come on during deceleration, not sure why. The same codes come up. I'm not sure what to do now.

 

[SHOdded]

Time to check the wiring and the connectors in the MAF circuit, like rubydist mentioned previously. Can you snap a few pics to help us see what might be going on in your case?