What do I need to check/replace?

[IronMonkeyL255]

I need to get my car running 100%. I pulled my codes and here's what I got:


22 - knock sensor; Abnormal voltage produced in knock sensor monitor circuit

31 - throttle sensor; Abnormal voltage input entered from throttle sensor

49 - air flow sensor; Use of improper air flow sensor


My car seems to run fine. No irregular smells or smoke at the exhaust. The temps seem to stay in an acceptable range. No noticable abnormalities while driving.

Just about the only thing I notice is that I get REALLY bad gas milage (about 170-180 miles to a tank). I used to get over 200 miles to a tank.

What do I need to check for these? How do I check them? I have a multimeter, but not much experience using it.

Could any of these codes be causing the others? About how much would it cost to replace these sensors?

[Legacy777]

Do you get a check engine light? Or did you just happen to get the codes when checking.

They may be old codes. First thing I'd suggest is clear the codes, and maybe trying to use D-check mode.

Check the codes again, and see what comes back.

[IronMonkeyL255]

I reset the computer not too long ago, so they aren't that old.

I checked them before I reset it last time, and a few showed back up. I know the MAF code was there before, and I think the TPS code was there as well.

I may try resetting it again and try d-check mode later this week.

So basically, it is telling me that my MAF sensor, my TPS sensor and my knock sensor are all borked...?

[IronMonkeyL255]

Oh, yeah. It isn't throwing a CEL. Those were stored.

[Legacy777]

You do have the silver MAF on there correct?

if you do, I'd say the MAF might have issues, wiring might be bad, or ECU might be on the fritz.

[professor]

check your alternator...bad voltage input to the ecu means faulty output to the sensors, which then return out-of-bounds voltage and it throws a bunch of codes all at once

[IronMonkeyL255]

I have the silver MAF, correct.