bluejohndeere

after reading a thread on here about check engine bulbs being removed i checked mine this morning and found the bulb missing ,

i replaced it and did a check, i got 22, 23, 24 (knock sensor, maf,idle control)
22Knock Sensor23Mass Air Flow Sensor Circuit24Idle Control System Malfunction
could someone explain what these mean? im guessing they have failed ??

do i just replace the knock sensor and maf and clean icv ??


many thanks bjd

myblackwrx

iTrader: (1)

Reset the ecu first to see if they go or stay.

The problem could just be one sensor but will affect the others and bring up their error codes.

joey_turbo

iTrader: (26)

Also supply some information on what car/year and mods you have.

bluejohndeere

95 wrx import induction kit and backbox.

will leave it to reset whilst i have lunch. many thanks

bluejohndeere

ok i reset the ecu and got the all clear code, i then went for a short drive within 2 minutes the check engine light flashed up. i stopped and checked and got 22.

so do i just change the knock sensor ?? or is its subarus special way of telling me i need a maf ??

Splitpin

Probably. Are you any good with a multimeter?

bluejohndeere

average lol, test the resistance between the two pins maybe ?? any ideas what it should read ?

Splitpin

There are only two direct causes for the code 22 error. One is the sensor itself failing, the other is an open or short circuit in the cabling between sensor and the ECU.

I don't, off top of head, know what the impedance for the early classic sensors should be - if you have a click of the search you'll probably find out. The later classics should be 555Kohm +-5%, to give you a guide. May be that the early ones are the same, I seem to recall they're slightly different.

The early sensors only have a single "pin" so you test the impedance with one of your meter wires to the signal pin, and the other to the metal base of the sensor body. If it comes up open circuit, clearly, it's knackered. If it produces a resistance, as above you'll need to double-check what to expect.

The other thing you could then check is the continuity between the connector the sensor plugs into under the bonnet, and its other end at the ECU. Slipstream_UK's manuals post will get you to a pin-out list for your ECU.

Although, all that said, first thing to do if you're going to take the sensor off and check it, would be a physical exam. If it looks knackered - especially if the plastic body is cracked, assume that it is and go from there.

Make sure you pay attention to some of the other replacement threads on here too as regards tightening torque. Relatively easy to break them by overtightening.

bluejohndeere

yep sensor looked fine but tested it and she was fecked, so popped down the road to grade a.

all sorted shes pulling so well even spins the wheels in third when it comes on boost


thanks for the advice, another happy customer BJD

Splitpin

Nicely done! Worth resetting your ECU, if you haven't already done it. If you've got a KC RAM map built on a duff sensor it's worth cleaning it out and starting again.