HAZE

this is related to another thread about some codes i'm troubleshooting but it has only to do with the maf.

getting a 102, 443, 449 code.

logged for maf activity and got 0

getting iat readings that seem correct

figured maf is shot but thought i'd try to check it.

with the clip side up i probed all the sockets, here's what i got starting from the left side w/ the wire color. this was a key on maf unplugged , motor not running test.

yellow- 5v

pink- 11v

black/white- 0v

light brown- 5v

black-0v

tested 0v volts to ground, have continuity

double checked readings using plug ground instead of vehicle ground, same results.

have 12.6 v at the battery.

if what i've read is correct, the yellow should be the signal wire and shouldn't have voltage.

the pink should have battery voltage

the tan should be the iat power wire and have 5v

before i tear into the harness and the pcm i wanted someone to verify that something isn't right here

truck is 02 chevy 1500hd 4x4 with 6.0, whipple compressor, 8.1 inj's, nelson tune, no whipple electronics

thanks for any advice

HAZE

been searching for maf testing procedures, found one related to a pontiac that stated the signal wire voltage is a 5v reference circuit. i'm taking that to mean that it should have 5'v at the plug.

hopefully that means a don't have a harness short or pcm issue.

i didn't want to get a new maf and fry it with an electrical issue.

guess i'll either try to bench test the maf or back probe it when runnig to see if i get a resistance reading.

KySilverado

iTrader: (7)

PM me your email addy and I'll send you the service info for those codes.

HAZE

thanks for the diagnostic sheets, appreciate it.

didn't have time to do much but i read over them, some of the tests i can't do because i dont' have bidirectional control on efi live [used edit for tuning and efi for logging]

any suggestions which to start with ? meaning, if associated, which is more likely to cause the other to code ?

according to my logs i am getting no maf activity yet i have voltage and iat function.

i'll do the best i can with what i have, thanks again

KySilverado

iTrader: (7)

Only code 102 is MAF related. Codes 443 and 449 are EVAP codes. I would follow procedure for checking the 102 code.

I wouldn't be using EFI to diagnose. A multimeter under the hood will go a long way.

HAZE

yeah i can handle that part, actually thought i had to soe extent , least with testing for voltage at the plug.

i think the part of the solenoid test involved commanding the sensor on and off, no big deal on that one, if in doubt it's only $36 to just change it out. do you know off hand if that solonoid should rapidly click with constant voltage ? or is it varying voltage that makes it cycle ?

HAZE

quick update,

stated checking wiring, been so long it took awhile to get my bearings. seems i never put the wiring harness back to stock and was using the pigtail adaptor that is supposed to return the wiring to stock config. one of the pigtail wires was worn through to wire but it was rubbing on plastic so ........

no voltage at maf sensor power wire now, have reference voltage and iat but no maf, ruh roh.

hopefully didn't fry part of the pcm, going to tear the harness apart and put it back the way it should be and test the maf pin at the pcm before i do it, fingers crossed.

HAZE

got the pcm wiring back to stock, didn't cure anything.

i have voltage at the maf, just wasn't getting the probe in far enough.

did all the tests i can on the diagnostic sheets with a multimeter, don't have a signal generator or a bidirectional scan tool so i guess i either go get one, take it in or throw more parts at it.

guess a new solenoid is on the menu for tomorrow ...... very annoying problem here. everything so far checks out ok, the new maf didn't help, if the new solenoid doesn't i'm not sure where to go ....... ignition relay ?

guess i'll have to ask the dealer mech what he thinks ..............

HAZE

replaced the purge solenoid today, it helped ..... sort of.

cleared the codes, idled it for awhile, no codes or pending after 5 minutes [they were setting almost immediately]

took it for a drive, after about 5 minutes it set same three pending codes, went home, after idling for 10 minutes while i looked for vacuum leaks it set the codes again.

logged again and it shows maf activity [2300+ hz while idling]

idle is not as even as normal and it actually died once [why i was looking for vacuum leaks]

the only thing i havn't replaced that's related to the codes is the vent valve solenoid.

any guess's ? egr ? iac ? something i am completely missing ? since the purge solenoid seemed to have an effect, direction to go from here ?

just thought of something, i wonder if it's possible my blower bypass valve is bleeding air in to the circuit ? still works [have boost on throttle and vacuum off] but maybe .........


someone out there has to be a lot better at this than i am

HAZE

ok figured it out, i hate when people don't come back and say what the solution was.

when i said i wasn't getting power to the maf, i thought it was me not probing right, turns out i wasn't crazy and shouldn't have doubted myself.

after doing all the tests i could, and all of them pointing to the sensors failing, turns out it was ..............

a faulty ign relay

thests all said check the fuse eng 1 but didn't mention that the relay right next to it gets the power next. the relay was working intermittently and of course was delivering power when i tested. when the load of the three sensors was on the circuit, the relay couldn't handle the load and would deliver low or no voltage. i only realized this after i had replaced the sensors and the relay stuck open and i had no voltage.

a friend of a friend who's been a diagnostic tech suggested it could be an ignition switch and sent me a full wiring diagram, i checked the wiring and eliminated that but noticed that the circuit had a relay, a quick tap on it confirmed the problem by delivering voltage at the sensor. so to make a long story even longer .......... a $12 relay was causing all this %&$&$((* .........

i don't know for a fact that one of the sensors wasn't faulty or shorted and cuased the relay failure but, if you get these codes that would be the first thing i would suggest checking. it's the square relay right next to the eng 1 fuse. this relay powers the maf, purge solenoid, vent solenoid and if you have two tanks it powers the secondary pump relay.

anyway, thanks for the help, diagnostic sheets and comments. hope this helps save someone from buying three new sensors

also thanks to chris who's now at honda of oxnard who put me on track to this solution. great guy and knows his stuff.