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mralexc
mralexc, ASE Certified Technician
Category: Car
Satisfied Customers: 25
Experience:  ASE certified Master Automotive Technician, Vocational Degree in Advanced Automotive Technology, Nissan dealership training,
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isuzu axiom: 02 isuzu axiom p0101 changed sensor 3 times and

Customer Question

02 isuzu axiom p0101 changed sensor 3 times and not any better.. one wire has 12 volts key on.... the other has a ground... and the third wire has 4.9 volts with key on
Submitted: 1 year ago.
Category: Car
Expert:  mralexc replied 1 year ago.

Hi my name is alex and i am going to try to help,

 

Did you take those readings from a backprobe with the part in place ? and have you tried to clear the dtc with a scan tool ? do you have a scan tool that is able to read other data or just the codes ?

Customer: replied 1 year ago.
Yeah I checked it with my powerbrobe. And I cleared the dtc and it comes back right away. Yeah I can give you whatever readings you would like
Expert:  mralexc replied 1 year ago.
cool ok i see you are a tech so i am sorry for getting back so late i had to eat and get my kid from school. so i apologize .

The square wave you have is normal the 4.9 v is the maximum for the MAF that 4.9v should be at base idle and as the idle goes up the voltage will go down as air goes over heating plate it cools and acts like a coolant temp sensor it is a negative coefficient Thermistor as temperature decreases resistance increases so the MAF signal voltage decreases normal idle voltage should be 4.8-5.0v at WOT the voltage should be roughly 0.5v

if this is what you are getting from the MAF then it is a good part and we need to understand why the computer is having a problem with this.

first check power and ground you said you had 12v how about ground is there allot of resistance, then check the signal wire from the maf to the pcm.

if it happens when you are revving the engine then you need to scope the TPS view it at about 2 ms /div to a 1 sec/ div open to close a couple of times to verify that the TPS is sending a proper signal, look for a dip in the signal voltage. sounds silly but i have seen it happen before and cause a maf code. because the computer reads the maf in comparison to the TPS


if you are idling the engine does the computer read the maf signal to be 4-7 G/sec at idle with the scan tool

and then go WOT you should see 25-40 G/sec does this occur?

Does the ses light come on at idle or are you revving the engine when it occurs ?

have you checked the wiring harness for damage and the connector at the pcm for corrosion or looseness ?

and finally compare your readings with the freeze frame data pay attention to the TPS and MAF reading

let me know what you find, if you find the problem do not forget to rate if not we will go from there
Customer: replied 1 year ago.
okay before i go any further i get a p0300 and a p0152 but those i ignored because they have to do with the maf code.. when im running the car the light flashes signiling the random misfire... also on the live data i only get 1 g/sec and when im with the full throttle the highest it will go is 6 g/sec....
Customer: replied 1 year ago.
Relist: Other.
Taking too long
Expert:  mralexc replied 1 year ago.
same expert would you like me to continue to help i was looking up the other two codes and btw p0152 will not set if there is a maf code
Customer: replied 1 year ago.
sounds good and sorry its cause i would like to solve this issue by today.. and ok when i clear the code it takes maybe 10 seconds for it to come back.. i have 1 g/sec and sometimes even .09 g/sec.. at WOT i barely get 6 g/sec.. now if the car is running it might get 26 g/sec but not always im leaning toward the tps but would like to test it to verify it and not just throw parts at it.. the auto parts closes at 10pm and its 835pm so i have a couple hours
Expert:  mralexc replied 1 year ago.
ok just answer is acting funny i am trying to get into chat mode but its not working

to check the tps you are going to need a scope, if you dont have one available then you might use a dvom to watch the voltage swing
Expert:  mralexc replied 1 year ago.
can you tell which cyl is the missfire?
\
Customer: replied 1 year ago.
ok i have a dvom how shall i check it?
Customer: replied 1 year ago.
yeah i can i have a blue point coil on plug quick probe
Expert:  mralexc replied 1 year ago.
to check the tps you will want to backprobe the signal wire insure that you have a good power and ground to the tps then back probe the signal wire and open and close the throttle and watch the swing you should get .5 to 5 volts if i remember correctly
Customer: replied 1 year ago.
There is 8 wires on the tps connector which ones would I check for ground power and signal?
Customer: replied 1 year ago.
also as i press the gas the butterfly on the throttle body doesnt move
Expert:  mralexc replied 1 year ago.
I am starting to think it is your pcm but i will look up the wiring diagram for the tps it is redundant there are two sensors and the vehicle averages them to give you the open position i is also a redundant check or a bad tps like a failsafe
Customer: replied 1 year ago.
Ok let me know soon please as what you may think it is
Expert:  mralexc replied 1 year ago.
mitchell 1 says to use a scan tool with the ignition on and watch the voltage swing on the scan tool the tps should read about 0.4 volts while closed
Expert:  mralexc replied 1 year ago.
ok you are not reading the maf properly o the pcm there is a missfire which could be because of the maf problem and you have a code for o2 signal being out of range

all three of the diagnostic flow charts say check the pcm grounds and the engine grounds you need to start there the new maf meter is not going to be wrong it works you checked it had proper voltage so the signal wire to the pcm is not being properly read but you cannot fully check the maf without the engine running without a miss which a maf will cause.

ok back to basics are there any vacuum leaks?

and you have fuel and good spark ?
Expert:  mralexc replied 1 year ago.
Are you still there ?
Customer: replied 1 year ago.
hey im sorry but I accidently put loosey goosey a type of wd40 into the throttle boddy while I was lubricating the gears inside the sensor... now the car is backfiring.. any way on how to get it all out before we continue because its not going to run right
Expert:  mralexc replied 1 year ago.
hey buddy you might try some electrical connector cleaner and some maf sensor cleaner spray. you might have to take the throttle body off and the tp sensor and clean it and let it dry. and then pray it didn't get hurt.

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