hi guys, i was testing the voltage at the ecu for the intake air thermosensor and injectors and such. my results were higher voltages than spec.

the intake air thermosensor, injectors, and a couple other things read 14V at idle.

what could be the cause of this? my cars running like @ss right now, so is my ecu dead?

thanks!

 

Probable cause is a healthy alternator...

 

Test the resistance of each ECU ground wire to ground.

Also check pin 2I to see if it is holding steady at 5V.

 

will check thanks! i'll check the cars grounds as well.

 

Like the man said, there is nothig wrong with the 14volt figure at the injectors. It's basically battery voltage and if the alternator is a pumpin out juice then you'll see what the alternator is putting out.

The intake air thermosensor is whacky. It should be b/t 2 to 3volts. So that is way wrong.

So......you are reading the outputs with the connectors installed on the ECU, right? Back probing them, right???

You know that the plugs are *labled* by looking at the side of the plug that has the wires going into the plug, right? YOu count from right to left, starting from the top right.

You should not be getting 14v at the pin 2K. You are looking at the pinout for a series five car and not a series four, right?

 

yes it's a S5 and it is pin 2K. i am probing the outputs from the back as per the fsm. Is the problem in the wiring harness then?

 

the AFM itself checks out fine by the way

 

Nobody listens to me anyways....

 

Its really, really odd that you see 12volts. When I get a chance I'll look at a schematic. I was sure that there was but approx 5v reference going to the thing so I would not think you could possibly see 12v on pin 2K. I have no manual etc with me right now. Later I'll look.

Name the other pins that are waaaay off. Don't list those that should have approx 12v and you see 14. Just list those that should have b/t 1 and 5 volts but have a really high reading.

What's the number written on your ECU/?????? as in N333 etc (just an example, I'm not sure what yours should be right now).

 

i'm sorry

 

i have a n350 ecu. the only one thats way off is 2K. i haven't tested some things like mileage sensor, headlight switch and such. i'm sure it did read as 14V though, i even tested it 3 times.

i'm not near my car for the week, but this weekend i could take a pic.

 

Thats okay, my therapist told me its because I am not assertive enough... So I am going to start posting in all caps..
IS YOUR CEL ON? HAVE YOU TRIED TO PULL CODES?

 

no it isn't on, it doesn't come one when the key is in the on position either. no codes, already checked.

 

Have you done this?

What was the voltage you read at 2I?

 

damnit i didn't cheack that one>< i'll have to wait till the weekend i guess. i'm trying to get another ecu, but i have a feeling that i don't need it anyways.

 

The 12V listed in the spec is for when the ignition's on but the engine's not running. As soon as the engine's running, the alternator will push that up to 14V, so that's perfectly normal.

The AFM air thermosensor (pin 2K) should read 2-3V @ 68degF ambient temp. There are two possible reasons for reading 14V on that pin. Either the thermosensor has internally short-circuited, or you're measuring the wrong pin (easy to do). Check it at the AFM itself (FSM page F1-52) to confirm if the thermosensor's okay or not. I would think a short circuit would cause the CEL to come on, but you never know.
You need to elaborate on "running like ***". There are hundreds of possible reasons, and the ECU is one of the less likely ones.

 

From what I understand:

If it was short circuited is would read 0 volts. If it was open circuited it should read 5 volts (assuming the S5 ECU is internally similar to the S4).

For that line to read 12 volts, his ECU's 5V supply (exposed on connector pin 2I) is shot, or his ECU is not connected properly.

 

running like *** is about as technical as i can get! it's got nast hesitation throughout the powerband.

i checked afm itself and looked for cracks and such, and it was perfectly fine.

i checked like 3 times to see if i had the right pin and i got the same reading every time, so i'm pretty sure it's reading at 14v.

trying to get a new ecu, so we'll see what happens! thanks for the help guys

 

It might be worth your time to check everything else BEFORE hooking up another ECU to your car.

If faulty wiring nuked your ECU once, how do you know it's not going to do it again?

 

yeah i see that, but i would so dread rewiring everything... and if the wiring was bad i'd consider just parting the car out

 

Oops, my bad. I forgot that was 5V.

I don't mean a visual check, I mean the electrical check the FSM describes. Basically you check the resistance of the thermosensor.

 

oh yeah forgot to mention that i did check the resistance from the e2 terminal to the other ones (forget which ones off hand) and they were all within spec. thanks again

 

I think THELOUDROOM is suggesting its worth the time to ohm out the wires from the AFM to the ECU one wire at a time to make sure that they are going to the pins they should be going to. Also check for a ground to each wire one at a time with both the ECU and AFM plugs disconnected.

Most likely the 5v ref voltage is not kaput if you have checked other things like the boost/pressure sensor or air intake temp sensor on the intake manifold.

12v is just plain odd. I played with a ECU once that had its ref voltage kaput and it showed some off the wall figure like 1.5 volts on(I think) pin 2A of a series four. If the reference voltage goes **** up it's my opinion a car will not start at all. It seems to be tied in with the workings of the ignitors/coils etc. All gobbly gook to me.

 

i'll try checking all the wiring and the pressure sensor then. try putting in some grounds too. the car has had a difficult time cranking up since i stuck a new battery in and my friend messed with the timing.

anyways, thanks for the help!

 

Didnt I say this like 8 or 10 posts ago?