sint3k

Hey everyone , first time to this forum. Ive done alot of reading on here about the p0221 code however mine seems to be a bit unique. I'm working on a freinds car that he bought. The car he bought is a 2003 Sentra , with a 03 Maxima 3.5 Motor swapped into it. So basicailly the wiring harness , ECU , etc is all 2003 Maxima 3.5. Long story short it appears to be in some type of limp mode where the throttle body does not react at all after the engine has been started.

I checked the ohms reading on the throttle body actuator and it read within specs "between 1-15 ohms". It read 6ish.

I Checked the voltage on both Throttle body sensors "Blue wire & White wire" I tested them at the ECU AND at the throttle body. the Blue wire reads 4.5v "Pedal depressed". and 1.68v "Pedal pressed" the White wire reads "1.6v Depressed and 4.5 pressed. Which are within specs according to the FSM.

I though this might also be a issue with the actual pedal. I tested both sensors and both are within specs as well.

I Did a voltage drop test on the ground wire on the throttle body and noticed its reading over half a volt. So for now i manually connected a seperate ground wire. Once i did this i'm able to open and close the throttle body plate while the key is in the run posistion but engine not running and pressing/depressing the accelerator pedal.

Something else that is weird. When the actual connect is disconnected from the throttle body i probed it for voltage and the white wire "sensor 1" read 5 volts coming from the ECM , Which seems VERY strange. the other sensor "sensor2 blue wire" reads 0 Voltage. I'm pritty sure both of these sensors are fed voltage from the red wire and 5 volts should not be coming FROM the ECU on a sensor wire however ive been wrong before. I know ive included alot of information and will likley be confusing as ive probably left some things out however any help with this would be greatly appriciated . The only code is p0221. Also to add another note , the person who owns the car already changed the MAF thinking it was MAF issue. and also the car will not rev past 1500RPMS , when you push the gas down while its running it does raise the RPMS a little bit but the throttle plate does not move AT all so i dont see how it would be doing this unless it was using the idle air controller "if it has one" anyways

Thanks

Max_5gen

iTrader: (2)

It seems ECU doesn't like the signal from throttle position sensor and you have strange ground problem there as well: 0.5 V difference between sensor ground and ECU ground (if this is what you measured) is way too much, you must have bad ground contact somewhere or some high current circuit shares the ground with the sensor's ground. In both cases ECU will see a lot of noise and won't be able to read the signal correctly. I'd examine very carefully the wiring between ECU and TPS sensor. ECU feeds sensor with 5V (what else- the rest of the car is 12V), I'd also expect sensor to have dedicated ground wire from the ECU which should be isolated from the throttle body ground on the throttle body side to reduce the 'ground noise'. Please do not connect all the grounds on TB side together, this would increase noise in sensor signal from ECU point of view.

sint3k

Really anything over 100mv is to much for a sensor ground. These sensors share the same grounding location as the ECU , Transmission , ACcelerator pedal and a few other things This ground name is "J/C 20" As far as the 5 volts i was referring to is usually the 5 volts is fed from a "reference line" to potentiometer "sensor" and then the results go to the ECM. In this case , 5 volts is coming FROM the ECM "ON" the signal wire "Without the wire even being connected to the Throttle body" Some designes use this method but usually you would see it on both Signal wires , not just on one. But anywho. There is definatly a ground issue. I'm going to check all my other grounds to see if im getting this crazy high voltage on sensor return that should not be there. I'll also do a short to ground and short to power test and isolate the signal wires. Thanks for the help. It would be very helpful if someone could tell me the voltage they have on the Blue and White wire on the connector on the Throttle body "With the connector Unplugged and Key on engine off

Anyways , Thanks!

Max_5gen

iTrader: (2)

ECU has internal +5V source it uses to power sensors (red wires). Take a look at pages EC-29, EC 664, EC658 of 2003 Maxima FSM they show overall circuit diagram as well as wiring of TPS and Accelerator Pedal Position Sensor (APP). It looks like both TPS and APP are simply dual potentiometers with one end connected to +5V ECU output, another- to 'signal grounds' from ECU so the voltage on their sliding contacts should change in the range of 0.4 .. 4.75V relatively to those grounds (FSM has exact range specs for each) while you move them from one end of their scale to another. APP is slightly different as it uses additional pair of ground and +5V outputs from ECU and its potentiometers are not connected together internally. Based on the above you should see close to 0V on blue wire (signal ground) and some strange voltage on white wire since it's an input and with disconnected sensor nothing drives it (except may be large resistor inside ECU but it's irrelevant detail). You should use blue wire as your reference 'ground' during your measurements of sensor's output signals as this is what it is for- to bring ECU's internal ground potential all the way to the sensors. ECU reads sensor voltages relatively to this wire, not some other 'ground' in the car. It is vitally important that this wire has good connection to correspondent ECU contact 58/70 and have no other current going through it- close to 0V voltage drop between TPS/APP end of the wire and correspondent ECU contact. Please don't 'ground' this wire on TPS/APP side to some other 'ground', it will make problem worse.

I wouldn't worry about voltage you see on the signal pins with disconnected sensors but the voltages you listed in your original post on blue wire are out of whack: it is ground and should be close to 0V at all times, regardless of sensor's position. Check its connectivity to correspondent ECU pin and if it's good- ECU ground itself.

sint3k

Blue on a 2003 maxima is Sensor throttle body sensor 2 "terminal 84"

Black on the throttle body is ground, i think your thinking of another vehicle.


http://workshop-manuals.com/nissan/m...ics/page_4401/

Anyways , all the sensors are within specs. I unplugged the ECU and the throttle body and did circuit checks to make sure the sensor wires are shorted to ground or power. Both Blue and White on the throttle body game back OL "Meaning no shorts". My last a final test was to short the 5v reference to sensor1 and sensor2 wiring and see if the ECU would reconize this. IT did on sensor1, but not on sensor 2, I'm starting to think i have an ECU issue. However the throttle body and everything work perfectly when the engine is not running and key on , no codes. So then again im leaning back towards a MAF issue because for a few seconds the ECU will control the thottle plate to achieve idle and then give up. I'm unable to get live data from this because my Auto Enguinity wont connect to this car but my crappy 70 dollar scan tool will.

sint3k

I Don't think you saw in my first post where everything is a 3.5 maxima in a 2.5 sentra shell. All the wiring and everything has been brough over from a 3.5 maxima.

Max_5gen

iTrader: (2)

That's what I thought- take a look at those FSM pages yourself. I might misread the color coding on the diagram where 'B' means Black and not Blue, my bad. BTW, sensor1 and sensor2 change their outputs in the opposite directions if I'm reading this correctly. So, to get the same effect you'd connect sensor2 input to the ground instead of 5V. This is my assumption based on FSM graph of their respective voltages.

sint3k

I'm going to try grounding the sensor that has 5 volts unplugged to see how the ECU responds "with what code". I just want to verify that the ECU is responding and correctly listening to the circuit at this point. Whats funny is on a 2003 Sentra 2.5 i unplugged the Throttle body and i got Circuit B high Code & a Circuit A high code. which uses a similiar throttle body actuator/sensor/connect from what i can tell. I'm also wondering if this is a airflow issue aka "the ECU is not seeing the RPM it wants to see and its blaming the throttle type deal" Anyways im not messing with this car anymore till saturday. Thanks for the reply if anything its helpful talking things out. I'm starting to hate this car

B=Black
L=Blue

sint3k

Well i corrected the bad grounds , they are now well below 100milivolts.
I did a circuit integrity test by grounding and jumping 5 volts to both sensors on the throttle body and both responded with the appropriate codes so the ECM is seeing it. Whats interesting is with the car off with key on posistion the throttle body works fine, no codes. But once you start it about 5 seconds after its running it seems its having problems finding its idle and then throws the code. I also tested some other grounds on the ECU and some of them are making a negative voltage on ground which is weird "No my leads are not backwards" I'm at a loss now because the Pedal and the throttle are all giving the correct voltages and grounds etc. Still got code p0221 and no throttle response when engine running