p2101- QG18DE

[Coheed]

Been getting this code on a 2006 sentra. Just replaced the TB with a Hitachi replacement factory unit, but still getting code.

The FSM says that either the wiring is bad, or the TB is no good. But since the TB is replaced, I was wondering who else has had this issue pop up or knows a common fix at this point.

Car starts fine. After clearing codes, idle is a bit high. Code gets thrown the first time you press the pedal. The FSM says that the pedal sensor will not throw this code, so I would guess this code is localized to just the TB or wiring. However, I don't want to keep throwing parts at this issue. It could be bad wiring, a bad ecu, bad ground somewhere...

Hopefully this issue is common enough that someone here can help. Google hasn't been helpful.

After replacing the TB, is it absolutely necessary to do the idle relearn immediately to prevent the code? Any info on this issue would be greatly appreciated.

[i68k]

who installed the tb? did you disconnect the battery before any electronics? did you make sure the terminals were tight and it has good ground contact? did you do all three of the relearns? but you are correct, if all else fails, you have to chase wiring or its a bad ecu, but you have plenty of other reasons to get this code. make sure you dont have dirty blue or green connectors, and wiggle the wiring, the stock pigtails sometimes go bad.


EDIT: your code is just a performance code, not a part failure code.
p2101 - electric throttle control performance

[Coheed]

Originally Posted by i68k

who installed the tb? did you disconnect the battery before any electronics? did you make sure the terminals were tight and it has good ground contact? did you do all three of the relearns? but you are correct, if all else fails, you have to chase wiring or its a bad ecu, but you have plenty of other reasons to get this code. make sure you dont have dirty blue or green connectors, and wiggle the wiring, the stock pigtails sometimes go bad.


EDIT: your code is just a performance code, not a part failure code.
p2101 - electric throttle control performance

The DTC lines read for the ECU are just for the motor. So the problem is with those two wires. I'm gonna check the wiring when I get some free time.

to answer your questions, I installed TB. The battery was disconnected. The connector seems tight. I will go through the full procedure in a few days when I get some free time. In the mean time, I am open to all suggestions!

[i68k]

Originally Posted by i68k

did you do all three of the relearns?

you have to do all 3 relearn procedures, or your tb/pedal wont work properly.

your trip code is a p2101, which is a performance code, not a part code, just saying it may not have been your tb that failed. meaning it could be a different part that is failing. the performance adjustment for the tb includes maf, tb, pedal, cam&crank sensors, ecu, and of course bad wiring in between any of those.

[Coheed]

Originally Posted by i68k

you have to do all 3 relearn procedures, or your tb/pedal wont work properly.

your trip code is a p2101, which is a performance code, not a part code, just saying it may not have been your tb that failed. meaning it could be a different part that is failing. the performance adjustment for the tb includes maf, tb, pedal, cam&crank sensors, ecu, and of course bad wiring in between any of those.

The FSM breaks it down into several tests.

None of these have anything to do with MAF, or any other sensor parts?

[i68k]

your maf is metering your air, and incorrect amount of air will cause a performance problem.

your cam and crank sensors are counting teeth to account for your crank/cam angles, if your trigonometry is slightly off, you will get a performance problem.

the fsm may not mention these parts immediate when troubleshooting, but they are responsible for inputs to the ecu that determine the performance of the motor. therefore, they are indirectly related to performance.

[Coheed]

Originally Posted by i68k

your maf is metering your air, and incorrect amount of air will cause a performance problem.

your cam and crank sensors are counting teeth to account for your crank/cam angles, if your trigonometry is slightly off, you will get a performance problem.

the fsm may not mention these parts immediate when troubleshooting, but they are responsible for inputs to the ecu that determine the performance of the motor. therefore, they are indirectly related to performance.

The performance issue relates directly to the TAC motor, not the engine itself.

[Coheed]

Here is my progress so far.

DTC p2101 is detectable on two circuits. The relay circuit, and the TAC motor circuit. However, a short or issue with the TAC relay circuit is detectable by itself with codes p2100 and p2103. So any issues with code p2101 that pertain to the TAC relay will throw one of these codes as well.

Nonetheless, I tested the full relay circuit. All wiring, the relay itself, and TAC fuse underhood are all in good operating condition.

I did the wiring checks between ECM terminals 4 and 5 with terminals 3 and 6 on the TAC harness. There are no shorts, and continuity is where it needs to be.

I tested the old TAC motors resistance and it came out to 30 ohms. The new one is at 2.5 ohms. The max limit is 15 ohms.

It's a tough one to call at this point, but all testing points out to a faulty ECM. The higher resistance in the motor could have contributed to a shortened lifespan.

[JudoJohn]

did you do all three relearn procedures?

[Coheed]

Originally Posted by JudoJohn

did you do all three relearn procedures?

The idle relearn happens practically by itself, the CEL comes on before you can perform this one. The TAC closed relearn happens by cycling the key a few times. Is there another relearn the FSM doesn't refer to?

[i68k]

Originally Posted by Coheed

The performance issue relates directly to the TAC motor, not the engine itself.

, glad your chasing wiring, it seems you are narrowing it down. also seems like you are following the fsm?

Originally Posted by Coheed

The idle relearn happens practically by itself, the CEL comes on before you can perform this one. The TAC closed relearn happens by cycling the key a few times. Is there another relearn the FSM doesn't refer to?

if the ses light comes back before the ecu can idle relearn, the problem still exist, or the relearns were not performed correctly. you need to do them in order successfully, to see all the prerequisites, use the fsm. did you confirm the operation of the throttle plate during your relearn?

assuming your battery terminals are tight, and you have good ground contact, im sure youve tested your battery voltage motor on & off. hopefully you dont have a short thats taking power from that circuit. that is a very high ohm reading you have, but im not sure the specs for this part.

you need to do all 3 relearns, in order, each one successfully. are you doing the pedal dance to do your relearn or are you using a scan tool/obd reader? if youre doing the pedal dance, and get the ses light to blink, your pedal is working. you can do each relearn 10x in a row if you are unsure if it was successful. once you know the pedal is working, you will have an input to your relearns. so..., you should be doing these:

1-accel pedal released position learning-if your ses light never blinks with pedal dance, either your dancing wrong, or your pedal is bad. normally the pedal is ok.

2-throttle plate closed position learning-you should be able to hear the throttle plate move, remember at least 10 seconds off, before you listen again. you can also remove the intake tubing and visually see the plate move. DO NOT MOVE THE THROTTLE PLATE WITH YOUR FINGER, or anything else.

-------you need to warmup the vehicle before an idle relearn will be successful, read the prerequisites in the fsm. let it idle, take it for a small drive, even if your idle is bouncing it is okay. this means your water temp gauge should be in the middle-ish somewhere.

3-idle air volume learning-basically here just follow the procedure, like the pedal dance, when you get to the end and the ses is showing your codes, you have to startup the motor on the next try. so prime your fuel and let it idle for at least 2-3 minutes before test driving. if it stalls, you need to do idle relearn over again until it idles correctly.

notes-remember to clear your codes, via pedal dance or obd reader, before you start doing relearns. once you got the ses light off, you should be good to do relearns. if the ses comes on right after you start the motor doing the idle relearn, the problem is immediate and still exist.

[Coheed]

Originally Posted by i68k

, glad your chasing wiring, it seems you are narrowing it down. also seems like you are following the fsm?



if the ses light comes back before the ecu can idle relearn, the problem still exist, or the relearns were not performed correctly. you need to do them in order successfully, to see all the prerequisites, use the fsm. did you confirm the operation of the throttle plate during your relearn?

assuming your battery terminals are tight, and you have good ground contact, im sure youve tested your battery voltage motor on & off. hopefully you dont have a short thats taking power from that circuit. that is a very high ohm reading you have, but im not sure the specs for this part.

you need to do all 3 relearns, in order, each one successfully. are you doing the pedal dance to do your relearn or are you using a scan tool/obd reader? if youre doing the pedal dance, and get the ses light to blink, your pedal is working. you can do each relearn 10x in a row if you are unsure if it was successful. once you know the pedal is working, you will have an input to your relearns. so..., you should be doing these:

1-accel pedal released position learning-if your ses light never blinks with pedal dance, either your dancing wrong, or your pedal is bad. normally the pedal is ok.

2-throttle plate closed position learning-you should be able to hear the throttle plate move, remember at least 10 seconds off, before you listen again. you can also remove the intake tubing and visually see the plate move. DO NOT MOVE THE THROTTLE PLATE WITH YOUR FINGER, or anything else.

-------you need to warmup the vehicle before an idle relearn will be successful, read the prerequisites in the fsm. let it idle, take it for a small drive, even if your idle is bouncing it is okay. this means your water temp gauge should be in the middle-ish somewhere.

3-idle air volume learning-basically here just follow the procedure, like the pedal dance, when you get to the end and the ses is showing your codes, you have to startup the motor on the next try. so prime your fuel and let it idle for at least 2-3 minutes before test driving. if it stalls, you need to do idle relearn over again until it idles correctly.

notes-remember to clear your codes, via pedal dance or obd reader, before you start doing relearns. once you got the ses light off, you should be good to do relearns. if the ses comes on right after you start the motor doing the idle relearn, the problem is immediate and still exist.

I've done everything there. The TAC motor is working properly, and you can see and hear it open during testing. I've probably cleared the lights 2 dozen times. The car throws the code the first time you touch the pedal. The pedal is commanding an open position, but the TAC isn't responding.

I did bypass the TAC relay. The engine was then able to rev normally, but it would bounce the idle around 3k rpm then back down.

The first trip detection logic finds this issue almost immediately upon starting the car. Engine light comes on, and limp mode is engaged. I started looking at other DTCs to see if they had any relationship with the P2101.

I wish I could test the power getting to the motor while the engine runs. But before power can be supplied, the CEL light comes on and inhibits further testing. I can send power to the TAC and confirm operation while the engine is running as well.

About the only thing I can think of is a computer issue. Perhaps the controller inside the ECM responsible for sending power is having an issue. All connections look good. No burnt or corroded terminals anywhere I can see. And, like I said, continuity exists where it should.

I'm half tempted to pull the ECM apart and take a look inside. See if I see anything that is burnt in there.

[i68k]

Originally Posted by Coheed

The car throws the code the first time you touch the pedal. The pedal is commanding an open position, but the TAC isn't responding.

are you doing the pedal dance or using a scanner/obd tool? what do you mean the pedal is commanding an open position? the pedal is an electronic part, its not cable driven. what are your voltage readings? you didnt replace your pedal, and still have your original pedal yes?

Originally Posted by Coheed

I did bypass the TAC relay. The engine was then able to rev normally, but it would bounce the idle around 3k rpm then back down.

this sounds like the relay is bad.... , but you can pull the ecu and check it out. make sure you disconnect the negative battery before pulling electrical connections.

you are using terms from a obd reader, like dtc, tac, cel. are you using a reader to perform your relearns? they may not be getting done correctly. if when you touch the pedal, and the ses light comes on, are you sure your pedal is working? have you done the pedal dance to pull your codes? if your pedal is bad, you will get mixed results, or no results.

does motor to startup and run, until you hit the pedal? does it idle normally, no misfires, no vacuum leaks?

[Coheed]

Originally Posted by i68k

are you doing the pedal dance or using a scanner/obd tool? what do you mean the pedal is commanding an open position? the pedal is an electronic part, its not cable driven. what are your voltage readings? you didnt replace your pedal, and still have your original pedal yes?



this sounds like the relay is bad.... , but you can pull the ecu and check it out. make sure you disconnect the negative battery before pulling electrical connections.

you are using terms from a obd reader, like dtc, tac, cel. are you using a reader to perform your relearns? they may not be getting done correctly. if when you touch the pedal, and the ses light comes on, are you sure your pedal is working? have you done the pedal dance to pull your codes? if your pedal is bad, you will get mixed results, or no results.

does motor to startup and run, until you hit the pedal? does it idle normally, no misfires, no vacuum leaks?

The relay circuit is tested with the OBD for codes P2100 and P2103. Code p2100 is circuit voltage for the relay coil. A short or open in this circuit will throw a p2100 code.

The P2103 is a problem with the relay output. A short or open in this circuit will throw code p2103.

Neither of these two codes are popping up. That being said, I did still check the full relay circuit. I also tested the relay off the car for proper operation, and it checks out perfect.

As far as the pedal, I have not replaced it. However, a malfunctioning part should trip a DTC P2122 or a P2123 (or p2127, p2128). The ECM uses the signals of the two sensors in the pedal sensor. These two values are compared to each other to determine a problem. But again, the computer doesn't see anything wrong with the sensor. If both sensors were bad, the pedal wouldn't respond with any sort of engine response, as it wouldn't know if/when you were pressing the pedal. Full throttle operation of the pedal while cranking will trigger the flood-control and prevent the injectors from firing. And that works fine.

I am using an OBD2 reader to erase codes, but not to do any on board functions. Just reading and erasing codes.

The engine starts up and runs perfect. Every time. Idles perfect, no missfires. No vacuum leaks. It will rev to 2000rpm and hold steady, as the limp mode prevents it from revving any higher. Clearing the light can occasionally see the engine rev up to 5k rpms before it trips the limp mode again.

[i68k]

im not sure where this is going....?

the pedal supplies an increasing voltage, and kink in one of the wires will increase resistance and cause a drop in voltage from the pedal, even a fraying or ripped off insulation from a wire next to a wire for the ecu, pedal or tb. as long as you have your original pedal, you should be good, when it actually malfunction it will throw pedal codes. when the voltages are slightly off, the ecu may assume normal operation if the voltages are within specs.

the related parts would be, ecu, tb, pedal, and electrical wiring. your indirect parts include maf, cam & crank sensors, o2 sensors, and a few more small items.

have you checked the voltages at the tb harness, many people have problems with the pigtail to the tb, getting dirty, old, or breaking wires.