trouble code 21
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trouble code 21
i had my car on the smog dyno getting ready to be tested when it idled up on its own for a few seconds and set the code.we shut it off and restarted it and it wont idle now.changed tps and cleared code and it didnt help.changed ecm no help. HELP!!!!!!!!!!!!
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From: Lubbock for now, headed for Oklahoma
Why did you change the ECM??? If they had their system plugged into it it most likely interrupted or glitched the ECM and caused it to loose it's learned idle. There is a simple procedure for idle relearn or reset if needed.
The code 21 is for a high Throttle position sensor voltage. I would try disconnecting the battery and waiting for 5 minutes. hook it back up and start the car. Do not touch the throttle! Just let it sit and relearn its idle. Let it idle until the fan kicks on and back off. Also be sure to check the connector at the TPS and the wires going to it. If they were screwing around in there for the IM240 a lot of shops will make problems to get a good sale. Looks like they may have already.
The code 21 is for a high Throttle position sensor voltage. I would try disconnecting the battery and waiting for 5 minutes. hook it back up and start the car. Do not touch the throttle! Just let it sit and relearn its idle. Let it idle until the fan kicks on and back off. Also be sure to check the connector at the TPS and the wires going to it. If they were screwing around in there for the IM240 a lot of shops will make problems to get a good sale. Looks like they may have already.
Last edited by BluRay; Dec 28, 2008 at 06:24 PM.
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From: Lubbock for now, headed for Oklahoma
Pro
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From: Lubbock for now, headed for Oklahoma
In that case it has shorted the TPS. Replace it and I am confident you'll be fine. Requiring WOT along with the 21 code is a pretty good indicator that the TPS has shorted to ground and is showing the computer 5 volts all the time. Therefore requiring WOT to match the amount of fuel delivered.
No amount of adjusting will help this. Just a new TPS.
No amount of adjusting will help this. Just a new TPS.
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i already tried replacing it and got no change so i tested the voltage at the b pin on the plug.then put the old one back on and got the same readings. but the voltage goes from about .6 to no more than 4.3. thats why i changed the ecm.
Pro
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From: Lubbock for now, headed for Oklahoma
The ECM has nothing to do with that. That is normal. Most of them do not reach a full 5 volts. There is a short somewhere. You need to get some data from the ECM and see what it sees. It's very possible it is seeing 5 volts regardless of what is at the sensor. If you don't have access to a scan tool you can check the voltage at the signal wire at the ECM connector. Just back probe the wire while it is connected. then turn the key on.
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Race Director
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From: The Top of Utah
Originally Posted by sweets
changed tps and cleared code and it didnt help.changed ecm no help. HELP!!!!!!!!!!!!
Originally Posted by BluRay
...caused it to loose it's learned idle. There is a simple procedure for idle relearn or reset if needed.
I'd be looking for a short in the wires between the TPS connector and the ECM.
RACE ON!!!
Pro
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From: Lubbock for now, headed for Oklahoma
Why did you change the TPS? Did it test bad?
The idle speed is not "learned". It is programmed into the chip. The ECM will not unlearn (forget) the programmed idle speeds. There is a procedure for acclimating the IAC upon (re)installation, but it has nothing to do the the TPS or a code 21.
I'd be looking for a short in the wires between the TPS connector and the ECM.
RACE ON!!!
The idle speed is not "learned". It is programmed into the chip. The ECM will not unlearn (forget) the programmed idle speeds. There is a procedure for acclimating the IAC upon (re)installation, but it has nothing to do the the TPS or a code 21.
I'd be looking for a short in the wires between the TPS connector and the ECM.
RACE ON!!!
yeah it just seemed a better way of explaining it.
Race Director
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From: The Top of Utah
Originally Posted by BluRay
yeah it just seemed a better way of explaining it.
Originally Posted by sweets
i believe that a short is what it has come down to.my book tells me what pins to test at the comp. ill have to do this tomorrow. thank for all of your input.
RACE ON!!!
Pro
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From: Lubbock for now, headed for Oklahoma
That something may have been reported to it that caused it to change the idle settings. Not that it was going to learn an actual idle. I have seen vehicles get a diagnostic system hooked to them and have all kinds of issues depending on the software. Often all it takes is a battery disconnect for them to return.
Sorry should have watched my terminology and said what I meant.
Sorry should have watched my terminology and said what I meant.
Le Mans Master
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From: Myrtle Beach SC
St. Jude Donor '05-'06
He is a stickler for correctness but knows his stuff. He kinda grows on you especially if you are not the target. Good to see ya posting CFI
Pro
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From: Lubbock for now, headed for Oklahoma
It shows sometimes.......
Le Mans Master
Joined: Dec 2004
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From: Myrtle Beach SC
St. Jude Donor '05-'06
Well CFI has called many people on the carpet including me but he is rarely wrong when he does. He is known for his "tactful manner".He is one of the few valuable sources that still are allowed to be here any more a lot got banned or just bailed. Just so you don't take it personal at least you are trying (like me) if you don't try you can't fail.
Pro
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From: Lubbock for now, headed for Oklahoma
Well CFI has called many people on the carpet including me but he is rarely wrong when he does. He is known for his "tactful manner".He is one of the few valuable sources that still are allowed to be here any more a lot got banned or just bailed. Just so you don't take it personal at least you are trying (like me) if you don't try you can't fail.
Melting Slicks
Joined: Oct 2004
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From: Austin Texas
Those voltages you measured are correct, your TPS is fine !! The TPS is nothing more than a resistor divider. There are no active circuits in your TPS, just a circular resistor coil and a brush contact. The reference voltage going to the TPS is 5v, which is SUPPLIED by the ECM. So, in a perfect world, the best you could ever see would be between 0V and 5V. But The TPS is not a perfect resistor, and you will never see a perfect 0v(complete short) or 5V(complete open). So.. 0.6V(idle) and 4.3V(WOT) are acceptable voltage measurements.
Pro
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From: Lubbock for now, headed for Oklahoma
"but the voltage goes from about .6 to no more than 4.3. thats why i changed the ecm. "
Those voltages you measured are correct, your TPS is fine !! The TPS is nothing more than a resistor divider. There are no active circuits in your TPS, just a circular resistor coil and a brush contact. The reference voltage going to the TPS is 5v, which is SUPPLIED by the ECM. So, in a perfect world, the best you could ever see would be between 0V and 5V. But The TPS is not a perfect resistor, and you will never see a perfect 0v(complete short) or 5V(complete open). So.. 0.6V(idle) and 4.3V(WOT) are acceptable voltage measurements.
Those voltages you measured are correct, your TPS is fine !! The TPS is nothing more than a resistor divider. There are no active circuits in your TPS, just a circular resistor coil and a brush contact. The reference voltage going to the TPS is 5v, which is SUPPLIED by the ECM. So, in a perfect world, the best you could ever see would be between 0V and 5V. But The TPS is not a perfect resistor, and you will never see a perfect 0v(complete short) or 5V(complete open). So.. 0.6V(idle) and 4.3V(WOT) are acceptable voltage measurements.
lol, MY TURN! while we are punching for terminology. A TPS is a potentiometer....