02 EX - P0122 TP Sensor Circuit Low Voltage - Honda Civic Forum

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02 EX - P0122 TP Sensor Circuit Low Voltage

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Old 04-16-2015
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02 EX - P0122 TP Sensor Circuit Low Voltage

I got this coming home from the post office. Nothing seemed immediately wrong to me but I was going pretty slow the last few blocks after I noticed the CEL. I've been googling trying to figure out what to check first. I have a cheap bluetooth thing that gives realtime data. It only shows percents for the throttle position. It showed 9% at closed and 91.4% fully opened. I wasn't sure how to interpret that.

Are those values close enough to 10% and 90%?

I have a multimeter should I go on to the testing the wire voltages step?

Do I need to remove the filter box to see the sensor?

Where are the ECM/PCM wires that it says I should check?

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  1. Turn the ignition switch ON (II).
  2. Check the throttle position with the scan tool.
Is there about 10% or 0.5 V when the throttle is fully closed and about 90% or 4.5 V when the throttle is fully opened?
YES
- Intermittent failure, system is OK at this time. Check for poor connections or loose wires at the TP sensor and at the ECM/PCM.
NO
- Go to step 3.
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Old 04-16-2015
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Re: 02 EX - P0122 TP Sensor Circuit Low Voltage

It showed 9% at closed and 91.4% fully opened.
Your % values are pretty close. You can double check with a voltmeter if you wish.

Actual voltage at closed throttle is usually 0.49v and this number is extremely consistent across the entire car line. Look for smooth linear increase all the way to about 4.5v at wide open throttle.
Push, pull, wiggle the sensor and connector, the readings should stay rock steady.
P0122 TP Sensor Circuit Low Voltage
I'd be interested in freeze frame data to see what the value was when the code set.

Do I need to remove the filter box to see the sensor?
Yes because the sensor is attached to the side of the throttle body.

Where are the ECM/PCM wires that it says I should check?
As long as the TPS values are correct while you view them (i.e. 0.49v at closed throttle) all wiring between sensor and PCM is intact.

Best you can hope to find is something like loose pin fit during a wiggle test.
Wiggle wire harnesses between the TPS and computer while watching the scanner, see if values change when they should be steady. If the reading makes a big change you may be on to something.

It helps if your scan device has a fast update rate. If it takes several seconds to update a reading you may never be able to read a momentary glitch. Voltmeter may be better for this as it should read much quicker than the scan device..
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Old 04-16-2015
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Re: 02 EX - P0122 TP Sensor Circuit Low Voltage

0.46v closed. 4.55 fully open. It wasn't easy to hold the probes and open the throttle but it seemed to be a smooth increase. from bottom to top. I guess the question is, is .46v too low? If not what's the next step, clear the code?

If the sensor is bad what are my options? Do I have to get a whole new throttle body? Is used a possibility, if so what should I look out for?

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Old 04-17-2015
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Re: 02 EX - P0122 TP Sensor Circuit Low Voltage

I'd clear the code and see how long it takes for the same code to come back.

IS .46 too low? Maybe, maybe not. It's pretty close, but I'd like to see what a scanner says, as your voltmeter may not read exactly the same as what the computer is seeing.

.46v alone did not cause the code.
The computer had to see 0.23v or less, for at least 2 seconds in order to set the code..

Freeze frame data would help. That way we can hopefully see what the voltage was at the time the code set.
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Old 04-17-2015
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Re: 02 EX - P0122 TP Sensor Circuit Low Voltage

I cleared it and made a short trip and it didn't come back. I'll keep an eye on it and definitely be back if it comes back on.

Thanks again for all your help.
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Re: 02 EX - P0122 TP Sensor Circuit Low Voltage

Originally Posted by tkcne View Post
I cleared it and made a short trip and it didn't come back. I'll keep an eye on it and definitely be back if it comes back on.

Thanks again for all your help.
backprobe the wires your checking using pins, use alligator clips attached to your leads.
great guide below for checking the TPS wiring:
http://honda-tech.com/honda-crx-ef-c...hread-2830131/
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Re: 02 EX - P0122 TP Sensor Circuit Low Voltage

backprobe the wires your checking using pins, use alligator clips attached to your leads.
That's pretty much exactly what I did to get the voltage. Thanks for the link. That will be useful if the problem comes back.
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Re: 02 EX - P0122 TP Sensor Circuit Low Voltage

Originally Posted by tkcne View Post
I cleared it and made a short trip and it didn't come back. I'll keep an eye on it and definitely be back if it comes back on.
If it's THAT intermittent or random, I'll kinda lean toward a sensor fault instead of a wiring issue.

It's damn hard to make a determination while it's all working correctly.
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Old 04-18-2015
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Re: 02 EX - P0122 TP Sensor Circuit Low Voltage

I put a little more than 50 more miles on it tonight and it's still off. That one time is the only time I've ever seen it. You think the actual sensor itself might be bad?
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Re: 02 EX - P0122 TP Sensor Circuit Low Voltage

Originally Posted by tkcne View Post
I put a little more than 50 more miles on it tonight and it's still off. That one time is the only time I've ever seen it. You think the actual sensor itself might be bad?
maybe:
Originally Posted by ezone View Post
If it's THAT intermittent or random, I'll kinda lean toward a sensor fault instead of a wiring issue.

It's damn hard to make a determination while it's all working correctly.
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