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P0122 Throttle Position sensor

Legacy 97 EJ22 TPS Throttle Position sensor P0122

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21 replies to this topic

#1 igammie

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Posted 14 November 2013 - 06:38 PM

Does anyone know which wire color is which?

I need to find my wiring problem.  I would guess Black is power, which I believe should be 5V?  Past that I am guessing.  Once TPS plug is removed finding live and ground should be easy; do I need to worry about finding the signal wire (0.2V right?) (other than inspecting all the wiring for wear).

If I am lucky There will be some worn insulation so the fix will be easy.  Otherwise I need to find a bad ground I am guessing?

Should any one have a diagnostics procedure or flow chart I would be REALLY grateful.  Thanks again!

Note Throttle position sensor has already been replaced, this is no longer intermittant and occors most days at start up.


Edited by igammie, 14 November 2013 - 06:39 PM.


#2 Fairtax4me

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Posted 14 November 2013 - 09:54 PM

What exactly occurs?
The code sets?
Any other symptoms?

Not sure of wire colors but 5v will be one side, signal will be the middle, ground is the other side.

The TPS does need to be adjusted so the ECU gets a signal of about 0.5v with the throttle closed. If you have 0.2v on the signal pin adjust the TPS so the signal pin is 0.5v and see if it still sets the code.

#3 igammie

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Posted 15 November 2013 - 05:50 AM

At start up it will generate two P0122, and a P1700; not always but 90% of the time.  When cleared it will generate the same.  It also has a rough (irregular) idle

This weekend I'll remove the sheathing and inspect all the wires, check for a bad ground and for 0.5V on the signal wires



#4 mikec03

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Posted 15 November 2013 - 09:08 AM

You may be wondering how to read the voltage [0.5v] at closed throttle?  When I replaced my sensor, also on a 97, I followed advise on this forum and stuck pins through two of the wires and put clips from the voltage meter on the pins.  Worked fine.



#5 ivans imports

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Posted 15 November 2013 - 11:19 AM

Had a 01 outback with a broken wire harness under intake kept giving tps code over and over sensers had been changed 3 times I changed intake wire harness and problem was gone and did not come back



#6 igammie

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Posted 15 November 2013 - 03:16 PM

Found this on another board:

 

from identifix:


Vehicle Application: 1997 Subaru Legacy SUS 2.5L 


Customer Concern: The check engine light is on with a code P0122 the Throttle Position Sensor (TPS) low signal. The TPS sensor was replaced. 

Tests/Procedures: 1. Verify the Red wire has 5-volts at the TPS sensor and the Black wire has a good ground. 


2. Check the White signal wire, it should have approximately 0.5 volts closed throttle and sweep up to 4.2 to 4.7 volts. If there is no voltage look for a grounded signal wire. 


3. If the voltage is correct, check for a open wire or a poor connection between the TPS sensor and the Engine Control Module (ECM). 

Potential Causes: Mis-Adjusted Throttle Position Sensor (TPS)

Wiring


Diagnostic Codes: P0122 

Author: Wayne Pasicznyk


#7 igammie

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Posted 20 November 2013 - 01:29 AM

OK Signal wire good, Live wire good and ground seems to be OK?  Anyone know what is an acceptable resistance between ground wire and battery negative.

Any idea what I need to check next?

 



#8 igammie

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Posted 20 November 2013 - 07:12 AM

Given I am running out of options, I need to check for a vacuum leak; I don't hear any hissing so I'll have to blow cigar smoke in there - I do not own a smoke machine....

If anyone has an idea where I should blow smoke in I'd be grateful for any input...

Thanks :)

MIght try this instead? - Homemade Smoke machine design: http://www.fiero.nl/...4-1-081547.html

 

 

Additional details - http://www.thesamba....ic.php?t=461116

 


 


Edited by igammie, 20 November 2013 - 07:27 AM.


#9 grossgary

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Posted 20 November 2013 - 09:05 AM

wow, nutty.  at this point i'd get the FSM and verify every step with 100% accuracy.

 

for vacuum leaks - just spray carb cleaner or starting fluid around the engine bay while idling or cranking it - when the fluid hits a leak the RPM's will notably change due to "more fuel" getting in with the intruding air.



#10 ivans imports

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Posted 20 November 2013 - 09:51 AM

Have you checked the main engine harnes conectors are pluged in all the way and no bent pins



#11 Fairtax4me

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Posted 20 November 2013 - 05:58 PM

Now you need to check signal voltage at the ECU. Find the ECU I/O pinout chart for your year so you know which pin to check.

If ground were no good signal return voltage would be high.

#12 igammie

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Posted 21 November 2013 - 12:48 AM

I will check all the harness connections today.  I have continuity between ground cable and Battery post; so that is not issue.

Signal wire is 0.5V (near as dammit).

Since I have an irregular idle, Carb cleaner won't work, as well.

The ECU is in the passenger footwell, right?

It is a 1997 Legacy L EJ22; do you have any idea where I'd find a 'pinout chart' and test procedure?

Unfortunately my Factory Service Manual has very little on this.

It still triggers 2 x P0122 and a P1700 at every start.  If I clear they come right back.  My daily commute is 33 miles it is 'stuttering' (loses about 500 RPM for about 3 seconds) about ten miles into this drive, while on Cruise control, and continues until I get to work.  I fear I might have to bite the bullet and find a good auto electrician?

Thank you all for your input, I'll be honest auto electrics is not my strongest area; I am really grasping at straws to try to fox this...


Edited by igammie, 21 November 2013 - 06:50 AM.


#13 Fairtax4me

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Posted 21 November 2013 - 01:35 AM

If you have a factory service manual the info you need should be in there, but some things are difficult to find.
The chart should be in the troubleshooting section. But if you can't find that look in the wiring diagrams for electronic engine controls. The TPS wiring will be there and should show which color wire and which pin it attaches to the ECU with a picture of the ECU connector at the bottom of the page.
Once you find the right pin, check for voltage on that pin with the connector plugged in. If its less than 0.5v unplug the ECU connector and use a long jumper wire to check for resistance to the TPS connector.
Also check for dirt/corrosion in the terminals.

#14 igammie

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Posted 21 November 2013 - 02:13 AM

I'm digging....

Is the ECU in the passenger footwell?  (when I get there....  I have to find the damn wiring diagram first)

Thanks!

 



#15 igammie

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Posted 21 November 2013 - 02:41 AM

I think I found it; now I have to try to understand and use it!

http://prntscr.com/25ng9i

 

OK, I think; that I need to check for 5V on #21 at ECM, and 0.5V (at idle) at #6.  If I got that wrong please correct me :)

Oh can someone, anyone, tell me where to find the Engine Control Module?  I think it is in passenger footwell, but, I don't know...

FSM Throttle Position sensor

 

http://prntscr.com/25nk41


Edited by igammie, 21 November 2013 - 03:19 AM.


#16 igammie

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Posted 21 November 2013 - 10:36 AM

All under-hood connections are good; the ones I have removed I detached again and sprayed male and female sides with electrical contact cleaner.

Found some slack in Cruise Control Throttle cable and dealt with that.  I fear I might have found a job beyond my skill?  I'll keep trying and testing, until there is nothing left; then I fear I'll have to pay someone with more skill than me? (which is a pretty big group of people!)



#17 Fairtax4me

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Posted 21 November 2013 - 11:02 AM

ECU is under the carpet in the passenger floor up under the dash. Two or three clips and pull the carpet back then remove 3 10mm bolts and a 10mm nut at the top of the metal plate. Remove that then the ECU is staring you right in the face.

#18 lewisd

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Posted 10 December 2013 - 01:06 PM

99 legacy wagon EJ22. I've got the same exact codes throwing every time. trying to get CEL out for emissions inspection.  any update on this?



#19 igammie

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Posted 12 December 2013 - 01:21 AM

I have not resolved it; I am just stubborn and still trying.  I hate not finding out what is causing it.  not given up; I fear I might end up either buying a power probe, or paying someone with more skill than me?

I used to be an Alfa Romeo nut, electrical problems are fortunately much rarer with the Suby.

 



#20 WoodsWagon

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Posted 13 December 2013 - 12:19 PM

Have you verified it's set right at closed throttle? I bought a 96 that had both the same codes and the previous owner had replaced the TPS. I plugged my OBD2 scan tool in, looked in the live data stream, and adjusted the TPS so that it just tipped over from 1% to 0% at closed throttle. There's a large range of 0% in the adjustment, so you want it set right where it breaks over into 1%. No more codes.



#21 igammie

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Posted 13 December 2013 - 01:51 PM

I set it by voltage...

My scan tool is quite basic; I'll have a look and see if I can access that data?



#22 Fairtax4me

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Posted 13 December 2013 - 11:09 PM

Have you checked signal voltage at the ECM?
If you have 5v at the sensor, reference voltage at the ECM is fine.
Did you check for resistance on the ground wire at the sensor? (Needs to be unplugged)





Also tagged with one or more of these keywords: Legacy 97, EJ22, TPS, Throttle Position sensor, P0122

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