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Old 07-27-2012, 10:49 PM   #1
OC_Nooby
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Member#: 311781
Join Date: Feb 2012
Location: Canada
Vehicle:
2003 WRX w STI V8

Default Hot Start issues. Can P0121 (TPS) cause this?

Hey Guys,

Battling one issue at a time. I took my car out for a ride and everything was perfect (A/F in spec cruise/WOT). When I got back I shut of the car and 5 minutes later was ready to take it out again. This time the car didnt fire up and I got a code for the TPS sensor P0121.

Could this sensor cause the car not to start? I've seen it light up before but id just erase the code.

This is my first drive with a 2.5L STI in my WRX (wrx harness/manifold). I replaced the CAM sensor as I had an issue with it. Took the car for a rip and now this.

Fires up when cold.

Gathered this info from my car:

Closed / Open (WOT)
Throttle Opening Angle 88.24 min 92.55 max
Throttle Sensor Voltage 3.8 min 3.94 max.

Doesn't seem right?

What should a stock wrx tps voltage measure. Car was off and I got this info with RomRaider logger.

Found this:

0.5V with throttle fully closed.
4.3V with throttle fully open.

Can someone confirm before I swap a TGV sensor for the TPS (TGV's deleted)
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Last edited by OC_Nooby; 07-29-2012 at 10:57 AM.
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Old 07-27-2012, 11:08 PM   #2
Ms Heatha
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Member#: 201949
Join Date: Feb 2009
Chapter/Region: SWIC
Location: Tahoe
Vehicle:
2000 2.5 RS
Red

Default

Throttle position sensor
Fully closed: 0.2 — 1.0 Fully opened: 4.2 — 4.7

Hope that helps
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Old 07-27-2012, 11:18 PM   #3
OC_Nooby
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Member#: 311781
Join Date: Feb 2012
Location: Canada
Vehicle:
2003 WRX w STI V8

Default

Quote:
Originally Posted by Ms Heatha View Post
Throttle position sensor
Fully closed: 0.2 — 1.0 Fully opened: 4.2 — 4.7

Hope that helps
Closed 0.2-1.0
Open 4.2-4.7

If I got that.

Thanks!

I don't have a weird idle. Maybe this affects me when the motor is warm and I'm flooding the car? (thinking out loud),
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Old 07-27-2012, 11:29 PM   #4
OC_Nooby
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Join Date: Feb 2012
Location: Canada
Vehicle:
2003 WRX w STI V8

Default

Ok well. I think its definitely the TPS.

Foot off the throttle I get 88% open. Now when I start slowly pressing the pedal nothing happens. Still reads 88% until I push down further (just a bit more then 3/4 pedal). So I can see why it would be fine on a cold start and crap on a hot start.

I'll replace said tps tomorrow and hopefully i'm right and can drive on
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Old 07-29-2012, 11:03 AM   #5
OC_Nooby
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Member#: 311781
Join Date: Feb 2012
Location: Canada
Vehicle:
2003 WRX w STI V8

Default

Fixed the problem. No more hot starts.

Now I get 0.5v closed throttle and 3.9v WOT. The tps angle/voltage increments nicely. I used my tgv motor as they are the same sensor / I did a TGV delete so it was laying around.
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