5.0L (1979-1995) Mustang Technical discussions on 5.0 Liter Mustangs within. This does not include the 5.0 from the 2011 Mustang GT. That information is in the 2005-1011 section.

Code 121 help.

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Old Sep 13, 2021 | 08:11 PM
  #1  
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Zeaton11
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Default Code 121 help.

I had another post a few days ago. I had codes for ECT ACT and TPS. After tracking down cut wires, I reattached the new pigtail for the ECT, replaced the ACT sensor and tested to see if the TPS(122) would go away because the gry/rd wire was cut at the ECT. Code was still present, replaced the TPS. Found no voltage at anything to the TPS harness. Again, tracked down and where the EGR??? sensor was, the common 5v and gry/red were cut. I connected the brn/wht again, now I have 5v to the TPS. New problem, 121. What do I do with 121? TPS at idle is set at .95, has 5v ref. Code will not go away. Does the left over gry/red at EGR need to be attached to anything? Car falls flat on its face when I shift to second WOT. I did turn the FPR down from 55 to 38 and it kind of helped but still runs like shut.

All codes pulled today.
O
121
327
C
327
R
412
121
314
311
327

Smog pump and egr are not around.
Old Sep 15, 2021 | 12:53 PM
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Did you remove all of the emissions equipment?
Old Sep 15, 2021 | 04:18 PM
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It looks like everything has been removed. I haven't had it that long, I see the wires were cut off at the harness for egr, there is a pulley where the Smog pump would be. I think it is all removed
Old Sep 15, 2021 | 04:40 PM
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I've read that can cause issues with hesitation and such since your computer thinks that the egr and smog pump will be putting in additional air (several of those codes are emissions related). Has the car been tuned? I had my tuner just remove the emissions stuff from the tune and I've never had a problem. Surprised it's doing it a wot though, I though those all closed off under full acceleration.
Old Sep 15, 2021 | 04:58 PM
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I found one of those sct/Bama chips in the glove box, maybe somewhere on there is a crappy tune that has it all deleted. As much stuff that wasn't hooked or and chopped harnesses it almost looks like someone was about to run a carb, then gave up and it was all in pieces until I got it and started to put stuff together.
Old Sep 16, 2021 | 11:47 AM
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You can get a moates quaterhorse for relatively cheap and get into the tune your self, I'm not sure how involved it is though. A few other guys around here have done there own hopefully they can chime in. I guess otherwise all you can do is follow the wiring diagrams and hook everything back up that you can
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