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P0121 TPS code (installed new Mopar TPS but still runs rough and throws code again)


John Wolf

Member
Joined
Oct 8, 2018
Messages
75
Location
Eastern NC
Ok, I've cleaned the IAC and TB 3 times, changed O2 sensor, and I'm on the 3rd TPS, last one being a mopar I bought at dealer for $100. Same issue keeps coming up within minutes of clearing the code out (always P0121) and cranking up, as soon as I try to accelerate. The idle is all over the place too, sometimes hovering around 1200-1400, then dropping, but never steady and stable like it used to be at around 800. I have a mopar IAC coming Wed. Can a bad IAC come up as a TPS code and make the engine sputter and buck under load? Acceleration is sluggish even when it's not sputtering. What else am I missing?
 

Byhumba

Learning phase
Supporting Member
Joined
Jul 4, 2018
Messages
252
Location
SoCal, USA
How many miles have you driven with the new TPS sensor? My Jeep gave that same code and had an erratic idle. Replaced the old TPS with a Mopar one from the dealer. Mine started revving up and would be in the 1,200 to 1,500 RPMs at a red light after installation. It resolved on it's own after about 25 miles or so.
 

ItchyDong

Airframe & Powerplant LJ Mechanic
Supporting Member
Joined
May 20, 2020
Messages
29
Location
Dothan, Alabama
As said, continuity and loaded circuit power checks. Make sure you've got 5 volts going to the TPS with engine running. My bet is something is fruity with the signal wire. Check continuity back to the PCM. Just like everyone said. Wiggle Wiggle. Check for corrosion or loose sockets inside of the connector too.
 

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John Wolf

John Wolf

Member
Joined
Oct 8, 2018
Messages
75
Location
Eastern NC
I have rattled the wiring all the way up to the ecm with no effect but when I got there I noticed the Jet Performance chip on the ecm, installed by PO (forgot it was there frankly). Took that off and so far no codes for about 10 miles. I'll keep driving to see if sputtering starts up again but I like the idea of system relearning over time with Mopar tps! Will update after I've driven it for a while. Never liked the Jet chip but it was there when I bought it 3 yrs ago so left it. Gone now!
 

CharlesHS

TJ Enthusiast
Supporting Member
Joined
Mar 10, 2020
Messages
819
Location
Carmel Mountain
I have rattled the wiring all the way up to the ecm with no effect but when I got there I noticed the Jet Performance chip on the ecm, installed by PO (forgot it was there frankly). Took that off and so far no codes for about 10 miles. I'll keep driving to see if sputtering starts up again but I like the idea of system relearning over time with Mopar tps! Will update after I've driven it for a while. Never liked the Jet chip but it was there when I bought it 3 yrs ago so left it. Gone now!
Years ago I had a similar problem with a '98 XJ 4.0L that I had installed a Jet Performance chip onto the ECM. I checked all the 32 pins on the ECM and the connector, but the problem turned out to be the Jet chip which had been installed for about 15 years. The problems remained gone once I removed the chip. I sent the chip back to the manufacturer and they replaced the chip for free.
 
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John Wolf

John Wolf

Member
Joined
Oct 8, 2018
Messages
75
Location
Eastern NC
Knock on wood, I've been driving it since removing the Jet chip and no cel and runs just as good as before any of these problems surfaced. So far no sputtering or missing either. Seems to be running fine but will know this weekend when I drive it to the beach!! 3 hrs each way.
 
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