TPS issues with BBK throttle body
Thread Starter
Staging Lane
Joined: Jun 2015
Posts: 96
Likes: 3
From: Melbourne, Australia
TPS issues with BBK throttle body Hi guys, getting TPS codes (p0121) if I'm idling in gear. No issues if I'm in neutral. If I put it in gear, the light will come on after about 30 seconds, or only 15 if the air con is on. Initially I noticed my TPS voltage was a bit low at idle, around .42V, so I adjusted my stop screw, tune, and wound the TPS around slightly to bring my minimum voltage up to .76V. Still no joy.
I know the obvious solution is to throw a new TPS at it, but I'm not sure when it's fine in neutral, and only has an issue when it's in gear.
Any help would be much appreciated. Cheers, Ben
I know the obvious solution is to throw a new TPS at it, but I'm not sure when it's fine in neutral, and only has an issue when it's in gear.
Any help would be much appreciated. Cheers, Ben
Thread Starter
Staging Lane
Joined: Jun 2015
Posts: 96
Likes: 3
From: Melbourne, Australia
Build was done a few years back, but I've only just purchased the car. Neither of the last two owners were responsible for the build either. I did see in an old forum post from two owners ago that he was having the same issue, so it MAY have been there from the start.
No stock cam, I could definitely get one but highly unlikely that I'd go to the effort of changing it without at least throwing a TPS at it first.
LS1, normal LS1 PCM. I can post both, but I don't think either contains any useful info. I was watching TPS voltage in the logger, at idle it never varied more than .02V (.76 to .78) the whole time, whether in neutral or in gear. I was careful not to touch the throttle at any point while trying to diagnose it.
No stock cam, I could definitely get one but highly unlikely that I'd go to the effort of changing it without at least throwing a TPS at it first.
LS1, normal LS1 PCM. I can post both, but I don't think either contains any useful info. I was watching TPS voltage in the logger, at idle it never varied more than .02V (.76 to .78) the whole time, whether in neutral or in gear. I was careful not to touch the throttle at any point while trying to diagnose it.
Staging Lane
Joined: Jan 2017
Posts: 67
Likes: 1
please post the tune and data log.
I am no expert, but to my understanding in the tune there are settings that compare the TPS signal to the map signal. If they dont match, the PCM assumes the TPS is bad and throws a P0121 code.
Since a big cam changes the idle vacuum thats why I asked if it was stock cam. Also may explain why it happens only in gear and even faster with AC on.
you can read into this more to see if this may be your issue. In HP tuners -> Engine Diag - > Airflow -> P0121 Error min\max map
I am no expert, but to my understanding in the tune there are settings that compare the TPS signal to the map signal. If they dont match, the PCM assumes the TPS is bad and throws a P0121 code.
Since a big cam changes the idle vacuum thats why I asked if it was stock cam. Also may explain why it happens only in gear and even faster with AC on.
you can read into this more to see if this may be your issue. In HP tuners -> Engine Diag - > Airflow -> P0121 Error min\max map
Staging Lane
Joined: Jan 2017
Posts: 67
Likes: 1
Some more info on what I think the issue may be.
https://www.hptuners.com/forum/showt...the-P0121-Code
https://www.hptuners.com/forum/showt...the-P0121-Code
Thread Starter
Staging Lane
Joined: Jun 2015
Posts: 96
Likes: 3
From: Melbourne, Australia
Compsystems, you are a good man! That sounds exactly like my issue (with the added TCS deal and shifting into fourth at very low MPH). With my cam I idle right around 65-70kpa too. Can't believe I didn't find that thread in all my searching.
I'll sort the tune out when I get back to the car tomorrow. Thanks again! That's a very valuable bit of information to have.
I'll sort the tune out when I get back to the car tomorrow. Thanks again! That's a very valuable bit of information to have.
