Reduce speed Engine
Thread Starter
Intermediate
Joined: Aug 2019
Posts: 36
Likes: 4
Reduce speed Engine
Hey guys.. Little background. I have a 2001 z06, ms4, long headers, vararam intake, fast intake manifold and ls2 TB.. lately I got the reduce speed engine light on my dashboard
Pull the codes a p1220 and p122 came up
Before I get a new ls2 TB l was thinking to replace the ls2 harness adapter when we did the work we bough a cheap one on amazon. Any thought I will really appreciate it.
Thank you
Pull the codes a p1220 and p122 came up
Before I get a new ls2 TB l was thinking to replace the ls2 harness adapter when we did the work we bough a cheap one on amazon. Any thought I will really appreciate it.
Thank you
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,319
Likes: 3,927
From: Cape Coral, Florida
The P1220 is the PCM doesn’t like the TPS 2 voltage...it’s seeing less than .13 volts at idle or more than 4.87 volts at WOT...you will have to check the TPS 2 signal wire with your DVOM...don’t know what your last DTC was...the last digit is missing...now this was all happening with your stock TB installed ???
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,319
Likes: 3,927
From: Cape Coral, Florida
So these DTC’s were right AFTER the LS2 TB install ??...was it running OK since the install for a time ??...so you are saying it was good for 5 months and then it happened about a month ago ???
Last edited by C5 Diag; Apr 30, 2020 at 05:53 PM.
Thread Starter
Intermediate
Joined: Aug 2019
Posts: 36
Likes: 4
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,319
Likes: 3,927
From: Cape Coral, Florida
You’ll have to check that TPS 2 signal wire (pink) with a DVOM and see what voltages you have...the TAC motor harness disconnected and TB fully closed you should have 4.3-4.8 volts and at WOT should be .13-1.0 volts !!...video enclosed...you will have to back probe the pink wire so have a T pin or something similar handy !!...you have a TPS1 signal wire also..the voltages move in opposite directions if you were to check TPS1.
Last edited by C5 Diag; Apr 30, 2020 at 06:07 PM.
Thread Starter
Intermediate
Joined: Aug 2019
Posts: 36
Likes: 4
You’ll have to check that TPS 2 signal wire (pink) with a DVOM and see what voltages you have...the TAC motor harness disconnected and TB fully closed you should have 4.3-4.8 volts and at WOT should be .13-1.0 volts !!...video enclosed...you will have to back probe the pink wire so have a T pin or something similar handy !!...you have a TPS1 signal wire also..the voltages move in opposite directions if you were to check TPS1.
https://youtu.be/8KfKfImoIXg
https://youtu.be/8KfKfImoIXg
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,319
Likes: 3,927
From: Cape Coral, Florida
If I knew I could troubleshoot from home and make millions !!...you have to test !!...if you have a bad ground for instance and it’s elevated your 4.8 voltage may go to 4.9 or 5 volts and BOOM..your P1220 !!...signal ground should not be more than 100Mv (.1 volts)...it’s a purple for TPS1 and white for TPS2. I know members have issues with this conversion because of the pin outs of the 2 circuits !!...BTW a voltmeters refresh rate is very slow so if that voltage did spike over 4.8 volts you may miss it with a voltmeter...I always scope TPS circuits !!
Last edited by C5 Diag; Apr 30, 2020 at 06:29 PM.
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Burning Brakes
Joined: Aug 2011
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If you also get it tuned then dont waste your time with a silver blade TB. Get a gold which are readily available and tune it to work. It has been done and in the long run will be cheaper then to keep buying used pieces that will break also.
Thread Starter
Intermediate
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