code 21 high idle
Thread Starter
Advanced
Joined: Dec 2005
Posts: 58
Likes: 0
code 21 high idle
89 vett set a code 21 tps. tps tested good. changed out ecu no difference.could not get it to set a code 22 in testing.reset the iac to correct the idle and when it sets the code again i start it back up and the idle is back up to 1500 to 2000 rpms. HELP
Le Mans Master
Joined: Jan 2003
Posts: 5,858
Likes: 7
From: Santa Maria CA
That's you problem right there. 0.7 volts is too high. Code 21 means the voltage signal from the TPS is too high. This causes your high idle.
Factory spec is .54 volts with throttle closed (idle or key on). Backprobe the two upper TPS wires with a voltmeter while leaving the TPS connected. Engine does not have to be running, just the key needs to be on. Loosen both torx screws and move the TPS by hand till you get .54 volts with throttle closed, and about 4.0 volts wide open. Restart car and report back.
Factory spec is .54 volts with throttle closed (idle or key on). Backprobe the two upper TPS wires with a voltmeter while leaving the TPS connected. Engine does not have to be running, just the key needs to be on. Loosen both torx screws and move the TPS by hand till you get .54 volts with throttle closed, and about 4.0 volts wide open. Restart car and report back.
Last edited by 86PACER; Jan 19, 2009 at 09:17 AM.
Le Mans Master
Joined: Jan 2003
Posts: 5,858
Likes: 7
From: Santa Maria CA
Yes, factory spec setting is .54. Idle starts to rise real high once you start going about .70 volts and higher. Is this your old TPS or a new unit? I've gotten bad ones right out of the box that don't allow for a proper setting like you are describing.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Team Owner
Joined: Jan 2003
Posts: 20,315
Likes: 245
From: Summerland B.C. Canada
