Throttle issues (long)
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1st Gear
Joined: Nov 2021
Posts: 1
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Throttle issues (long)
hi so i’ve been having an issue with my c5’s throttle system for the past few months and i can’t find anyone else with the issues i’ve been having. i’m pretty much at my breaking point with this car.
Here’s my issue. the car has thrown just about every possible throttle code you can have. p1120, p1121, p1515, p1516 etc etc. at this point i have replaced just about every piece in this car that has anything to do with the throttle system. as many of you know, once any of these codes pop up, the car will go into “reduced engine power” mode. the issue with my code is that it is extremely intermittent and random when it happens. the code has popped up on idle immediately after start up, on the freeway, just driving normally, and driving the car hard. i have had to pull off to the side of the road way more times than i could possibly count to clear the code with my obd scanner.
the first part i replaced was the tps (throttle position sensor), located on the right side of the throttle body. that did not fix it. after that i checked the pins that ran into the connector for the tps, in order to check for any sort of damage or missed contact points. it all was mint. i cleaned all the grounds that had anything to do with the cars engine and basic engine computers. i assumed this would be the issue bc that’s the only bit of help and information people know to offer when it comes to electronic issues on a c5. it did not fix it. every inch of cable running from the throttle pedal to the tac module and from the tac module to the throttle body has been checked. i looked for possible corrosion on the tac module and the wiring harness (sitting under the battery) for possible damage. there WAS corrosion from a past owners leaky battery, but no actual damage to components. i replaced the tac module itself, and it’s still not fixed. really the only piece left to replace on this car is the throttle actuator itself but i inspected it and it looked fine (gears were all mint and the pins and connections were too. i also hooked up a scanner that would read how much the throttle body was open and it passed my little test just fine)
at this point i’m really not sure what to do. the car hasn’t ran normally since when i first bought it about half a year ago and it’s the only issue this car has actually ever had.
anyone have any ideas on what to possibly do? thanks for reading!
and yes i cleaned the throttle body haha
Here’s my issue. the car has thrown just about every possible throttle code you can have. p1120, p1121, p1515, p1516 etc etc. at this point i have replaced just about every piece in this car that has anything to do with the throttle system. as many of you know, once any of these codes pop up, the car will go into “reduced engine power” mode. the issue with my code is that it is extremely intermittent and random when it happens. the code has popped up on idle immediately after start up, on the freeway, just driving normally, and driving the car hard. i have had to pull off to the side of the road way more times than i could possibly count to clear the code with my obd scanner.
the first part i replaced was the tps (throttle position sensor), located on the right side of the throttle body. that did not fix it. after that i checked the pins that ran into the connector for the tps, in order to check for any sort of damage or missed contact points. it all was mint. i cleaned all the grounds that had anything to do with the cars engine and basic engine computers. i assumed this would be the issue bc that’s the only bit of help and information people know to offer when it comes to electronic issues on a c5. it did not fix it. every inch of cable running from the throttle pedal to the tac module and from the tac module to the throttle body has been checked. i looked for possible corrosion on the tac module and the wiring harness (sitting under the battery) for possible damage. there WAS corrosion from a past owners leaky battery, but no actual damage to components. i replaced the tac module itself, and it’s still not fixed. really the only piece left to replace on this car is the throttle actuator itself but i inspected it and it looked fine (gears were all mint and the pins and connections were too. i also hooked up a scanner that would read how much the throttle body was open and it passed my little test just fine)
at this point i’m really not sure what to do. the car hasn’t ran normally since when i first bought it about half a year ago and it’s the only issue this car has actually ever had.
anyone have any ideas on what to possibly do? thanks for reading!
and yes i cleaned the throttle body haha
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,643
Likes: 4,082
From: Cape Coral, Florida
Jeremiah, WELCOME to the Forum !!…what are you looking at with your scan tool ??…TPS and APP voltages ??…that what you need to look at and it helps if you had a scan tool that can graph these voltages…a lab scope would be best because it will see any voltage fluctuations that may set a DTC…a visual inspection is not how we diagnose these issues…you need to get a DVOM and check the power and grounds on the TAC Module, APP, TPS sensor and TAC Motor and also the 5 volt references on these circuits !!…I don’t know how skilled you are with a DVOM and electrical circuits but that will have to be accomplished first.
Safety Car
Joined: Aug 2011
Posts: 4,450
Likes: 410
From: Portland OR
There is a ground splice pack under the battery tray. Did you take that apart and look at the connections? That will also get corroded from a leaky battery.
I know there are photos of that somewhere on the forum here.
REP usually causes a myriad of codes. The trick is to figure out which one trips first.
Really fancy scanners, I’m thinking like the high buck SnapOn tool, will record the data stream and allow you to step back through the data and find that point.
Of course you would need to have one and have it logging every time you drive it. Not a trivial task.
GM didn’t do the best job on many of these connectors. I would look closely at the female pins on all of them. Bill Curlee has posts about this.
The problem is solvable.
I know there are photos of that somewhere on the forum here.
REP usually causes a myriad of codes. The trick is to figure out which one trips first.
Really fancy scanners, I’m thinking like the high buck SnapOn tool, will record the data stream and allow you to step back through the data and find that point.
Of course you would need to have one and have it logging every time you drive it. Not a trivial task.
GM didn’t do the best job on many of these connectors. I would look closely at the female pins on all of them. Bill Curlee has posts about this.
The problem is solvable.
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
If you are also getting a P1514 code as well------ EFILIVE recommends to ADD about 35% to the "ETC PREDICTED AIRFLOW TABLE " (EFILIVE table C6101) In the diagnostic section under ETC
I see this many times on mid or highly modded engines---Same thing on my own personal 98
This tuning change fixed it and also got the Reduce Power message to go away----
I see this many times on mid or highly modded engines---Same thing on my own personal 98
This tuning change fixed it and also got the Reduce Power message to go away----
