Reduced engine power
Thread Starter
Heel & Toe
Joined: Apr 2019
Posts: 21
Likes: 1
Reduced engine power
I am wondering if it is possible to have reduced engine power without any codes being thrown. I have reduced engine power after a ls3 swap in my c5 and I dont have any codes. I have no idea where to start to diagnose this and fix the problem. The car cranks and idles fine but I only have a vary slight movement with the throttle blade when the throttle is depressed.
Drifting
Joined: Jul 2015
Posts: 1,844
Likes: 375
From: San Jose, CA
No codes and no warnings?
Have you checked ALL the voltages at the throttle pedal (accelerator pedal position sensor / APP sensor), the throttle actuator, and the throttle position sensor / TPS?
Have you checked ALL the voltages at the throttle pedal (accelerator pedal position sensor / APP sensor), the throttle actuator, and the throttle position sensor / TPS?
Thread Starter
Heel & Toe
Joined: Apr 2019
Posts: 21
Likes: 1
Yes spent about 6 hours checking every wire all the way from the throttle to the throttle body. I was wondering maybe if a code could be turned off in the pcm and it is not showing. No codes or warnings anywhere to be found with a tech 2 or DIC. I wasnt sure maybe if something was missed when putting the new engine in. Is it even possible for the car to go into reduced engine power and not show any codes?
Racer
Joined: Jun 2004
Posts: 270
Likes: 67
From: Montana
Might be wrong throttle body... or if you using LS3 TB might need to adjust throttle position vs rpm table...
see this
https://www.corvetteforum.com/forums...y-on-a-c5.html
see this
https://www.corvetteforum.com/forums...y-on-a-c5.html
Instructor
Joined: Jan 2012
Posts: 241
Likes: 28
From: Bel Air Maryland
Does the car have a good alignment since the swap? Only reason I ask is because I just went through this problem with the reduced power mode. My alignment was off because of the rack being removed for the blower install. It caused the steering wheel position sensor to be off enough to throw it into RPM. New alignment fixed it completely.
Thread Starter
Heel & Toe
Joined: Apr 2019
Posts: 21
Likes: 1
After being away for a while I brought the car back closer to home. I was able to pull some codes now. I have these codes. P0102h p0108c p0155c p1637h p1638hc. I know the h stands for history and the c stands for current. Any help as what I should start on? I am thinking maybe the 0108 code is causing rep mode? From what I have found this needs to be addressed in the tune with adding a 102mm tb. Will any of these other codes cause rep mode even before the engine is started?
Last edited by Bigmike0912; Apr 22, 2019 at 03:58 PM. Reason: Added important info
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
P0102 is the MAF Low Frequency DTC & P0108 is a MAP circuit high. I would start by fixing both of those. MAP circuit high means that the circuit is usually open..
BC
BC
Thread Starter
Heel & Toe
Joined: Apr 2019
Posts: 21
Likes: 1
0102 code is a history code and i'm thinking it happened before the car was changed to speed density which I forgot the mention. The 0108 code seems to be the one I should work on first. Any tips on what to do with this?
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Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Find the MAP sensor and see if you have 5 VDC on one wire The other wire is the signal wire out of the sensor.
Check the wires at the connector and make sure that they are not broken / damaged. Look at the FEMALE pins inside the connector and make sure that they are not spread apart or corroded.
Unless the MAP sensor was relocated, it behind the manifold. They are very tight on the FAST 102 and can get damaged.
Clear ALL the DTCs and see what comes back
BC
Check the wires at the connector and make sure that they are not broken / damaged. Look at the FEMALE pins inside the connector and make sure that they are not spread apart or corroded.
Unless the MAP sensor was relocated, it behind the manifold. They are very tight on the FAST 102 and can get damaged.
Clear ALL the DTCs and see what comes back
BC
