Some suggestions please. I was just driving normally and exiting a highway and the car went in to reduced power mode. First time this ever happened. I have searched but it seems that normally there is a code and / or other messages in the dic. I get no messages, no codes, and no check engine light. I limped home, did some reading and when I restarted the car, it seems fine. It just happens I was logging at the time it happened and I see absolutely nothing out of the ordinary. I really don't even know where to start looking for the problem.

I read that restarting the car 3 times resets the REPM... does anyone know if this is right, or is it just coincidence. I tried restarts when it first happened, but it was still in REPM then. I think I tried twice, at that time.

 

When that happened to me it was throttle body related between the pedal and throttle body sensor. It started happening more frequently as time passed until I replaced the both pieces. Probably didn't need to do throttle body but I decided to upgrade to a ported polished unit anyway.

 

2 times I've encountered this. The first was back when the car was completely stock. Never had a code. Different pedals and throttle body. I was able to recover both times by disconnecting the battery.

 

No codes at all?

 

No codes at all. Not even CE light. I went for a little drive again and it didn't come back, but a little nervous about going to far for now.

 

I fought this headache for years at first it would happen randomly and seemed to be more pridominat when I would sit at a red light on a hot day and go to take off then boom R.E.P.
Service active handling.... I did everything from clean grounds to checking my main fuse box connection.... it drove me bat #@$! Crazy. Then towards the end it would do it almost every time I would drive it. So I replaced my throttle pedal because I already had a tpis 102 throttle body and didn't want to buy another 600 dollar throttle body after this one was only a year or 2 old. I even had my tuner try and alter the tune to get it to stop.... finally I bought a NW 102. Put it on and haven't had a problem since.

What sends your car into reduced engine power is the ecm demanding a percent open on the throttle body and the throttle position sensor telling the ecm that the percent demanded isn't the actual position of the throttle body. So to keep from having a wide open throttle (worse case) condition. The computer cuts fuel and limits spark.


You can cut the car off, open the driver door, close it back, wait 1 minute and start the car back and it will come out of reduced engine power unless you have a short or bad throttle body ect.

 

Aren't there codes though for TPS not matching what it should?

Are any codes turned off that could be the problem?

 

I drove the car for a while tonight and nothing. If it comes back and I cant find anything obvious I will change the sensor at the pedal... or the pedal if they come together.
I didn't think about opening the door. That's probably why it cleared when I restarted at home, but not while on the road.


I thought about that and nothing is turned off other than O2 stuff, that I can see.

 

Well, I drove the car for over an hours this morning...... highway, city... all over the place doing some Maf tuning. Nothing..... car ran great.

Then I come home for an hour, and leave to go out again and boom... a block from my house.... reduced power mode. No codes.

I started digging and looking over the tune again. I noticed my P0068 settings are basically stock. I've read that this can be an issue on blown cars, but is it possible to cause an issue and not throw a code ??

I dunno, frustrating little bug. Other then that this car runs as good as any I have ever driven. Even the temperatures are impressing me so far with my homemade shroud mods. I have to figure this out. Any more ideas appreciated.

 

My old car had a similar issue. Turned out, it was the thermostat opening too much too soon. The ECT would come down too fast and/or too low and the PCM would interpret that to mean that something was wrong with the ECT system/sensor. It was cured by replacing the Mr Gasket 160 degree 'stat with one from Lingenfelter. Figures that a Corvette wouldn't like a cheap 'stat. Once I paid double for the Lingenfelter 'stat, she was good.

Hope your trouble is that simple to fix!

 

I actually did have problems with that code the first time I got on it after putting the SC on. After it happened I couldn't get the car to go over some stupid slow speed or over a certain throttle position. I didn't realize that was called "reduced power mode" so I didn't even think to post about it.

But on mine it DID throw a code, so I'm not sure if it's that or not.

You could always loosen the settings way way up and see what happens

 

I had this happening in my S/C 05'. I unplugged the throttle body cleaned the pins and plug with electrical cleaner. Put some Dielectric Grease on the connector, plugged it back in and haven't had an issue in about two years. If you decide to do this, be careful with the clip on the throttle body/plug. It will be very easy to break it.

 

All input appreciated. I am going to rule this out for now because it is the same thermostat I have been running for a long time and the ECT is normal in all respects in my logs.

 

Good point for sure. The first thing I did was check all connection including the TB. All clean and tight so I don't think that's it.

 

Update..

First thanks to everyone for advice and suggestions. It turned out that there were some codes shut off in the tune. Only way this could have happened is the first person to every tune the car must have shut them down. The 5 years after that of constant mods and tuning, was started from that tune. No reason why a tuner would do that.

After turning a bunch of codes back on, I got the REP and a P2135 code which led me to the throttle body. With some checking I found that one of the wires I had extended was not a perfect connection. I hardly can believe that caused an issue, but its seems to be ok now after redoing the connection. Shows how temperamental these cars are. Make sure all connections are PERFECT.
Anyways, with all the work we did, that is the only problem that has crept up so far, and I would say that is more than anyone could ask for. Car is running perfect.

 

Glad you got it figured out

Someone did a good job if that's the only issue you've had

 

Yeah thanks... Its kind of weird. I cant believe it myself and keep waiting for something to happen. Car hasn't even been back to the shop once. Best of all it was the first warm day here (86 roughly) and the she never got over 195, even in traffic.

 

That's really good. What radiator are you running?

My fans aren't set to really do a whole lot until right around 200, and so far they've been able to keep it 205 or less but I bet that will change once we get some real heat. Original radiator here. At some point I need to make some little side shield things to box in the intercooler to keep air going through it decently

 

I have dewitts rad and dual fans. I also kept the stock shroud (modified obviously) which I think helps a lot. I set the fans to come on quite early. They are there, I might as well use them.

 

I've seen this too many times.

Always, always compare the tune from your car/pcm to the stock one before doing ANY tuning by yourself.

The trick is of course to have something to compare and pro shops can easily do this, since they build new cars among others and have access to stock tunes. Tech II is another option. And HPT repository does this as well, as long as you make sure there's enough identical stock tunes..