Code 1518?

[2Fbodcru]

Hey guys,
I have gotten a "1518" trouble code on my 99 Camaro. That code is in neither of the two books that I have, and I haven't been able to find it on the internet or the search of the forum. If anyone can tell me what this code is, I would appreciate it very much.

Thanks in advance,
Bruce

[Injuneer]

Searching on "GM P1581" I found this reference:

http://service.gm.com/gmspo/mode6/pd.../2001file7.pdf

It lists P1581 as "Indicates that the serial data line between the PCM and the TACM has intermittently or continuously failed."

I suspect that relates to the traction control module but not sure.

I also found a generic list of codes that showed this:

P1518 - Intake Manifold Runner Control fault - Stuck Open.

...but that doesn't make much sense.

What engine do you have?

[2Fbodcru]

Hey Injuneer,
I have the standard 6 cyl. 5 speed

[2Fbodcru]

Some background:

Friday evening, I got in the car, backed out and began to drive a little ways, and all of a sudden, it felt like it was about to die on me. I had a light come on that said "Reduced engine power", and then the "Service engine Soon" light came on. I pulled back in, and went and got my code reader, "Creader" brand, and checked it, and that 1518 code was what I got. When I had gone out there to crank it the first time, it turned over and over, before it finally cranked up. I have had probelms with it running a little rough for a little while now, but It actually had started running better for the last couple of weeks. It has about 108,000 miles on it BTW. It will crank, but it takes a few turns to get it going, then it just doesn't have any power

[2Fbodcru]

Well, I got this crazy thought to go and clear the code with the "Creader", and then disconnect the battery for about 30 minutes, while I did something else. I then hooked up the battery again, and cranked it and drove down the street and back. I haven't given it a full test drive yet, but so far - its cranking and running

[Christopherrr]

3.8 F-bodies had electric TB's...have you had surges in power or lack there of? From what I've heard, they tend to go out due to heat and wear.

[2Fbodcru]

Up until now, mostly a little bit of a rough idle, and some loss of power, but I switched gas stations and it seems to help - so far.

3.8 F-bodies had electric TB's...have you had surges in power or lack there of? From what I've heard, they tend to go out due to heat and wear.

[fastTa]

To the best of my knowledge, only Ford's used the IMRC butterfly valves. It's not all that uncommon for code readers to misinterpret the actual numerical code, but I have seen some reference to P1518 being somehow related to the ETC (electronic throttle control) system not functioning properly and/or low battery voltage.

DTC P1518 Electronic Throttle Module to PCM Communication or

DTC P1518 Throttle Actuator Control (TAC) Module Serial Data Circuit (Alldata)

5 bucks says you have a low battery.

I had to work on a late model V6 f-body (can't recall the exact year) that had that same exact code. After talking with Lethal Performance in SA, they said that low system voltage could trigger that code because it is critical that the ETC system that controls the TB receives a specific minimum voltage.

We tested the battery found it was not up to par. Installed a new alternator and battery and no more rough idle or P1518.

[2Fbodcru]

Hmm, interesting, that’s good to know. The battery is not that old, but that doesn’t mean anything.
I think that I am going to print this info and keep it on file, just in case.

Thanks,
Bruce

To the best of my knowledge, only Ford's used the IMRC butterfly valves. It's not all that uncommon for code readers to misinterpret the actual numerical code, but I have seen some reference to P1518 being somehow related to the ETC (electronic throttle control) system not functioning properly and/or low battery voltage.

DTC P1518 Electronic Throttle Module to PCM Communication or

DTC P1518 Throttle Actuator Control (TAC) Module Serial Data Circuit (Alldata)

5 bucks says you have a low battery.

I had to work on a late model V6 f-body (can't recall the exact year) that had that same exact code. After talking with Lethal Performance in SA, they said that low system voltage could trigger that code because it is critical that the ETC system that controls the TB receives a specific minimum voltage.

We tested the battery found it was not up to par. Installed a new alternator and battery and no more rough idle or P1518.

[2Fbodcru]

Well, since I first posted this, my car has cranked and run good for a while, and then it will start messing up again - on and off. I haven’t been able to get the code checked anywhere else until this morning, because I would always have to clear the code to be able drive it. This morning I had trouble cranking it, but finally got it cranked, and was finally able to drive it with the SES light on. I took it to Advance Auto Parts, and the guy that checked it didn’t really seem to know what he was doing, but he did get the same P1518 code that I keep getting. His computer readout was this:

History DTC P1518
TAC System
To PCM Commun.
Serial Comm link
MIL REQUESTED
Since IGN PASS
Since Clear P/F

He said that it was most likely either a crankcase position sensor, or oxygen sensor, so I don‘t know.

I then went across the street to Auto Zone, and this guy seemed to know a little more than the other guy. He checked it, and on the readout, it was a code P1518 again, and it also said TPS control something or another, but his computer inside the store said that the P1518 code for a 99 Camaro, 3.8 engine, was “Intake Manifold Runner control fault (Stuck open)” - same as what you got Injuneer. Both suggested that I go to someone with a more sophisticated diagnostic machine and have it thoroughly checked. I wanted a third opinion before spending the money to get a professional to check it, because I have not had much luck with the professionals either. I left Auto Zone and headed for O’Reilly Auto Parts (which is also across the street from Advance Auto), and now my light was off, so I couldn’t get it checked. It was also running fine, except for that ever present slightly rough idle that it has had for the past 2 years. About a year and a half ago, I had new OEM plugs and wires put in and later on, I put three new OEM coils on the car. The idle stayed the same. Last week and yesterday, I had the battery and alternator checked, so they were checked twice, and both were showing that they were good.

Anyway, I just thought that I would add some history to this thread, in case someone else runs into similar problems and does a search, and also in case someone has any more ideas. Most likely, if the light comes back on again, and I can drive it to O’Reilly, I am going to see if they can check it and give their opinion on it. Then if I can‘t solve it after that, I may have to give in and take it to a mechanic.
If anyone has any ideas, I would be very interested.

Thanks,
Bruce

[Injuneer]

Kevin already told you what it was.... apparently your engine was a "fly by wire" throttle. There is no cable between the accel pedal and the throttle blades. There's a position sensor under the pedal, and that goes to the PCM. Then the PCM tells the throttle acutator how far to open. At some point, there are several things that need to be taken into consideration and integrated to get the correct throttle position, since the electronic throttle is also interfaced to the idle control system and the traction control system.

Just because the SES light went off doesn't mean you couldn't have had it scanned at O'Reilly.... once the light comes on, the code is stored in the PCM and can be obtained even though the SES light went off.

You need to verify your engine has the "no cable" electronic throttle control, and if it does, you need to have it checked for problems. The Corvettes have that system, the V8 in my 2001 Silverado has that system.... apparently its use is fairly widespread.

[2Fbodcru]

Kevin already told you what it was.... apparently your engine was a "fly by wire" throttle. There is no cable between the accel pedal and the throttle blades. There's a position sensor under the pedal, and that goes to the PCM. Then the PCM tells the throttle acutator how far to open. At some point, there are several things that need to be taken into consideration and integrated to get the correct throttle position, since the electronic throttle is also interfaced to the idle control system and the traction control system.

Just because the SES light went off doesn't mean you couldn't have had it scanned at O'Reilly.... once the light comes on, the code is stored in the PCM and can be obtained even though the SES light went off.

You need to verify your engine has the "no cable" electronic throttle control, and if it does, you need to have it checked for problems. The Corvettes have that system, the V8 in my 2001 Silverado has that system.... apparently its use is fairly widespread.

My mistake, I thought that Kevin's final conclusion was that I had a low battery: "5 bucks says you have a low battery". As far as the deal with the light, I thought that it could be checked as well, being that the computer stores codes, but every time I have run into these situations, I keep getting "I can't check it if the light isn't on". I am not going to argue with someone who is willing to check my car for free.
It does have the "no cable" electronic throttle control.

[fastTa]

My mistake, I thought that Kevin's final conclusion was that I had a low battery: "5 bucks says you have a low battery". As far as the deal with the light, I thought that it could be checked as well, being that the computer stores codes, but every time I have run into these situations, I keep getting "I can't check it if the light isn't on". I am not going to argue with someone who is willing to check my car for free.
It does have the "no cable" electronic throttle control.

Well what I was just trying to get across by saying "5 bucks says you have a low battery" was that checking the system voltage and battery condition would be a good place to start in order to possibly rule out something simple.

I gave you the two interpretations of the codes straight from Alldata. Somewhere along the circuit of your TAC module circuit, you have a problem that is causing the PCM to set a code.

That's where you need to start your diagnosis.

[2Fbodcru]

Well what I was just trying to get across by saying "5 bucks says you have a low battery" was that checking the system voltage and battery condition would be a good place to start in order to possibly rule out something simple.

I gave you the two interpretations of the codes straight from Alldata. Somewhere along the circuit of your TAC module circuit, you have a problem that is causing the PCM to set a code.

That's where you need to start your diagnosis.

The low voltage suggestion actually made sense. I thought that maybe my alternator was intermittently failing and causing my battery to loose charge, etc. Although, I had the battery and alternator checked twice, and they both checked good both times. What you said about the fact that it was “not uncommon for code readers to misinterpret the actual numerical code”, also made sense. So, finally I was able to drive it this morning after it set the code, and I took it to the two auto parts stores to get it checked to see if they got the same code and to find out what their suggestions were before I started to spend money on the car. Both stores did get the 1518 code, so now I can go from there. The car is running fine now though, so I guess I’ll see how it goes.
Anyway, I appreciate all of the advice.