Help guys... Multiple Trouble Codes

Kyle F

Addicted to Boost
May 24, 2001
Well, I just got the TTA on the road and am using it temporaily as a daily driver, the only problem is that is is throwing all kinds of codes.

First the thrmostat hung open and was't going into closed loop, so we replaced it hoping that would cure our poor gas milage problem (about 19mpg on the highway), but it helped a little, but not fully.

It has been getting an unusual amount of knock at just 3/4 throttle and aroun 12psi, so first we tried to up the fuel pressure, but when it got near 49psi without the Vac. line on.. I said that cant be right and we set it back to 45PSI and took two rounds out of the ajustable wastegate. This shoudl lower the boost 2psi.

So, after this, I hooked up turbo link for a long drive to see what was going on. Every now and then I noticed it would flas a trouble code but the SES light on the dash would not come on and I couldn't get the to F1 key fast enought to catch it, so I did about a lengthy log and saved it to look at later.

So, I get home and as I am going through ti all the numbers look about right. Going from rich to lean, all # within spec, and in closed loop. Every once in a while an code was set, I got codes for the EGR, Water Injection, TPS, MAT, ESC, Code 52(Checksum) etc etc. :mad:

So, my questions are, is my thrasher bad? Is something not connected? Why doesn't any of the codes stick around? Is the ECM bad? :confused:

I had the computer take a dump on me in the past, but its not acting anythign like that thsi time. :(
When I get these types of problems, the first thing I do is tap on all of the fuses and see if any are intermittent. Not unusual.

Are the mass, TPS, MAT etc. on the same circuit? I don't believe they are (I could look I guess).

I've never blown a 748 but I guess you could have another one bad. I suspect the ECM last though.

There is a 100mS CE lamp delay. That fast enough that it sounds like you have ECM losing it's brains for a split second rather than real codes.

Is there any sign your +12V is kicking out or the alternator is extremely noisy?
Yup, everything else is fine. Shows good voltage all the time on the dash and in turbolink. I guess I am going to swap the chips and see what happens. Back to slow spooling. LOL.

Any other ideas?
Nope.. Had a bad coil pack, changed it... Nothing. Ignition module checked out OK. Got new plug wires to replace factory one. Nothing happend. Got new plug because one was fauled on the bad coil, and the rest had been run pretty rich. Therefore, I got a new O2 Sensor because I felt I might be running too rich and not getting enough cross counts.

Still same problem.

I now hate the car and want to rid myself of it.

I hate it I hate it I hate it.

If its not the ECM the car will go. I do not have the time nor money to invest in a a major repair.

I will go buy myself a freaking Normal Tans Am and put a carbed 350 in it where getting 400hp is easy and no stupid Computer worries.
Originally posted by terryk

I've never blown a 748 but I guess you could have another one bad. I suspect the ECM last though.

Ya but we're talking 7148s here <G>.
But, you knew that <G>.

What codes are you setting?.
When fixing codes start with the highest value ones first. There is a reason for the order they're in.

I'd look for a bad ground first, and as Terry Mentioned, a alternator with a shorted output diode can really put spikes into the electrical system.
Ditto on that, ruce. I would be checking all of my grounds. Most notably the one at the back of the heads, bell housing. Clean and re-tighten.
This is an odd problem with codes coming out in all different ways. Even water injection. All the ground have be checked and sanded to assure good contact. SOmetimes its one code, other times its multiple. Everytime its multiple, they are just in numerical order.

Would a shortened diode cause KNock at 14psi in my car?