Intermittent SES Light

[c4zr1]

Well I thought I had my problem solved, but need some help. I did the AB pin jumper and getting codes 34, 44, and 54. I can drive the car about 5 miles and the SES light will go off and the secondaries start working. By the time I get back home after 10 or 15 miles the SES light comes back on.
I have checked and the vacuum pump and lines holds pressure, I changed the MAP sensor out. By the way I sent my ECM off to Tom Henry Chev. and had it rebuilt as well.
I wish I had a Mark or Cory close by, but I am way up in the Texas Panhandle and there does not appear to be anyone that knows anything about ZR-1's close by. If I have to I will load it up and take it to Mark or Cory, but I thought I would try solving the problem myself if I can.
Do I nned to invest in a Tech 1?
Any help will be appreciated.

Thanks!
Don

[Kevin]

well i wouldn't have sent anything to tom henry chevy. he doesn't really care about zr-1 owners. perhaps you have an o2 sensor going bad

[John Boothby]

Amarillo? I had to join the club and pay a buck to get a beer there with my meal! Not used to dry counties.

I am assuming you have a FSM? You have 3 different issues. 34=MAP sensor; 44 =O2 sensor and 54=Fuel pump. Were all your codes cleared when you installed the rebuilt ECM?

Sometimes the MAP sensor vac line can come loose. I tie-wrapped mine. Make sure your elec connections are tight. Or it could be a bad sensor. Wouldn't be the first time a defective part came off the shelf. Also, check all your pcv lines and connections.

A Tech-1A would help with the O2 and fuel pump volts. I have not had any problems with mine, so I have no experience with those.

Tech -1A's can be had for around $150-300 on fleabay from time to time. Be sure you get the correct modules. I havn't checked lately.

[c4zr1]

I do have the FSM's I will try and replace the 02's. Should I go with Delco or can AutoZone fix me up?
Thanks for the help John!

Kevin,
Tom Henry Chev treated me very well so I cannot say they did not take care of me for my ZR-1 needs.

[John Boothby]

Just follow the diagnosic charts in the FSM. I have used them before I broke down and bought the Tech-1A, and it worked pretty well. Just easier with the scanner.

I don't know about the 02's, someone else will have to advise you on that. I don't see why Autozone shouldn't be able to fix you up though.

Tom Henry Chev has always done right by me.

[tomtom72]

fwiw on the O2 sensors.....our OE ones are Bosch and autozone sells Bosch. the Bosch are a lot more money than the house brand. I bought the Bosch when I changed both of mine as I felt it might be a smarter choice?

My take on the codes: fwiw:o

34 = low signal voltage, high vacuum. possible oil clogging the MAP hose or the MAP hose is collapsing under high vacuum conditions. Or the MAP could be giving up.

44 = left O2 says that bank is lean. bad sensor or fuel filter clogged a bit or pumps are getting tired. This could tie into the DTC34.

54 = low voltage fuel pump. This code is used to detect a faulty fuel pump relay. Also the connection at the ECM could be faulty.

:cheers:
Tom

[Kevin]

i'm glad you guys had better luck with Tom then I did when they sprayed orange clean on my motor then washed it down...the parts guys have always been top notch though. body shop is great too

[scottfab]

Well I thought I had my problem solved, but need some help. I did the AB pin jumper and getting codes 34, 44, and 54. I can drive the car about 5 miles and the SES light will go off and the secondaries start working. By the time I get back home after 10 or 15 miles the SES light comes back on.


Sure does sound exactly like what I saw when the secondary fuel pump stated failing intermittently. All was fine for the first few WOTs but just like when the vacuum pump works at 50% when an extended WOT happens the 42 gets set.
I eventually attached a pressure gauge and routed it up to the windshield so I could see it drop during the WOT. It dropped to 44 when the code set. A good secondary pump keeps it at 50 or so.
Good luck

[c4zr1]

I went to the local O'Reilleys and asked if they would put their scanner on my car.
Codes:
DTC-23 Manifold Air Temperature Sensor
DTC-35 Disconnected Manifold Pressure Hosw
DTC-46 Fuel Enabilar Failure
DTC-62 Oil Temperature High
I replaced the Manifold Air Temperature Sensor and the MAP Sensor
Took the car out for a spin. Still SES light. After about 5 miles the SES light went out I turned the Power Key on and the secondaries come alive for about a minute. The ses light come back on and stayed on all the way back home.
I rechecked the vacuum lines to the vacum pump and toward the plenum and it held vacuum ok.
Very Frustrated. I think it is time to take it to a shop.

[c4zr1]

Well I went back out to the garage and read through the Service Manual and found the section to read and clear the ccm and ecm codes. I went all through it. What was strange there were no codes in either that displayed.
I did discover a strange noise coming from under the plenum. It sounds like a ticking sound. Either a shorted spark plug wire sound or like a gasket blowby leak. I can hear it louder from the driver side top left side backend of the plenum. It does sound like it is under the plenum.
What do the experts think the sound is?
Thanks for your help!
Don

[VetteMed]

Injectors can tick, especially if stuck...

[tomtom72]

The area you say the "tick" is coming from is where the coil rack is located, and quite a few other electrical connections as the DIS box connections are also in the same location.

Andrew is also correct in that the pintel type injectors do make a distinct "ticking" noise sort of like what solid lifter old school small block chevys used to sound like at idle.

I'm puzzled by the different set of DTC's that autozone retrieved. Or maybe I missed something here?:o

we don't have a DTC 35 in the LT5 library? The rest are consistent with what you listed in the original post.

I know this isn't much diagnostic help. I just wanted to post a response to you so that you would not think no one is listening. Let me go back to the FSM and I'll post up after I think about this a bit! I hope Dom or Pete see this and post up.....that's better than me doing this!

:cheers:
Tom

[tomtom72]

Okay:

23 = low intake air temp. will set if no VSS signal but motor running more than 2 minutes. Or ignition on motor off ( as in just scanning for stored DTC ) coolant temps greater than 86* Check the connection at IAT & ECM is my best guess or bad wiring.

35 = doesn't exist for an LT5

46 = VATS system fault. I don't get this one. It seems that two way serial data communication between the CCM & ECM is snafued some where, wiring issue or ground issue most likely as you have the correct key.

62 = oil temp above 286* try resetting the oil life monitor is what I get out of the diagnostic aids. It's that or the wiring is snafued again!

Something strange going on here. Not much of these DTC's make any sense. Unless the ECM is out to lunch? You don't have access to a know good ECM just to swap in to see what happens with all these DTC's?

Don, you don't have your own scanner, right? Throwing parts at this issue is not a good idea. Do you know anyone that is near you that has a scanner with our software so you can do the scan. Do you have a fuel pressure gauge? I'd do the F/P test just to eliminate that side of this equation one way or the other. After that I'd move on to ignition, then finally to start checking all the wiring at the indicated malfunctioning sensors. Sorry man that's all I can come up with, not much I know!:o

:cheers:
Tom

[c4zr1]

I do not have my own scanner. Thinking about buying one though. I do have a pretty repupable shop I take other stuff too. When you say someone with a scanner with our software. What does that mean? What should I ask the shop guy about what software he has? I can probably come up with the Fuel Pressure switch to check the FP's out.
I do appreciate the feedback from everyone up to this point.
On my ECM I did get it rebuilt, but I may have someone here in town I can borrow a 91 ECM from.

Thanks!
Don

[ScottZ95ZR1]

IOn my ECM I did get it rebuilt, but I may have someone here in town I can borrow a 91 ECM from.

Thanks!
Don

Hi Don!

While your ECM was out for rebuild you had my spare. Did you drive the car enough then to be confident it fixed your issues - I mean are the issues you're seeing since swapping back to your rebuilt computer the same as before ?

[scottfab]

I think you'll find having your own scanner to be $ well spent.

[c4zr1]

Hi Scott!

I does seem to have the same issues as before. I drove the car very little while I had your ecm. I probably did not drive it enough to really know it was the ecm like I thought. The ecm might not have been the real problem.

Don

[ScottZ95ZR1]

Hi Scott!

I does seem to have the same issues as before. I drove the car very little while I had your ecm. I probably did not drive it enough to really know it was the ecm like I thought. The ecm might not have been the real problem.

Don

I ask only because I recall reading at least one thread where someone had their ECM remanufactured to find it was still faulty. Hopefully that is not the case here.

I know Marc Haibeck has had success having them repaired - hopefully by the same company Tom Henry sent yours to. Best of luck to you. :cheers:

[tomtom72]

Don, Okay on this scanner thing, I would agree with Scott Fabre as it's the second best money I ever spent on my tool collection. A Tech1A is the schizzel but you need all the software so you can run all the functional tests in the FSM. The Master Tech would be the tits, but again you need OBDI / LT5 software suite to be effective.

I have an antique snap-on MT2500 with GM OBDI software package for power trains & ABS systems. However it will not do the functional tests in the FSM. But, it's better than relying on purely "generic" OBDI software as it gives me the complete LT5 library of DTC's as listed in the FSM....no translation needed.

I am sticking to the first set of DTC's you posted and my original first guess. Check the fuel pres at high engine load & high rpm. You proly had some oil in the MAP hose or sensor or both and the new MAP solved that issue. Make sure annually you clean the PCV valves. The lean O2 and the the DTC I said were related make sense if fuel starvation is an issue.

Also, when using someone's ECM, a 90 can use any year ECM with a 90 PROM, and you have to drive it enough to let it learn the car & your driving habits. That takes about 30 minutes at the least under varying conditions. They actually learn how you drive the car and adjust to it, but it takes time. Unless things have changed, the guy Gordon told me to call said the issue is that LT5 ECM's are unique. As of two years ago GM has not let anyone see the schematics and with out those ya can't fix much! It's not the parts, but the circuit diagrams that count. Maybe that has changed, but the guy told me that most places that say they can fix an LT5 ECM are using the L98/LT1/4 diagrams and extrapolating. After all they are all OBDI ECM's except for the LT4 ECM. I wonder if the MCN has those schematics on file? I still have my Minox! LOL

:cheers:
Tom

[c4zr1]

Tom,

Thanks for the feedback!
Where is the best place to order a Scanner that has the LT-5 software with it?

Thanks!
Don

[72ZR1]

vettemed has one for sale in Z-R1 parts for sale.

[tomtom72]

Tom,

Thanks for the feedback!
Where is the best place to order a Scanner that has the LT-5 software with it?

Thanks!
Don

:o I wish I could answer that question. Also, sorry for taking this long to answer you Don. Things have been a bit hectic at work. I think Bosch now holds the rights to the Tech series of GM scanners. I bought mine off of E-bay, used naturally, and I hunt the listings for software to fill out my library. New these things cost a fortune! Oh yes there are less expensive units, but then there is the software issue. Not all have paid 'use licensing fees' so you have to be careful on that aspect as it's the software that makes a scanner useful. Eventually I may just bite the bullet & flag down the snap on guy and buy/order the software I need..body control module & FX3 software would be nice!

You pulled the DTC's you listed in your first post, right? You used the paper clip method? I think I should review them and my diagnostic thought process so I may be more helpful to you. I'll do just that and report back later today!
:cheers:
Tom

[c4zr1]

Well very interesting find. Non of the sensors was causing my problem or a vacuum leak. I was able to borrow a ecm from a friend and put my prom in it. Now no SES light and all seems to be working right. The secondaries are coming on and it is running good. My ecm was rebuilt less than 6 months ago. May have gotten a bad rebuild. May be sending my ecm off to K&B Special Corvette Parts. I plan on taking the car down to Corey's in June and let him tune it and maybe check the injectors and weld up my corsa exhaust. I am getting short surges at cruising speeds.

Don