Decided to take the 98 out for a drive on Thursday. An emissions inspection is due on 28 Jan and I wanted to make sure that it was running good. It was difficult to get it to start. The engine would turn over fine but would not fire. After a couple trys it started. Everything was going GREAT and then, out of nowhere the engine cut off like it ran out of fuel! Had a 1/4 tank so I figured that it could be empty. Added 1 gallon of fuel and she started right up. I also had more DIC messages than I have time to list. I filled it up and the gas gauge was correct at 1/4 tank.
Approx 1 mile from the filling station it died again. This time I get "service engine soon", Reduced engine power, ect, ect!!! I turned the ignition key 5-6 times in short burst to save the battery and it started again! Got it back to the gas station and it died again. This time when I started it, I got all of the same DIC messages! I checked for DIC codes and I had a VERY LARGE list! The killer one was PCM "NO COMMUNICATIONS" :eek: :eek: :eek: WTF does that mean???

I removed the PCM and everything looked good! Hooked it back up, tried to start it and ZIP, NOTA, NOTHING. She turns over but the fuel pumps dont run she wont fire and now I'm LOST!
I can get it to start and run but I am running the risk of getting stranded!

I did figure this out; If I turn the ignition key in short rapid burst (5-6 times) it will start and run during this procedure! It runs fine but eventually it will spit, sputter and die sometime, somewhere down the road. I have run it to red line when it runs and it does not miss a beat.

Could the ignition electrical switch cause this??? I get the "Pull key wait 10 sec" a lot. The part is $70 but I hate to easter egg. What does PCM "NO COMMUNICATIONS" mean and what could cause it?

PLEASE HELP!

Bill Curlee

 

TTT

 

If you connected anything to the 3 wire pigtail for a radar detector, etc. disconnect all the add ons and see if that helps. My '98 wouldn't start because it had a wiring short in the harness under the console, when the console was removed the car started ok; after the harness was unwrapped and retaped the car ran fine. Some early C5s had wiring harness problems which caused all kinds of error codes, don't know if this is your problem but it's one possibility. The dealer had mine for a week before they disconnected the pigtail loads but a week later the problem returned and removing the console let the car start.

 

Battery connection or battery ? :confused:

 

Sounds like a grounding failure or a short. Time to start running the wires.

 

Fast one

The theory about a bad wire in the console area is starting to sound like a dead on hit. My traction control is OFF all of the time without me having to push the button. :crazy: My pig tail is still taped in the origional factory tape, so that is out of the equasion Sounds like I need to start tracing wiring harnesses!

Wolfebros

My battery is fully charged has been in and out 3-4 times over the past few days. The connections were cleaned and are properly torqued on. There is NO signs of leakage or past acid damage. :thumbs:

PLEASE keep the ideas coming. I still do not know why I am not getting COMMS to the PCM.


[Modified by Bill Curlee, 8:05 PM 1/23/2004]


[Modified by Bill Curlee, 8:05 PM 1/23/2004]

 

Have you owned the car since new? If so, and you haven't installed something to keep traction control off, you do have an issue there.

 

I have owned the car since day one! This TC problem happened the same time it went **** up!
BC

 

Was there ever the dreaded battery leak?

Mine had that happen and over a year later, just all of a sudden one day the dash lighted up like a christmas tree. It turned out that the connecters to the comp. under the batter had corroded connectors.

The dealership said they could clean it and it would probably be fine, but since it was under warranty they replaced everthing.

No probs since.

 

Never rule out a broken wire in the harness. I have solved many a mystery electrical issue by slowly flexing the harness along its length. Since you have the trction control light to give a clue have someone whatch it while you work the wiring. Be patient, persistent & be sure you can dismiss one area before moving to the next. Good luck & hang in there, it's fixable! ;)

 

Holy S$%^&*( Bill, you've been the norm poster for awhile now then POW, this out of the blue. I agree on the electrical advice, are you adept at this or not? Typical of used cars to have elec issues, flexing the harness, unplug/replug relays, fittings, etc and re-check.

Water intrusion possible? You said you left it for a bit and then re-started? Humidity change? Have you disconnected then re-connected the batt terminals lately? Unplug the batt totally, charge it, leave for a day, then re-hook up battery?? All guesses based on past car experiences, not C5 specific.

Good luck, hope solution arrives for you.
Smash

 

hey bill,
is it possible it could be the pcm itself?
with everything that is acting up and the loss communication code it's a possibility.
if you know someone with a spare that you could plug into your car would shed some light on the situation.

 

ROCKnROLL
Man I wish I could find a spare PCM. That would take alot out of the equation! I am good at problem solving electrical and mechanical problems but I have SOOOOOOO many symptoms that it is very hard to find a place to start. The PCM is something that I can not rule out.

I've narrowed the following things down.

It's not the battery and it has not leaked acid. It is fully charged and the connections are clean and tight. It has been removed from the car and tested. It will crank the car for a L O N G time before it dies.

It is not a water problem.

The PCM was disconnected and connections inspected. The harness was wiggled, bent and twisted and seems fine.

I can get the car started if I turn the ignition switch in short bursts 5-6 times. When it starts I can clear all of the codes and it will run fine for a while and it will either go into "REDUCED POWER" mode or will die like I shut it off all by it self. If it shuts off by it self, I get the dreaded "PCM NO COMMUNICATIONS code. If it defalts to reduced power I can clear the code and it will run good again. When it does run good I can run it to red line and it has full power and doesnt miss a beat!

I will take the console apart today and see if I can see anything and let you all know what I find.

BC


[Modified by Bill Curlee, 8:41 AM 1/24/2004]

 

My fuel pump problem also caused a PCM communication problem on my '03 LS1. This first made the dealer think there was something wrong with the 'gas module" (near the battery), so they replaced it. But that was not the problem. Now they say the fuel pump is dead (located way up under the car above the gas tank). Don't know how they tested to determine this. So PCM problems may also be caused by something other than electrical.

Mind you, nothing on my car is solved and working yet, so I may not yet have the answer either...

 

Well I gave it hell today and got a little further in figuring out what is wrong! I got it started this morning and it displayed NO problems. I was getting ready to take it to a HEATED GARAGE to remove the console and take a look at as much of the engine and dash wiring as I could. As I was about to leave, it went into "REDUCED POWER" mode and threw a few codes! They were: PCM P1518 H C & TCS C1278 C. I can normaly go into manual diagnosastic mode and clear the 1518 code and the engine will smooth out and run fine. I had to shut it off and restart it numerous times to get it to clear. Once I got it to clear it ran fine all the way to the garage.
It looks like I might have a bad Throttle Actuator Control (TAC) module! I removed the two electrical connectors on the module and the connectors, the wiring harness and module connection pins all were clean and dry! So,, another suspect part is the TAC module!!! :cuss :mad
I did find a chaffed/pinched wire on the cigarete lighter orange wire but I doubt if that had anything to do with my problem. The lighter worked fine!

Where can I find the "Ignition Switch" and circuit in the service manual? I have looked everywhere and do not see it in one place. I see power and wires coming fron it but not the switch.

So there you have it! MY WHOLE DAY! Atleast it was warm in the shop!!! :D It was 11 degrees out today here in Groton CT!:crazy: and is suppose to go down to -4 degrees tonight! :skep: COME ON SPRING!!!!!!

Bill C

 

bill,
in my 98 service manuals volume 1 on page 8-662 describes ignition switch replacement. i don't believe that's what you want but then i found in volume 3 on page 6-377 the starting and charging schematics that shows the ignition switch.
hope this helps.

 

ROCKnROLL

The schematic that you found proved my theory! The ignition switch must have 50 wires going to it and that page only shows one! :mad
The switch must be spread out all over the book. This one is going to be a Bit$& to figure out!
Thanks for helping me find that page! :thumbs:

Bill

 

There was a TSB for '98's that would occasionally throw the three codes:

REDUCED ENG. POW. MESSAGE ALONG W/ PARTIC. PWRTRAIN #87-65-16 - (03/24/1998)
SUBJECT: REDUCED ENGINE POWER MESSAGE ALONG WITH PARTICULAR POWERTRAIN
TROUBLE CODES (INSTALL NEW TAC-MODULE IF STRATEGY IN SERVICE MANUAL FAILS)
MODELS: 1997-98 CHEVROLET CORVETTE WITH 5.7L V8 ENGINE (VIN G - RPO LS1)
CONDITION #1: INTERMITTENT REDUCED ENGINE POWER EVENT, ACCOMPANIED BY
P-1516, OR P1518 TROUBLE CODES.
IF A SITUATION ARISES WHERE A P-1516 TROUBLE CODE IS ACCOMPANIED BY A
P-1120 AND/OR P-1220 TROUBLE CODE, THIS SERVICE BULLETIN DOES NOT
----------------------------------------------------------------- APPLY. IN
THESE CASES THE TECHNICIAN MUST USE THE NORMAL STRATEGY
------------------------------------------------------------------ BASED
DIAGNOSTIC. -----------------
CONDITION #2: INTERMITTENT REDUCED ENGINE POWER ACCOMPANIED BY TROUBLE CODE
P-1125 AND ANY OF THE FOLLOWING TROUBLE CODES:
P-1276 P-1281 P-1286
CAUSE:
CONDITION MAY BE DUE TO DIAGNOSTIC SOFTWARE AND CALIBRATION IN THE
TAC-MODULE WERE NOT OPTIMALLY UTILIZED.
CORRECTION:
IF THE ABOVE CONDITIONS CANNOT BE CORRECTED USING THE NORMAL STRATEGY BASED
DIAGNOSTICS LISTED IN THE SERVICE MANUAL, INSTALL THE NEW TAC- MODULE LISTED
BELOW.
PART INFORMATION:
NEW TAC-MODULE PART # 25319443
PARTS ARE EXPECTED TO BE AVAILABLE ON APRIL 6, 1998 FROM GMSPO.

Bought my '98 brand new and it did this several times during the first year. Oddly after resetting the codes it was fine and hasn't done it since (knock on wood!)

Robbie Curlee
Barnwell, SC

 

Robbie

Man, I wonder if were related? All of my family and relatives are from North and South Carolina!!:thumbs:
Well, anyway, I tried the throttle body cleaning and that did not help. The TSB is probably what is wrong with mine and it looks like I will need to get a new one.
I wonder how much they are??

Thanks for the reply

Bill Curlee


[Modified by Bill Curlee, 5:55 PM 1/26/2004]