ryanfive

Hello All, I have a 1990 coupe. I just had the trans rebuilt now a new problem has popped up. When I put the key in the ignition and turn it (with out starting) my fan turns on. It will either continue to run or shut off after a minute or two. The car will either start and run for a minute and then just shut off or it won't start at all. Also, if the car is running it will just shut off at random. I have a 25 minute drive to work and last night it shut off on me 3 times on the way to work. When I pulled over to restart the car it would take 4 or 5 times to get the car running again. I did notice that next to my speedometer it will flash SYS. Im getting very frustrated. Please can anyone help? Thank you,

Ryan-- Fort Myers, FL

94z07fx3

I don't know the L98 or the MY 1990 cars. With that said I will tell you that when this happened very similar but not exactly the same to our MY 1992 the final fix was a computer off of a F-body that I bought on eBay.

First things first check the codes to see if the comp is talking to the CCM/BCM (assuming that 1990's have seperate computers for those functions) there will be stored codes indicating a communication failure.

Check the grounds near the battery just inboard of the battery there are two. Disco scuff and reconnect use star washers if none are there now.

If you search my posts for flashing sys you'll see more detail. I am sure that some L98 guy will post more and better info soon. But checking the grounds costs you nothing and won't hurt anything.

Hooked on Vettes

If the problem started after the transmission repair, they
probably forgot to re-install the braided ground strap.

If you look at the negative battery cable at the battery
it splits into two cables.

One cable bolts to the engine block above the oil
filter. The other cable bolts to the frame along
with a braided cable. If you look at the frame
in between the engine and the power brake booster
below the firewall you should see the braided cable.

The other end of the braided cable bolts to one of the
engine to transmission bell housing bolts on the driver side.

ryanfive

Ok, I replaced 1 wire with a 20amp fuse that looked a little ragged. This wire was behind the battery with a bunch of other wires hooked onto a post. I then check the braid strap and everything was status quo there. The car fired right up and shut off a couple times. I restarted and the car ran perfectly fine for 10 minutes then I shut it off. I just got curious again, (few hours later) walked out to the car fired it up. I was happy until it shut off and the fan kicked on again. I looked on the dash next to the speedo and it was flashing SYS again. Any other things I can try to get this thing running? Thanks, Ryan

Hooked on Vettes

Did this problem occur right after the trans. was worked
on?

There shouldn't be a 20 amp. fuse at the battery jumper
block unless someone installed it in place of a fusible
link.

The battery jumper block is the battey power distributon point for most of the electrical system.

The Sys indicates the CCM has set a trouble code.
To find what the code is you need to short pin A to
Pin G on the diagnostic connector.

Here's the procedure towards the bottom of this
thread. In this case he needed to pull codes because
the Service Engine Soon indicator was coming on.

http://forums.corvetteforum.com/1582473223-post3.html

XR_Strider_GuY

ryanfive,
I would follow hooked on vettes procedure. When you ground terminal A&B you should get a 12, 12, 12 flash by the service engine soon light and then if there is an error code in the ECM and then it will return a 12 12 12 as an end.

My 1990 acted up like yours when my ECM quit. Infact only was i getting a sys when I did fire up after a few cutouts I found that the speedo was not working on occasion.

When I tested the car in the drive way, I was able to make the car stumble and stop by tapping on the ECM. If your issue is the ECM, its not the end of the world, just make sure you get a replacement "working" ECM for your 1990 and the suitable transmission and diff.

94z07fx3

One more free test:

Look inside the car just above the gas pedal for a bunch of wire that bend around a black metal bracket. Make sure that they haven't been scuffed by the edge of that metal to the point they intermittently short to ground.

ryanfive

Morning all, yesterday when I went to leave work the car was dead. I ran up and got a new battery and car fired up. I took car to auto store and they tested my charging system. Result came back with a dead alternator. I replaced the alternator and I still have the same dang problem. Today I will try hookedonvettes procedure and see what happnens. I will also take a look at the wires under dash. Thanks for all your guys help and I will report back with my find. Ryan

ryanfive

Ok, I pulled the codes on the car. In 4.0 Im pulling 42 EST System Error and
51 MEM-Cal Error

How do I fix these issues? Thanks again. Ryan

ryanfive

ok going to the store to buy a ECM which is about $100. not bad if it fixes the issue. ill keep you all posted. ryan

Hooked on Vettes

First disconnect the negative battery cable.

Re-seat the electrical connector plugs at the ECM.
Unbolt the ECM and flip it on it's back.
You'll see a metal plate held on by two bolts.
Remove the cover and you'll see a small circuit board.
On the end of the circuit board are the ejector tabs. If you
press on the tabs the circuit board will pop out
of the mother board. Verify no pins on the mother board
are bent. This circuit board is the Memory Calibration
chip which contains the engine calibration parameters and the
circuitry for limp home mode.

The board rarely fails. So re-seat it.

Start the engine . While the engine is running,
pull/move the wiring harness around the ECM connectors.
Bang on the ECM case.
Verify a loose connection is not causing the problem.

I've also posted the procedure to trouble shoot the EST
error. It requires some testing with a meter and test light.

If you notice in the EST trouble shooting chart it does say
a Mem Cal problem can cause a code 42. It also notes
both of your problems could point to a bad ECM.

You said SYS was blinking on the LCD but no code for the CCM
was set (Module 1). This usually indicates a low charged battery.

gmboileau

When you turn the key on power is supplied to the primary coolant fan relay which then waits for a ground source from the ECM to energize the relay and turn the fan on at a prescribed coolant temp.

I your case since the fan comes on right away it's getting a ground signal at the wrong time.

The relay could simply be faulty and fused in the closed position. Check that first.

The ground signal is carried on a Lt Blue/Black wire from connector C137 located near the ECM. If it is chaffed and finding a ground source that will turn on the fan regardless of the coolant temp.You can check with an OHM meter at this connection to see if there is a short to ground.

If the ECM is sending a ground source at the wrong time then the ECM or memcal is faulty.

ryanfive

Wholly Crap what a day. I started at 8 this morning surfing the forum for answers, had breakfeast and then moved to actual physical work on this car. Here is what i got......I went and bought an ECM, installed it and car ran like shi#! The engine was reving way way too high, the tach was bouncing all over the place and I even thought I heard a minor back fire. I went back to auto store, took off ECM in parking lot and traded it in for new one in hopes that it was defective. Installed new one. Car cranked up and purred like its supposed to. I was over the moon happy. On the way home I stopped at my buddy's shop to return the simple tools I borrowed for the job. While there I shut the car off. We chatted for a few minutes then I got back in the car only for it to not start.... Man was I depressed. He brought out his multimeter after getting me started again and found that my "brand new one day old alternator" was not charging my battery which is one day old also. I couldn't beleive it. After little investagation we figured that my alternator power cable (red cable that is hooked to alternator) was making no connection to the ground post just behind the battery. I went as fast as possible home and my car shut down about 3 miles from my house, ofcourse in the pooring rain. Had a friend come pick me up to buy a new battery to get the car home. I changed this sucker in the crappy rain. Go figure. I got car home, re seated all wires on the post behind the battery and it seems that the car is running once again at optimum. Let's hope this vette behaves and has no more trouble. I've been through this thing about as much as a weekend wanna b mechanic can. Thanks to all of you for your help! This forum is a great tool and I am happy to be a part of it.

Roll on, Ryan

well, till I come back with another issue........