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Greetings from the C6 section!
The VATS on my Uncle's 86 has given up, and I'm planning to install one of the frequecy-generator bypass modules.
The instructions are a little vague as to which wire at the ECM is the fuel enable circuit that needs to be tapped.
Does anyone have wiring diagrams showing the ECM and BCM?
They would be greatly appreciated. Search function here on the forum sort of blows...
Greetings from the C6 section!
The VATS on my Uncle's 86 has given up, and I'm planning to install one of the frequecy-generator bypass modules.
The instructions are a little vague as to which wire at the ECM is the fuel enable circuit that needs to be tapped.
Does anyone have wiring diagrams showing the ECM and BCM?
They would be greatly appreciated. Search function here on the forum sort of blows...
Provide a link to the product you've purchased. There's a couple. So you have 'crank' but suspect no fuel enable? There isn't a BCM in the '86. '86 was first year and there were changes to ignition cylinder and key blank used. If you have 'crank' it could be assumed you have only the fuel enable fault. Is the 'crank' function of VATS defeated by using a resistor currently?
Greetings from the C6 section!
The VATS on my Uncle's 86 has given up, and I'm planning to install one of the frequecy-generator bypass modules.
The instructions are a little vague as to which wire at the ECM is the fuel enable circuit that needs to be tapped.
Does anyone have wiring diagrams showing the ECM and BCM?
They would be greatly appreciated. Search function here on the forum sort of blows...
How did you determine that? Does it just not crank or are there more symptoms?
Thanks for the quick feedback, particularly the info about no BCM.
Classic VATS symptoms....
No crank, jumped the starter with a remote.
Cranks/fires/dies. He had the key tested for resistance, OK.
I'm remote, so can't do any hands on diagnosis, but not holding out any hope that it'll be fixed with the resistor bypass.
Thanks for the quick feedback, particularly the info about no BCM.
Classic VATS symptoms....
No crank, jumped the starter with a remote.
Cranks/fires/dies. He had the key tested for resistance, OK.
I'm remote, so can't do any hands on diagnosis, but not holding out any hope that it'll be fixed with the resistor bypass.
Aklim: It is probably firing on the cold start injector which ceases injecting when the key is turned back from CRANK.
The timers.shop unit is pretty good. I installed one in my 90 a couple of months ago and it has been flawless for the 6,000 miles since. (Yes, 6,000 miles in a couple of weeks. I went on a road trip.)
You need power, ground, and the cir 229 dk blue fuel enable wire at the ECM. These wires are available at the ECM under the RH dash.
C2, cavity A6, pink/ blk = IGN power with key in RUN or START.
C2, cavity B7, black = Ground.
C2, cavity B6, dk blue cir 229 = Fuel Enable input. NOTE: Either cut this wire and make the connection to the ECM-side wire, or remove the VATS module. I wouldn't 'back-feed' the VATS module with the Signal Generator, it may not be reliable. Remove the VATS module from the equation by cutting the blue wire.
On the Signal Generator(SG):
SG red = pink/blk (power)
SG blk = black (Ground)
SG blue (50hz) or green (30hz) to dk blue Fuel Enable.
Note regarding the frequency to use: Many GM ECMs use 50hz, which is the blue wire. Some use 30hz which is the green wire. My 90 used the 30hz, but it is a ZR-1, so the ECM may be different than the much more common 165 ECM that the 86 L89 uses. Connect the power and ground permanently. Connect the blue (50hz) loosely to the blue wire going into the ECM. Turn key to RUN. There is an LED in the timer. It should be flashing 2X, then off, 2X, then off, etc. This indicates the timer is outputting the 50hz signal. Try a start. If it starts and runs, you're done. If it does not stay running, turn key to OFF, and remove the SG blue wire. Attach the SG green wire to the ECM blue wire. Wait for the 5 minute timer to reset! Try it again, if it now stays running, you need the 30hz signal which is the green wire. The LED blinks 3X for the 30hz signal.
There are 2 additional outputs that use both the blue and green wires. There are installation instruction available online at the timers.shop website. You probably won't need these. I was told by the tech support at timers.shop "use what works" when I ended up with a non-documented wiring scheme for the Signal Generator, but it was working. I ended up going back into the dash and changing the wiring to the 30hz connection I outlined above. It has been working flawlessly.
Sorry for the TL;DR but everything you need to know about using the timers.shop device in an 86 is there.
This should 'lock' your response for future reference use by those wishing to use that device for 'fuel enable'.
For an '86 there seems to be maybe some questionable comments regarding ECM using an '86 FSM which I believe correct. Everything between the lines needs confirmed.
........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ...
You need power, ground, and the cir 229 dk blue fuel enable wire at the ECM. These wires are available at the ECM under the RH dash.
C2, cavity A6, pink/ blk = IGN power with key in RUN or START. C2, cavity B7, black = Ground. C2, cavity B6, dk blue cir 229 = Fuel Enable input. NOTE: Either cut this wire and make the connection to the ECM-side wire, or remove the VATS module. I wouldn't 'back-feed' the VATS module with the Signal Generator, it may not be reliable. Remove the VATS module from the equation by cutting the blue wire.
........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ .........................
OP - so you've not done any diagnostics 'what so ever' - you mentioned holding out 'no hope' for resistor by-pass!! I sent you a PM last evening and haven't seen a response to it yet!
Based on my own experience and what I've read about others having, seems like the biggest issue encountered is the resistor pellet on the key is not being read by the VATS system. Turn on the key and you get a security light on the DIC IIRC when the resistor isn't being read. It takes about 5 minutes or disconnecting the battery to reset the Security code. Sometimes cleaning up the contacts and the key will fix it temporarily, but it's crap on the key or contact that's the issues in this situation.
If that's your condition, here's what I did. I got a bypass dongle for the car. The one I got has only 1 resistor value so you need to read the resistor off the key when ordering. There's a 2 wire pigtail coming out of the bottom of the steering column, one wire is orange from what I remember that you'll be dealing with. There's a connector about 12" from the column, you disconnect that connector and plug the dongle into the wire going up behind the DIC, it's done. If that's your problem, you've solved it.
Here's the dongle I got for my 86: 86-89 Security Override System - Bypass The VATS (corvettecentral.com)
I used a 1988 FSM for the above ECM connections. AFAIK, the 86 and the 88 use the same 165 ECM. You have access to a 1986 FSM. Be helpful. If there are differences between what I posted and what you see in the 86 FSM, SAY SO!
So you 'guessed again' or maybe just 'misspoke' ?
See post #5 - I had already PM'd the OP with information and mentioned supplying him with creditable info. With an '86 not knowing whether it had any of the ignition switch and key replacements per the TSB there's much he needs to do to start! An '86 that's survived 35+ years without a VATS issue might be a 'stretch' but then again .........
NomakeWan was doing the same thing. (I wonder where that flash in the pan went? Probably violated his parole and is back in prison with no internet access.
Either that or he used his smart-*** condescending mouth on the wrong person and he is in an Orange hospital or long term care home.
Either that or he used his smart-*** condescending mouth on the wrong person and he is in an Orange hospital or long term care home.
Don't know but his last post was in June so maybe he has a summer thing going? Not sure who or what he is about so who knows? People come and go all day long. So. E take a haitus that turns permanent. It's like employees. Hobos. Here today, gone tomorrow.
Thanks for all the responses, guys!
Some were quite interesting...
As to my diagnostic work vs. guesswork:
Since I'm not anywhere near the car, I need to rely on the symptoms as reported to me.
This is not my preferred diagnostic method, but is the best I can do under the circumstances.
And my thoughts regarding the simple/easy resistor bypass 'repair'... Many (most?) others seem to have good success with the quick and easy repairs.
But after 40 years of auto repair (ASE certified Master Tech, BMW factory trained Master Tech...), quick and easy just doesn't seem to happen for me.
I was actually hoping someone had a schematic that I might look at!
Thanks for all the responses, guys!
Some were quite interesting...
As to my diagnostic work vs. guesswork:
Since I'm not anywhere near the car, I need to rely on the symptoms as reported to me.
This is not my preferred diagnostic method, but is the best I can do under the circumstances.
And my thoughts regarding the simple/easy resistor bypass 'repair'... Many (most?) others seem to have good success with the quick and easy repairs.
But after 40 years of auto repair (ASE certified Master Tech, BMW factory trained Master Tech...), quick and easy just doesn't seem to happen for me.
I was actually hoping someone had a schematic that I might look at!
An '86 requires some thought and different approach to diagnostics.. You still haven't responded to my PM with an email response! I was interested in helping because it's your Uncle. You need to start with actually measuring the length of the blade on an '86 key. You could carry his key to a dealer, a retailer and compare length to what's currently being sold. That would answer that question. It would be interesting also to know what the resistance was measured as. #1 .402K was abandoned very early because of issues, exactly when? Very early! If there's never been an attempt to just do a resistance replacement I'd first start by measuring the resistance at the column base and confirm there's no issues. I'd try a resistor there unless you could actually confirm 'crank' and know without a doubt that it's a fuel enable issue.
You want just a schematic or help?
*** I just found your email in my SPAM. That's a first guess it just didn't like the title! Email back to is leaving soon! I've been out most of the day doing gym and things! Your schematics should be there!!
I have an 86 with the timershop module installed. I spliced into the wiring near the VATs module, also bypassed the starter relay. Attached is the VATS wiring diagram for a 86. I spliced the 30hz output to the purple wire going to the ecm. For some reason I can’t find my notes so in the morning I will go and verify the connections, but I think the others are as expected ie, white to ppl wire (ecm), red to pink/blk (hot in run), black and blue to gnd.
8/8 checked and yes the above is the way it’s wired.
Last edited by Tod Stiles; Aug 8, 2021 at 11:42 AM.
Reason: Clarified connections
The start relay is in the middle of the dash above the radio.
remove the dash plastic to get to it.
turn the key to start, check the yellow wire for volts.
if no volts, pull the steering wheel down to the lowest position. Try it again.
chances are, the ignition switch which is moved from the key by a rod may be out of adjustment, or is worn out.
i speak from experience.
Go with the assumption that the starter is not getting power, use the voltmeter to confirm and work backwards, not the other way.
i have an 86, and the vats is working fine after 166,000 miles.
course, nobody has messed with this car but me.
1986 VATS help
