Vats bypass
Melting Slicks
Joined: Nov 2016
Posts: 2,256
Likes: 3,082
From: So Cal
2023 C4 of the Year Finalist - Unmodified
What Year?
86-91: Jumper A&B in the diagnostic connector and turn the key to RUN. Watch the Service Engine Soon light for Code 46. If present, VATS is not sending the signal for injection. Or the ECM is not receiving the signal because of a loose connection or rodent-damaged wire. Code 46 is only present when the Fuel Enable signal is not present. 46 is not a "stored code".
92-96: Turn key to RUN. The SECURITY light must be OFF. If it is Solid-On (not "flashing" like it does with a door open), VATS is not sending the Fuel Enable signal to the ECM. If SECURITY is flashing is groups of 3 silmitaniously with a 3-flash of SYS, the ECM/CCM Fuel Enable handshake failed. This is rather rare, except for a 92, and occasionally a 93.
Ok. I remember now. I found this thread. I found and reviewed it. It looks like you had it running? What changed?
Last edited by IHBD; Dec 30, 2025 at 05:01 PM.
Thread Starter
Instructor
Joined: Jun 2025
Posts: 139
Likes: 2
I don't know what has changed. That's what I'm trying to figure out. I had a vats problem to start with. The link you posted on the bypass I had one of those and I couldn't get it to work so I purchased a Painless bypass. It worked fine until this happened. It has the same symptoms. The truck was running great on cold start up but would not start when warm. I'm talking running for less than 2 min. In the process of trying to figure what was causing that it stopped running, I have checked or replaced each and everything but I haven't found the cause. Using a noid light the injectors is not firing. I'm going to check the current to the injectors today. I'm also going post a new thread telling all that I have done.
If it's a vats problem would it give a code
If it's a vats problem would it give a code
Last edited by snackstick; Dec 31, 2025 at 11:00 AM.
Thread Starter
Instructor
Joined: Jun 2025
Posts: 139
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I have a flute multimeter that reads HZ. I know where B6 pin is located. I just not sure how to use the multimeter to read the pin. do I use the black lead for ground and red lead to probe the pin. please be patient, I'm not a tech guru, that's why I'm here
Le Mans Master
Joined: Jul 2004
Posts: 6,228
Likes: 698
From: Clifton Park, NY ............Clearwater, FL ... 85 Original Owner
I don't know what has changed. That's what I'm trying to figure out. I had a vats problem to start with. The link you posted on the bypass I had one of those and I couldn't get it to work so I purchased a Painless bypass. It worked fine until this happened. It has the same symptoms. The truck was running great on cold start up but would not start when warm. I'm talking running for less than 2 min. In the process of trying to figure what was causing that it stopped running, I have checked or replaced each and everything but I haven't found the cause. Using a noid light the injectors is not firing. I'm going to check the current to the injectors today. I'm also going post a new thread telling all that I have done.
If it's a vats problem would it give a code
If it's a vats problem would it give a code
Melting Slicks
Joined: Nov 2016
Posts: 2,256
Likes: 3,082
From: So Cal
2023 C4 of the Year Finalist - Unmodified
Is Code 46 back and present? If = NO, the bypass is functioning and the 30 Hz is correct. In his first post he says there is no Code 46 again. It doesn't look to me, based on what he's saying the symptoms are, that it is a Fuel Disabled problem. Ie, it is not "VATS".
Does it fire on starting fluid? (You're testing for spark, and whether there are reference pulses which are needed for both spark and injection.) If = NO:
Does the fuel pump run briefly when the key is turned to RUN, then stop? Leave key in RUN and briefly crank. Does the fuel pump run again and stop? << If = NO, there were no reference pulses. You have a basic distributor problem. No spark, and no reference pulses = no injector pulses.
Does it fire on starting fluid? (You're testing for spark, and whether there are reference pulses which are needed for both spark and injection.) If = NO:
Does the fuel pump run briefly when the key is turned to RUN, then stop? Leave key in RUN and briefly crank. Does the fuel pump run again and stop? << If = NO, there were no reference pulses. You have a basic distributor problem. No spark, and no reference pulses = no injector pulses.
Last edited by IHBD; Jan 2, 2026 at 05:35 PM.
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Melting Slicks
Joined: Nov 2016
Posts: 2,256
Likes: 3,082
From: So Cal
2023 C4 of the Year Finalist - Unmodified
Do you have Code 46? (I've asked this at least 6-8 times over the past year and a half.) If = no, you do NOT have a "VATS" (or bypass) problem. It is something else.
Last edited by IHBD; Mar 24, 2026 at 11:39 PM. Reason: Removed the INCORRECT reference to FE frequency.
Melting Slicks
Joined: Aug 2003
Posts: 3,401
Likes: 396
From: Lakeville MI
I know I posted this in the other thread. The acceptable range is 33-66 hz. Some VATS bypass devices can output either 30 hz or 50 hz. Use the 50 hz setting.
LC00E FDB 3277 ; VATS Ck Value, Fail if VATS G.T. 66Hz
LC010 FDB 1638 ; VATS Ck Value, Fail if VATS L.T. 33hZ
LC00E FDB 3277 ; VATS Ck Value, Fail if VATS G.T. 66Hz
LC010 FDB 1638 ; VATS Ck Value, Fail if VATS L.T. 33hZ
Racer
Joined: Jul 2016
Posts: 296
Likes: 14
From: New York
Or buy the burn 2, chip adapter, and blank chip from moates and do it yourself
https://shop.moates.net/products/burn2-chip-programmer
Melting Slicks
Joined: Nov 2016
Posts: 2,256
Likes: 3,082
From: So Cal
2023 C4 of the Year Finalist - Unmodified
If he's using the timers.shop signal generator the blue and green wire should be not connected to anything (taped off) for 50Hz. If the blue wire is connected to ground, that's his problem.
Thread Starter
Instructor
Joined: Jun 2025
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I don't have a code 46. I do know that the engine will start and then immediately shut down. it will do this over and over until i change the vats bypass and it will start up and run as it suppose to. I'm on my third bypass. getting tired of buying them.
Supporting Vendor
Joined: Nov 2025
Posts: 274
Likes: 33
From: Cotopaxi, Colorado
why not permanently delete it ?
__________________
Supporting Vendor
Joined: Nov 2025
Posts: 274
Likes: 33
From: Cotopaxi, Colorado
https://tunedperformance.org/store/p/gm-vats-delete
if you can mail in your memcal, i not only delete vats but if older tune i update the tune accordingly.
if you can mail in your memcal, i not only delete vats but if older tune i update the tune accordingly.
Supporting Vendor
Joined: Nov 2025
Posts: 274
Likes: 33
From: Cotopaxi, Colorado
vats kills injector pulse if it’s not working.
Thread Starter
Instructor
Joined: Jun 2025
Posts: 139
Likes: 2
can anyone recomend a good set of 22# injectors that won't break the bank. I have purchased one sent that was not good. I have had my factor set refurbished. it seems that I have one or more bleeding. fuel pressure goes from 45 psi to 0 in a mater of a few seconds. I have checked the fpr with no sigh of leaking. I have removed the TPI and raised the fuel rail up to see the bottom of the injectors and applied 45 psi with no sign of bleeding. I have removed the 9th injector with no sigh of bleeding. I have added a check valve in the input fuel line.I have pinched off the return fuel line.
I have a no start issue when warm that I haven't resolved after doing everthing that was recommended on this site.
I have a no start issue when warm that I haven't resolved after doing everthing that was recommended on this site.