• Mustang Forums
  • 1996 - 2004 SN95 Mustang -General/Talk-
  • SN95 4.6L Mustang Tech

Anti-theft mode

  • Thread starter Thread starter Andresquintana.mma
  • Start date Start date Apr 29, 2021

Andresquintana.mma

Active Member
Nov 28, 2014
207
21
28
Apr 29, 2021
#1
  • Apr 29, 2021
  • #1
Hey everyone I bought a 2004 mach 1 roller and got a 2004 mach 1 engine for the body got everything installed the body was an auto and I converted it to standard it still has auto computer, I think the guy had a lightning engine in the car before I got it from what I was told. Got mostly everything put together and wanted to see if it would turn on went to crank and the theft light is flashing. It cranks but wont start, did some research and tried various things like leaving the key on the on position for 10 min then try to start it the light would stop flashing then when I cranked it would start flashing again, disconnected the battery and tried a few other things. If any one knows how to get it out of anti theft mode Id appreciate it, maybe I didnt plug something in on the harness? Im not to sure first sn95 Ive worked on. If not Ill try the dealer Thanks in advance.
 

wmburns

SN Certified Technician
Aug 14, 2009
5,892
514
204
Houston Texas
Apr 29, 2021
#2
  • Apr 29, 2021
  • #2
The "turn the key on for 10 minutes" is a GM thing.

Turn the key on but do NOT crank. Does the theft light go out after a 3 second "prove out"? If not, STOP and find out why.

If the theft light does go off after the 3 second "prove out", then your problem is not PATS related.

ForScan ODB2 scanner w ELM327 USB

ForScan ODB2 scanner w ELM327 USB

While working on your car have you ever wanted: to find an ODB2 operational PID value (say fuel pressure or MAF)? How about graph a PID value over time? Or compare multiple PID's over time? Access a bi-directional PCM control such as test a...
www.stangnet.com
 

Andresquintana.mma

Active Member
Nov 28, 2014
207
21
28
Apr 29, 2021
#3
  • Apr 29, 2021
  • #3
wmburns said:
The "turn the key on for 10 minutes" is a GM thing.

Turn the key on but do NOT crank. Does the theft light go out after a 3 second "prove out"? If not, STOP and find out why.

If the theft light does go off after the 3 second "prove out", then your problem is not PATS related.

ForScan ODB2 scanner w ELM327 USB

ForScan ODB2 scanner w ELM327 USB

While working on your car have you ever wanted: to find an ODB2 operational PID value (say fuel pressure or MAF)? How about graph a PID value over time? Or compare multiple PID's over time? Access a bi-directional PCM control such as test a...
www.stangnet.com
Click to expand...
Thanks for your reply I’m not exactly sure what “prove out” means. I turn the key on and it still flashes same speed after 3 seconds. It’ll take about 4-5 min for the theft light to slow down the flashing and eventually stop. If I do anything like try to crank or take the key out the light will continue to flash.

damn YouTube lying to me haha they did the 10 min thing on a mustang and claimed it worked. Should I buy an OBD2 scanner?
 

Andresquintana.mma

Active Member
Nov 28, 2014
207
21
28
Apr 29, 2021
#4
  • Apr 29, 2021
  • #4
wmburns said:
The "turn the key on for 10 minutes" is a GM thing.

Turn the key on but do NOT crank. Does the theft light go out after a 3 second "prove out"? If not, STOP and find out why.

If the theft light does go off after the 3 second "prove out", then your problem is not PATS related.

ForScan ODB2 scanner w ELM327 USB

ForScan ODB2 scanner w ELM327 USB

While working on your car have you ever wanted: to find an ODB2 operational PID value (say fuel pressure or MAF)? How about graph a PID value over time? Or compare multiple PID's over time? Access a bi-directional PCM control such as test a...
www.stangnet.com
Click to expand...
Oh ok sorry for not understanding but you explained it already ‍ Haha but yeah the light stays flashing for sure. So it’s not just proving out.
 

Andresquintana.mma

Active Member
Nov 28, 2014
207
21
28
Apr 29, 2021
#5
  • Apr 29, 2021
  • #5
Had a locksmith come try and flash the keys but the theft light kept coming on. So didnt work. does any one have a diagram for the mach 1 with an egr delete? Looks like Im going to have to take it to get tuned or to Ford.
 

wmburns

SN Certified Technician
Aug 14, 2009
5,892
514
204
Houston Texas
Apr 30, 2021
#6
  • Apr 30, 2021
  • #6
Andresquintana.mma said:
Should I buy an OBD2 scanner?
Click to expand...
Just wondering. Did you look at the cost of the USB dongle? Less than $30.

What did the service call by the locksmith cost?

But what do you think the cost of taking the car to the dealer will be?

Do you own (or know someone) with a Windows laptop?

The ODB2 scanner has the ability to also read any DTC that may be stored in the body control modules. Is it possible that there's a DTC stored inside the cluster module that gives you "the clue" that provides the key to your problem? Maybe. Is it possible that the "live data" feature of the ODB2 scanner could help you trouble shoot your problem? IMO that depends upon you.

So if asking for my opinion. The value of using an ODB2 scanner to trouble shoot cars once learned is a game changer. Is to going to "tell" you what is wrong with your car? No. It's still up to you to understand what story the ODB2 scanner is telling you. But for only $30 how wrong could you go?
 

Andresquintana.mma

Active Member
Nov 28, 2014
207
21
28
May 1, 2021
#7
  • May 1, 2021
  • #7
wmburns said:
Just wondering. Did you look at the cost of the USB dongle? Less than $30.

What did the service call by the locksmith cost?

But what do you think the cost of taking the car to the dealer will be?

Do you own (or know someone) with a Windows laptop?

The ODB2 scanner has the ability to also read any DTC that may be stored in the body control modules. Is it possible that there's a DTC stored inside the cluster module that gives you "the clue" that provides the key to your problem? Maybe. Is it possible that the "live data" feature of the ODB2 scanner could help you trouble shoot your problem? IMO that depends upon you.

So if asking for my opinion. The value of using an ODB2 scanner to trouble shoot cars once learned is a game changer. Is to going to "tell" you what is wrong with your car? No. It's still up to you to understand what story the ODB2 scanner is telling you. But for only $30 how wrong could you go?
Click to expand...


I have some usb dongles laying around not to sure if they are the ELM237 USB dongle but if not I can run to best buy I ordered the scanner off amazon should be here tomorrow hopefully. Yes I have a laptop I jsut wanted it to work asap. I still want to learn the OBD2 scanner I have a scanner for my foxes and it saves so much time!

Locksmith charged me 30 because he couldn't get it going and the friend who sold me the roller put me in touch with original owner. He says the theft light has always been on and the car worked fine. Told me the PATS was turned off in his tune. I was also missing the plug to the crank case sensor and he told me I wouldn't get spark if that wasn't plugged in (Im so new to mods). Plugged it in and the car wants to start up now I just need to make an EGR delete plate and run the vacuum. By any chance does anyone have a diagram for the vacuum hoses for an 04 mach 1? I believe the car will start now but will probably run rich due to the tune from previous owner.

This is really the only thing I saw on the internet for vacuum on a mach 1 not sure if this is right but its all I have to go by.
 

Andresquintana.mma

Active Member
Nov 28, 2014
207
21
28
May 1, 2021
#8
  • May 1, 2021
  • #8
Mocked up the vacuum and blocked off the egr. Car started but wouldn’t stay on unless I hold the gas. I still need to get the valve cover lines. So maybe that will fix it and possibly a tune.
 

wmburns

SN Certified Technician
Aug 14, 2009
5,892
514
204
Houston Texas
May 2, 2021
#9
  • May 2, 2021
  • #9
I once own a 1996 Mustang GT that couldn't be driven after disconnecting the battery. It would die as soon as it was put into drive. Impossible to even get it out of the driveway.

The solution? Allow the PCM to re-lean the IAC idle trim values. Once done the car drove normally until the next time the battery was disconnected. For the 1996 the IAC relearn involved allowing the car to idle for one full minute at full operating temperature. Repeat one minute idle with the AC on.

Regarding your problem there a TONS of possible "causes". This is where an ODB2 scanner with access to "live data" can really earn it's keep. For example:
  • What is the MAF flow? Does the MAF change during cranking or when the throttle is changed?
  • What is the IAC duty cycle?
  • What is the IAT value? Is it "plausible" based upon current out door temperature?
  • What is the ECT value? Is it "plausible?"
  • What is the fuel pressure?
  • What is the operating mode of the PCM (open or closed loop)?
  • Are the front O2 sensors sending any data?
 
You must log in or register to reply here.

Similar threads

J
Car won’t start
  • JLB
  • Nov 15, 2025
  • SN95 4.6L Mustang Tech
Replies
4
Views
220
SN95 4.6L Mustang Tech Nov 15, 2025
nickyb
B
Resolved 1996 PATS help needed
  • Bajaboy
  • May 21, 2025
  • SN95 4.6L Mustang Tech
Replies
5
Views
516
SN95 4.6L Mustang Tech May 23, 2025
Bajaboy
B
D
Anti theft mode
  • Danny holcomb
  • Oct 9, 2025
  • 1996 - 2004 SN95 Mustang -General/Talk-
Replies
6
Views
186
1996 - 2004 SN95 Mustang -General/Talk- Oct 10, 2025
manicmechanic007
T
2001 GT 4.6 V8 weak crank no start.
  • The-Bamboo-Farmer
  • Nov 12, 2025
  • 1996 - 2004 SN95 Mustang -General/Talk-
Replies
2
Views
173
1996 - 2004 SN95 Mustang -General/Talk- Nov 13, 2025
The-Bamboo-Farmer
T
L
1997 V6 Starting issue
  • leanzik04
  • Mar 20, 2026
  • SN95 V6 Mustang Tech
Replies
3
Views
205
SN95 V6 Mustang Tech Mar 20, 2026
Noobz347
Share:
Bluesky Email Share Link
  • Mustang Forums
  • 1996 - 2004 SN95 Mustang -General/Talk-
  • SN95 4.6L Mustang Tech
Menu
Log in

Register

  • Forums
  • What's new
  • Media
  • Resources
  • Contact
  • Sponsor
X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?

X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?