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Ford F150 Theft Light Blinking Won’t Start – [9 Troubleshooting Methods]

Your Ford F150 theft light blinking won’t start? I know how frustrated you are. Don’t worry! I am here to help you fix your truck.

In this article, I have discussed the possible reasons for this problem and how to troubleshoot it.

If your Ford F150 doesn’t start and the theft light blinks rapidly, the PCM power relay is the most common reason for this problem. Other reasons can be bad key transponder, dead key fob battery, bad fuses, and bad PCM.

Please Note: You can follow this guide for any Ford F150 regardless of the model and year.

Common years with this problem are: Ford F150 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2007, 2008, 2009, 2010.

Before trying any of the following troubleshooting methods, disconnect the battery and wait for about 10 to 15 minutes as a first solution. Then reconnect the battery, and see if that solves this problem.

And if that doesn’t work out, try to figure out the fault codes associated with the actual problems.


The Two-Digit PATS Fault Code or DTC (1 : Flash Count)

While the ignition is ON, you may see dashes in the odometer, and the theft light keeps blinking. It’s telling you a code associated with the problems you need to fix. So how do you find the code?

First, the light will blink rapidly for about 30 to 45 seconds and go off. Then it will flash for once and will pause for a few seconds.

Finally, it will blink a few more times (1 to 6 times) at a regular pace, and you need to count those final blinks.

Let’s say the count is six. Then it’s the trouble code 16. If there are multiple problems, the light will again repeat the pattern to represent a different code. 

And each of the fault codes signifies a different problem with your Ford F150. For example, see the DTCs in the following table.

Diagnostic Trouble CodeDescription
B1213Less than 2 (or 3 if equipped w/Valet key) keys programmed to the system.
B1232/B2103Transceiver internal antenna damaged. Replace transceiver.
B1342ECU is defective (EEPROM in PCM is not working — replace PCM). PATS related when stored in PCM only.
B1600Non-PATS Key or damaged key.
B1601Unprogrammed encoded ignition key detected (leave ignition on for 20 seconds before trying a programmed key, in Anti-Scan Mode).
B1602Partial detection of encoded ignition key.
B1681Transceiver signal not detected.
B2141Non-Volatile Memory (NVM) configuration failure — No PCM ID stored in PATS.
B2139/U2510PCM ID does not match between the PCM and PATS control (PATS/ICM/VIC/HEC/SCIL).
B2431Key program failure (defective key or transceiver).
U1147/U1262Communications issue, SCP (J1850), between PCM and PATS control (PATS/ICM/ VIC/HEC/SCIL).
U1900/U0100 U2511/B2009Communications issue, CAN (J2284), between PCM and PATS control (ICM).
P1260PCM disabled the vehicle because of a PATS concern. Retrieve DTCs from applicable PATS control function.

9 Reasons Why Ford F150 Theft Light Blinking Won’t Start

Now, here are the possible problems and solutions to the problem of Ford F150 won’t start and the theft light blinking.

ProblemSolution
Bad key transponderTry with another key
Unprogrammed keyTry with a programmed key
Dead key fob batteryReplace the key fob battery
Damaged door lock cylinderReplace the door lock cylinder
Bad fusesReplace the bad fuses
Bad PCM power relayReplace the PCM power relay
Bad PCM power diodeReplace the PCM power diode
Bad fuel pump relayReplace the fuel pump relay
Bad PCMReplace the PCM

1. Key Transponder Issues

Sometimes, your transponder key can trigger the PATS (Passive Anti-Theft System) that immobilizes the engine.

If you have any metal objects or electronic devices on the same keyring you put your truck key on, that might interfere with the microchip of the transponder.

So remove all these objects, and start the engine, which may solve this problem.

Another reason could be the transponder chip is damaged. If you’re trying to start your engine with a bad transponder key, the theft light starts flashing, and the engine won’t start.

Try with your other keys, and if it starts the engine, the previous key has a transponder issue and is probably a damaged key.

2. Unprogrammed or Wrong Key

Did you program a spare key recently? Did you have all the existing keys with you in the cab?

If you didn’t, then all the absent keys are now incompatible, and the system can’t recognize them anymore. Hence the PATS got triggered!

In that case, you need to use a correctly programmed key to start the engine and reprogram those incompatible keys.

Also, you might be using the wrong key! Make sure that is not the case.

3. Dead Key Fob Battery

You should check out the battery if you’re using a key fob. The dead battery can cause this issue.

Replace your key fob’s battery, which may disable the theft light.

4. Damaged Door Lock Cylinder

If this anti-theft flashing issue happens on an older generation of Ford F150, there is a chance the door lock cylinder is damaged.

Check whether you can latch the door properly, and if the locking cylinder is not latching, the PATS senses it as a theft attempt.

So replace the door lock cylinder, which will stop triggering the PATS.

5. Bad Fuses

Open the fuse box (battery junction box) under the hood, and test the fuses. You can start with the number 18 fuse (15 Amp).

There might be one or multiple blown-out fuses that are causing this problem. Replace them, and you may get your truck running fine.

And, don’t forget the fuses in the central junction box inside the cabin. Test those fuses as well. You can start with the number 2 fuse (5 Amp).

6. Bad PCM Power Relay

The Powertrain Control Module is one of the most critical components for your engine to work properly. And the PCM power relay is a part of that.

If the relay doesn’t work or malfunctions, there will be no communication between the engine and the PCM. Hence the theft light will start flashing.

So you must check the PCM relay if your Ford F150’s theft light keeps blinking and doesn’t start. You can try swapping it with another identical relay and see if there are any changes in the behavior.

If the relay is damaged, you need to get a new PCM relay to solve the problem.  

7. Bad PCM Power Diode

The PCM power diode keeps the voltage running only one way towards the PCM power relay, and if the diode is damaged, there might be issues in the circuit. 

So it’s essential to check whether it’s in good condition. And it’s replaceable.

8. Bad Fuel Pump Relay

The fuel pump receives power when the fuel pump relay works appropriately. So, ensure the fuel pump relay sends power to the pump.

If it’s a bad relay, you need to replace it, which should solve the problem.

9. Bad PCM

If none of the solutions I have mentioned above is solving the issue. Then it might be the PCM itself.

If there are dashes in the odometer, and no communication with your scan tool, then it’s probably a bad PCM issue.

So go ahead and replace the PCM. You must perform the parameter reset or relearn procedure to allow the new PCM to work.

And this should disable the theft light blinking and allow your engine to fire up.


Final Words

So there you have it. I have discussed all the potential causes and the troubleshooting methods for the Ford F150 theft light blinking won’t start.

If you have had no luck with the suggested methods, you need to go the expensive route: visit the dealership or contact an expert mechanic.


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Kevin Shaw

Editor-in-Chief at F150Lab

Kevin Shaw has a vast knowledge of pickup trucks, especially the Ford F150. He has been doing various DIY fixes, upgrades, and modifications to pickup trucks for more than five years now.

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