Blinking Theft Light, Engine won't start (solution)

[djewing]

2001 Expy 4x4, 4.6 (stock electrics, no aftermarket alarm etc)

Yesterday I couldn't get my car started.
The "theft" light was blinking rapidly and wouldn't stop, the engine would crank fast (good battery) but would not start. I didn't want to kill my battery so I looked online and tried the several solutions I found to no avail. (I heard everything from the key being bad to the PCM needing to be replaced) I then called AAA for a tow but was able to get it started instead.
Thankfully, the cure for me was pretty simple, maybe it will be for you too:

If you experience the same problem try checking in the fuse box in the engine compartment for dirty or corroded fuses. Also, there are 3 diodes at the front end of the box. One of those diodes is the "PCM Power Diode" and is the closest to the fender side of the fuse box. I was able to pull out, clean the sockets with contact cleaner and reset the mini fuses and diodes and the problem went away. One of the mini fuses (#2-30amp) is for the "PCM Power Relay". So I suspect the problem either being the diode or that particular fuse. I noticed that all the fuses/relays were somewhat corroded and dirty so I just pulled all of them and used contact cleaner to clean the sockets and reinserted new mini fuses. I inspected the maxi fuses and found they were all in decent shape so I cleaned and reinstalled them as well as the relays to hopefully prevent any other trouble down the road. *also* just an FYI: none of the fuses were blown. All were good, just had dirty legs and sockets.
Just thought I'd share. Hopefully this will help someone else.

 

[Bedrck47]

You got lucky.

You say all the fuses were good. How did you check them?

 

[1955moose]

You did get lucky, this could have been a tail chaser. Some don't agree with me, but I like to use a small dab of die electric grease on terminals of items that get exposed to moisture. The other option is to routinely remove fuses, and relays, and sand connections. Personally I'm too lazy to do that, so I grease them. Worked for me The past 40 years. I rarely have electrical gremlins.


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[docraymund]

Thanks for sharing! I will try to keep that in mind!

 

[djewing]

Yes, I certainly was lucky/fortunate it wasnt a bigger issue.

Bedrck47: I visually inspected the fuses and the little wire inside was still intact showing they were good. This was confirmed because at first I just reset them (remove and replace) and the car started. Which indicated to me it was due to the dirty/corroded terminal legs.
I decided when I got home that I would do a thorough cleaning to ensure reliability. I inspected all relays, fuses and diodes for corrosion and cleaned the sockets in the fuse box while deciding to replace all the mini fuses rather than spend the next hour cleaning terminal ends as they were all dirty and I had a bunch of fuses on hand.

1955moose: When I did need to clean terminals I used a brass wire brush to minimize damage to the terminal legs.
I've also used dialectic grease sparingly in moist areas with success.

Thanks for your replies.

 

[Bedrck47]

As I said you were lucky Looking at fuses to see if they LOOK good isn't a true test. Looks can be deceiving. Test light or Volt meter is a better test That proves the fuse is good and also shows voltage present. .

 

[Opsimath]

Last time this happened to me I was camping and accidentally went swimming with the key. Turns out the electronics in the key don't like water (why aren't they waterproof?) so the car didn't recognize it and refused to start. Luckily we brought two cars that weekend and were able to send the other one home to get the spare key.

 

[1955moose]

I keep a spare chip key hidden with mine, just in case. Yeah no kind of electronics seems to like moisture. I agree they should be water tight. Think of how many things we do around water with key ring in hand.


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